AP Chemistry Midterm

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What is the oxidation number for Cl in Cl2O (g)?

What is the oxidation number for Cl in ClO2 (1-) (aq)?

What is the oxidation number for Cl in ClO3 (1-) (aq)?

What is the oxidation number for Cl in HCl(g)?

-1

The valence electron configuration for an unknown element is xs2 xp4, where x is an integer. Predict the charge for the ion that would form when this element loses or gains electrons.

-2

How many moles of Na+ ions are in 100.mL of 0.100MNa3PO4(aq) ?

0.0300 mol

How many moles of Ni2+ are in 250.0 mL of 0.50 M NiSO4?

0.125 mol Ni2+

20.0 mL of HCL is titrated to an endpoint using 30.0 mL of 0.10 M NaOH. What is the molarity of hydrochloric acid?

0.15 M HCl

A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. The original solution used to make the solutions for the standard curve was prepared by dissolving 2.60g of CoCl2 (molar mass 130.g/mol) in enough water to make 100.mL of solution. What is the molar concentration of the solution?

0.200 M

If 28 g N2, 16 g O2, and 16 g CH4 are combined, what is the mole fraction of O2? If the total pressure of the mixture is 3.00 atom, what is the partial pressure of O2?

0.20; 0.60 atm

Calculate the volume of 1.25M lithium chloride solution that can be made with 13.3g of lithium chloride?

0.251L LiCl solution

What would be the concentration of chloride ion, [Cl1-] in a solution that is made by dissolving 10.0g zinc chloride, ZnCl2, in a solution that has a final volume of 500. mL?

0.294 M Cl1-

What is the nitrate ion concentration, [NO3]1-, in 100 mL of magnesium nitrate solution, Mg(NO3)2, that has 2.5g dissolved magnesium nitrate?

0.34 M NO

If a mixture is 3.0 mol O2 and 4.0 mol H2, what is the mole fraction of O2?

0.43

How many grams of CaCl2 (molar mass =111g/mol) are needed to prepare 100.mLof 0.100MCl−(aq) ions?

0.555 g

A sample of hydrogen gas at 27.0*C and 2.00 atm occupies a volume of 10.0L. How many moles of hydrogen gas are in the sample?

0.812 mol H2

A student incorrectly draws the particulate model of LiBr(s) on slide 14. Explain the student's error(s) in the particulate drawing.

1. The lithium ion is smaller than the bromide ion. The student should have drawn Li+ smaller than the Br-. 2. The Li+ and Br- ions should alternate within a row and column, otherwise the ions will repel each other.

A 500.mL aqueous solution of Na3PO4 (molarmass=164g/mol) was prepared using 82g of the solute. What is the molarity of Na3PO4 in the resulting solution?

1.0 M

How many grams of potassium hydroxide, KOH would be dissolved in 250mL of a 0.10M solution of potassium hydroxide?

1.4 g KOH

How many grams of NaCl (molarmass=58g/mol) are needed to prepare 100.mL of a 0.25M NaCl solution?

1.5 g

When a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 * H2O, is heated, H2O (molar mass 18g) is driven off. The mass of the anhydrous sodium sulfate (molar mass 142 g) that remains is 1.42 g. The value of x in the hydrate is what?

10.

A 2.4g sample of a mixture of calcium chloride, CaCl2, and sodium chloride NaCl, is found to contain 0.12g Na. What percent of this sample is NaCl?

13% NaCl

If 500.0 mL of 6 M H2SO4 is required for a lab, how many mL of an 18 M stock solution should be used for the dilution?

167 mL

What is the electron configuration for the Al ion?

1s22s22p6

Write the electron configuration for Aluminum ion, Al3+.

1s22s22p6

Write the electron configuration of fluorine ion, F-.

1s22s22p6

What is the electron configuration for S?

1s22s22p63s23p4

What is the electron configuration for S 2-?

1s22s22p63s23p6

Write the electron configuration for Calcium ion, Ca2+.

1s22s22p63s23p6

Write the ground state electron configuration for Arsenic.

1s22s22p63s23p64s23d104p3 or [Ar]4s23d104p3

Al(s)→Al3+(aq)+3e− Zn2+(aq)+2e−→Zn(s) The half-reactions for the oxidation-reduction reaction between Al(s) and Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients?

How many oxygen atoms are in 155 g of Ca3(PO4)2 (molar mass of 310 g/mol)?

2.41 x 10^24 atoms

C3H8(g) + 4Cl2(g) ---> C3H4Cl4(g) + 4HCl(g) A 6.0 mol sample of C3H8(g) and a 20. mol sample of Cl2(g) are placed in a previously evacuated vessel, where they react according to the equation above. After one of the reactants has been totally consumed, how many moles of HCl(g) have been produced?

20. mol

What is the average atomic mass of the element represented by the mass spectrum on slide 1? What is most likely the identity of this element?

24.3 u; Mg

Ni(s)→Ni2+(aq)+2e− Ag+(aq)+e−→Ag(s) What is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq) and Ni(s) based on the half-reactions represented above?

2Ag+(aq)+Ni(s)→2Ag(s)+Ni2+(aq)

Al(s)→Al3+(aq)+3e− Sn2+(aq)+2e−→Sn(s) Based on the half-reactions represented above, which of the following is the balanced ionic equation for the oxidation-reduction reaction between Al(s) and Sn2+(aq) ?

2Al(s)+3Sn2+(aq)→2Al3+(aq)+3Sn(s)

Write a net ionic equation for the reaction: 2KI (aq) + Pb(NO3)2 --> ???

2I(-1) + Pb(+2) ---> PbI2(s)

What is the electron configuration for Al 3+?

2s22p6

Based on provided calibration graph on slide 8, if the absorbance of an unknown concentration of the solution was 0.34, what was the molarity of the solution?

3.00x10^-6 M

CuSO4 solutions absorb light at a wavelength of 635 nm. Calculate the approximate energy of one photon of this light.

3.13x10-19J

What is the percent composition by mass of N2O4?

30.45% N and 69.55% O

A student analyzes a 2.00g sample of a mixture of copper, Cu, and aluminum, Al, by reacting the copper with nitric acid, HNO3 as represented in the equation above. The student determines that the reaction produces 0.010 mol Cu(NO3)2. Assuming that all of the copper in the mixture reacted completely, what was the percent of Cu by mass in the 2.00g sample of the mixture? Cu(s) + 4HNO3 (aq) --> Cu(NO3)2 (aq) + 2NO2(g) + 2H2O(l)

32%

What is the electron configuration for Al?

3s23p1

When the equation below is balanced and all coefficients are reduced to lowest whole-number terms, what is the coefficient for H3PO4(l)? Ca3(PO4)2(s) + H3PO4(l) ---> Ca(H2PO4)2(s)

What is the percent by mass of carbon in glucose, C6H12O6?

40.01%

What is the percent composition of sucrose, C12H22O11?

42.10% C, 6.49% H, and 51.40% O

A student uses visible spectrophotometry to determine the concentration of CoCl2(aq) in a sample solution. First the student prepares a set of CoCl2(aq) solutions of known concentration. Then the student uses a spectrophotometer to determine the absorbance of each of the standard solutions at a wavelength of 510nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510nm corresponds to an approximate frequency of 6×1014s−1. What is the approximate energy of one photon of this light?

4×10−19J

When a metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3 x 10-19 J. What is the frequency of light with photon energy 3.3 x 10-19 J? Calculate the wavelength for light with energy of 3.3x10-19J. What is the color of this light?

5.0x10^-14 sec-1; 6.0x10^-7 m; Orange

The diagram on slide 26 represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10−19J. What is the frequency of the light with photon energy of 3.3×10−19J? Using the wavelength information provided, what is the color of the light?

5.0×1014s−1; orange

Electromagnetic radiation with a maximum wavelength of 540nm(5.4×10−7 m) is needed for the study of the photoelectric effect in potassium atoms. What is the approximate frequency that corresponds to this wavelength?

5.6x10^14 s-1

In an experiment on the photoelectric effect, a photon with a frequency of 7×1014s−1 was absorbed by a sample. What is the approximate energy of this photon?

5x10^-19 J

When heated strongly, solid calcium carbonate decomposes to produce solid calcium oxide and carbon dioxide gas, as represented by the equation below. A sample of CaCO3(s) is placed in a rigid 35 L reaction vessel from which all the air has been evacuated. The vessel is heated to 437°C at which time the pressure of CO2(g) in the vessel is constant at 1.00atm. Calculate the number of grams of CaCO3(g) that reacted to produce the carbon dioxide gas. CaCO3(s) --> CaO(s) + CO2(g)

60. g CaCO3

What volume of a 0.100MHCl stock solution should be used to prepare 250.00mL of 0.0250MHCl?

62.5 mL

A 5.0g sample of a mixture of CaCO3 and SiO2 contains 1.5g of Ca. What is the percent CaCO3 in the mixture?

75% CaCO3

Based on their Lewis diagrams on slide 24, which of the following pairs of liquids are most soluble in each other?

The diagram on slide 17 shows the distribution of speeds for a sample of N2(g) at 25°C. Which of the graphs show the distribution of speeds for a sample of O2(g) at 25°C(dashed line) ?

A student was studying physical and chemical changes. The student carried out some procedures in the laboratory and recorded observations. For one of the procedures, the student concluded that a physical change took place, but not a chemical change. Which of the following could have been the results of the procedure? A A cube of metal was changed into a flat sheet of metal. B When two liquids at room temperature were combined in a beaker, the beaker became hot. C When two clear liquids were combined, the resulting mixture was cloudy. D When a colorless liquid was added to a blue liquid, the resulting solution was yellow.

A A cube of metal was changed into a flat sheet of metal.

Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g) A student combined two colorless aqueous solutions. One of the solutions contained Na2CO3 as the solute, and the other contained HCl. The chemical reaction that took place is represented by the equation above. What experimental result would be evidence that a chemical reaction took place when the solutions were combined? A Bubbles formed when the two solutions were combined. B The total volume of the mixture is close to the sum of the initial volumes. C The resulting solution is colorless. D The resulting solution conducts electricity.

A Bubbles formed when the two solutions were combined.

Based on the Brønsted-Lowry theory of acids and bases, which of the following species can act as both a conjugate acid and a conjugate base? A HS− B CH3COO− C H3O+ D NH4+

A HS−

2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s) Which of the following statements about the reaction represented above is correct? A It is an oxidation-reduction reaction, and Mg is oxidized. B It is an oxidation-reduction reaction, and electrons are transferred from SiCl4 to Mg C It is an oxidation-reduction reaction, and the oxidation number of Cl changes from +4 to +2. D It is not an oxidation-reduction reaction because none of the oxidation numbers change.

A It is an oxidation-reduction reaction, and Mg is oxidized.

HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l) A student carried out a titration using HC2H3O2(aq) and NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq) was added from a buret to the HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL of NaOH(aq), and what is the reason for this result? A It is less because more HC2H3O2(aq) reacted with the base. B It is the same because the equivalence point has not been reached. C It is the same because all of the coefficients in the neutralization equation are 1. D It is greater because HC2H3O2(aq) is a proton donor.

A It is less because more HC2H3O2(aq) reacted with the base.

A student was given two clear liquids; a colorless liquid and a dark-blue liquid. The student was asked to combine the liquids in a beaker and record observations. Which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined? A The resulting mixture was cloudy. B The total volume of the mixture was equal to the sum of the initial volumes. C The resulting liquid was light blue. D The liquids formed two separate layers in the beaker.

A The resulting mixture was cloudy.

Which of the following best explains what happens as photons of visible light are absorbed by dye molecules? A. Certain electrons in the dye molecule move to a higher energy level, with the difference in energy between the lower and higher energy levels being the same as the energy of the absorbed photons. B. Certain chemical bonds in the dye molecules begin to bend and stretch, with the difference in energy between the lower and higher vibrational states being the same as the energy of the absorbed photons. C. The dye molecules begin to rotate faster in certain modes, with the difference in energy between the lower and higher rotational states being the same as the energy of the absorbed photons. D. Certain covalent bonds in the dye molecules begin to break and re-form, with the bond energies of the bonds being the same as the energy of the absorbed photons.

A. Certain electrons in the dye molecule move to a higher energy level, with the difference in energy between the lower and higher energy levels being the same as the energy of the absorbed photons.

Which of the diagrams on slide 42 best represents the interactions that are responsible for the relatively large solubility of KCl crystals in water, and why? A. Diagram 1, because strong ion-dipole interactions between KCl and water help to dissociate the solute. B. Diagram 1, because strong London dispersion forces between the K+ and Cl− ions and water replace the weak London dispersion forces between two water molecules. C. Diagram 2, because strong dipole-dipole forces between KCl and water help to separate the KCl units within the crystals. D. Diagram 2, because the hydrogen bonds between water molecules expand to accommodate the KCl particles and pull them into solution.

A. Diagram 1, because strong ion-dipole interactions between KCl and water help to dissociate the solute.

Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region? A. Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states. B. Microwave photons cause electrons in the molecules to increase their electronic energy states, whereas infrared photons cause the molecules to increase their rotational energy states. C. Microwave photons cause the molecules to increase their vibrational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states. D. Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states.

A. Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states.

Which of the following best helps explain why the pressure of a sample of CH4(g) (molar mass 16g/mol) is closer to the pressure predicted by the ideal gas law than a sample of NH3(g)(molar mass 17g/mol) ? A. NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force. B. NH3 molecules have a greater molar mass than CH4 molecules, so the NH3 molecules collide with the walls of the container with more force. C. CH4 molecules have more hydrogen atoms than NH3 molecules, so CH4 molecules have more hydrogen bonding and greater intermolecular forces. D. CH4 molecules are larger than NH3 molecules, so the actual CH4 molecules take up a significant portion of the volume of the gas.

A. NH3 molecules are polar while CH4 molecules are not, and the greater attractions between NH3 molecules cause the molecules to collide with the walls of the container with less force.

The infrared spectrum on slide 43 represents the absorption of certain wavelengths of radiation by molecules of CO2. Which of the following best explains what occurs at the molecular level as the CO2 molecules absorb photons of the infrared radiation? A. The atoms in the CO2 molecules increase their vibration as the bonds between the atoms bend and stretch. B. The molecules of CO2 increase the energy of their rotational motions. C. The electrons in the valence shells of the atoms in the CO2 molecules are promoted to higher electronic energy levels. D. The bonds between the atoms in the CO2 molecules are continuously broken and then re-form.

A. The atoms in the CO2 molecules increase their vibration as the bonds between the atoms bend and stretch.

A student adds a 1g sample of an unknown, brittle solid to distilled water, stirs the mixture, and then measures its conductivity. The student repeats this procedure with more samples of the unknown solid and then produces the graph on slide 41. Which of the following statements about the graph and the properties of the solid is correct? A. The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water. B. The increase in conductivity indicates that the unknown is a network covalent solid that ionizes in water. C. The straight line plot indicates that the unknown solid is infinitely soluble in water. D. The straight line plot indicates that the unknown solid has a very low solubility in water.

A. The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water.

A student uses a spectrophotometer to analyze a solution of blue food dye. The student first rinses a cuvette with distilled water. Then the student adds the blue dye solution to the cuvette, forgetting to rinse the cuvette with the blue dye solution first. The student places the cuvette in the spectrophotometer and measures the absorbance of the solution. Assuming that some distilled water droplets were still in the cuvette when the blue dye solution was added, how would the measured absorbance be affected? A. The measured absorbance would be too low, because the distilled water left in the cuvette would slightly dilute the solution. B. The measured absorbance would be too low, because the distilled water would change the optimum wavelength of absorbance. C. The measured absorbance would be too high, because the water would allow more light to pass through the cuvette. D. The measured absorbance would be too high, because the distilled water would also absorb some light.

A. The measured absorbance would be too low, because the distilled water left in the cuvette would slightly dilute the solution.

Ar(g) deviates more from ideal behavior at extremely high pressures than Ne(g) does. Which of the following is one reason for this difference? A. The particle volume of Ar is greater than that of Ne. B. Ar atoms have more valence electrons than Ne atoms have, so Ar atoms have greater interparticle forces. C. The intermolecular forces between Ne atoms are greater than those between Ar atoms. D. Ar atoms are more attracted to the walls of the container than Ne atoms are.

A. The particle volume of Ar is greater than that of Ne.

The absorption spectrum of a certain red dye is shown above. If a student analyzing the same concentration of this dye neglected to wipe fingerprints off the cuvette before placing it in the spectrophotometer, how would the absorption curve be affected? A. The peak of the curve would be higher because more light would be absorbed. B. The peak of curve would be lower because less light would be absorbed. C. The peak of the curve would be shifted to the left because less light would be absorbed. D. The peak of the curve would be shifted to the right because more light would be absorbed.

A. The peak of the curve would be higher because more light would be absorbed.

Two sealed, rigid 5.0L containers each contain a gas at the same temperature but at a different pressure, as shown on slide 33. Also shown are the results of transferring the entire contents of container 1 to container 2. No gases escape during the transfer. Assuming ideal behavior, which statement is correct regarding the total pressure of the gases after they are combined? A. The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant. B. The total pressure of the gases in the mixture is lower than the sum of the initial pressures of oxygen and nitrogen because some of the energy of the particles will be lost due to an increase in the number of collisions. C. The total pressure of the gases in the mixture is higher than the sum of the initial pressures of oxygen and nitrogen because of the intermolecular forces that develop between oxygen and nitrogen molecules. D. The total pressure of the gases in the mixture cannot be determined because the actual value of the temperature is not given.

A. The total pressure of the gases in the mixture is the sum of the initial pressures of oxygen gas and nitrogen gas because pressure only depends on the total amount of gas when volume and temperature are held constant.

Compound J on slide 34 has two nitrogen atoms labeled x and y. A. Determine the hybridization of the nitrogen labeled y. B. A student claims that all the atoms in the molecule exist in a single plane. Do you agree with the student's claim? Justify your answer.

A. sp2 B. Disagree, N x is sp3 hybridized and it has a tetrahedral electron geometry. The hydrogen bonded to nitrogen x does not lie in the same plane as the rest of the atoms.

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? C2H3O2-(aq) + H3O+(aq) ---> HC2H3O2(aq) + H2O(l)

Acid-Base

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? NH3(aq) + HCl(aq) ---> NH4+(aq) + Cl-(aq)

Acid-Base

C6H5COOH(aq)+NaOH(aq)→C6H5COONa(aq)+H2O(l) What are the conjugate acid-base pair in the reaction represented above?

Acid: C5H5COOH Conjugate Base: C6H5COO-

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. What is the balanced net ionic equation for the formation of the precipitate?

Ag+(aq)+Cl−(aq)→AgCl(s)

The color of AgI(s), a salt of silver, is yellow. A student adds a solution of Nal to a test tube containing a small amount of solid, cream-colored AgBr. After stirring the contents of the test tube, the student observes that the solid in the test tube changes color from cream to yellow. Write the net ionic equation for the reaction that occurred in the test tube.

AgBr(s) + I-(aq) ---> AgI(s) + Br-(aq)

Which compound has the highest melting point: NaCl, CaCl2, Al2O3, Na2S, AlCl3?

Al2O3

Identify the element whose complete photoelectron spectrum is shown on slide 2. On the spectrum, draw a peak representing the 1s electrons of an element with one additional proton in the nucleus.

Aluminum (Al); the peak should be slightly to the left of the original 1s peak.

Ionic Compounds vs Molecular Compounds Empirical Formulas

An ionic compound's chemical formula is its empirical formula while molecular compounds can be simplified so the chemical formula is not always the same as the empirical formula.

Slide 11: Which of the following best describes the process represented above that takes place when NH3 is added to water? A It is a single replacement reaction in which an electron pair on N is replaced with an H atom. B It is an acid-base reaction in which a proton is exchanged from H2O to NH3. C It is a precipitation reaction in which NH4OH, an insoluble solid, is produced. D It is an oxidation-reduction reaction in which the oxidation number of N changes from −3 to −4.

B It is an acid-base reaction in which a proton is exchanged from H2O to NH3.

A student places a sample of a pure metal in a crucible and heats it strongly in air. The mass of the empty crucible is 12.0g. The mass of the crucible and sample before heating was 14.4g. The mass of crucible and sample after heating was 16.0g. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct? A The mass of the sample decreased, so physical changes occurred as the metal first melted and then boiled out of the crucible. B The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance. C There was nothing for the metal to react with, so only a physical change could have occurred. D The sample was only heated, so neither a physical nor a chemical change occurred.

B The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.

HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place? A The resulting solution is colorless. B The temperature of the reaction mixture increases. C The total volume of the mixture is approximately equal to the sum of the initial volumes. D The resulting solution conducts electricity.

B The temperature of the reaction mixture increases.

At 10.°C, 20.g of oxygen gas exerts a pressure of 2.1atm in a rigid, 7.0L cylinder. Assuming ideal behavior, if the temperature of the gas was raised to 40.°C, which statement indicates the new pressure and explains why? A. 1.9atm, because the pressure P decreases by the proportion 283/313. B. 2.3atm, because the pressure P increases by the proportion 313/283. C. 0.52atm, because the pressure P decreases by the proportion 10/40. D. 8.4atm, because the pressure P increases by the proportion 40/10.

B. 2.3atm, because the pressure P increases by the proportion 313/283.

A gaseous air‑fuel mixture in a sealed car engine cylinder has an initial volume of 600.mL at 1.0atm. To prepare for ignition of the fuel, a piston moves within the cylinder, reducing the volume of the air‑fuel mixture to 50.mL at constant temperature. Assuming ideal behavior, what is the new pressure of the air‑fuel mixture? A. About 0.083atm, because the initial volume of the gas mixture was 12 times larger than its final volume. B. About 12atm, because the volume of the gas mixture decreased by a factor of 12. C. About 120.atm, because the initial volume of the gas mixture was 120 times larger than its final volume. D. About 550.atm, because the change in the volume of the gas mixture was 550.mL.

B. About 12atm, because the volume of the gas mixture decreased by a factor of 12.

The diagrams on slide 30 represent two allotropes of solid phosphorus. Which of the following correctly identifies the allotrope with the higher melting point and explains why? A. Allotrope I, because it has P4 molecules with covalent bonds that are stronger than dispersion forces between individual P atoms in allotrope II. B. Allotrope II, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4 molecules in allotrope I. C. Allotrope II, because it has metallic bonding that is stronger than the covalent bonding found in the P4 molecules in allotrope I. D. Both allotropes have the same melting point because they both contain phosphorous atoms.

B. Allotrope II, because it has covalent bonds between the phosphorous atoms that are stronger than the dispersion forces between the P4 molecules in allotrope I.

The structure of one form of boron nitride is represented on slide 15. This form of boron nitride is one of the hardest substances known. Which of the following best helps explain why boron nitride is so hard? A. Boron ions and nitrogen ions are held together by ionic bonds. B. Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles. C. Boron nitride is an alloy, and alloys are typically harder than the elements used to make them. D. Boron nitride is a polymer made of long chains of boron atoms and nitrogen atoms held together by dispersion forces.

B. Boron nitride is a network solid of atoms connected by covalent bonds with fixed bond angles.

Equimolar samples of CH4(g) and C2H6(g) are in identical containers at the same temperature. The C2H6(g) deviates much more from ideal behavior than the CH4(g) does. Which of the following best helps explain this deviation? A. C2H6 molecules have more hydrogen bonding than CH4 molecules do. B. C2H6 molecules have a larger, more polarizable electron cloud than CH4 molecules do. C. The C2H6 molecules have a greater average kinetic energy than the CH4 molecules have. D. The C2H6 molecules have a greater average speed than the CH4 molecules have.

B. C2H6 molecules have a larger, more polarizable electron cloud than CH4 molecules do.

The diagram on slide 20 shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table, which of the following would be the best way to decrease the distance that the products travel up the plate? A. Use pentane instead of hexane in the solvent. B. Decrease the percentage of ethyl acetate in the solvent. C. Increase the percentage of ethyl acetate in the solvent. D. Add up to 5% methanol to the solvent.

B. Decrease the percentage of ethyl acetate in the solvent.

The ionic compounds NaCl and MgS are represented by the diagrams on slide 14. Which statement correctly identifies diagram 1 and identifies the compound with the lower melting point, explaining why? A. Diagram 1 represents NaCl; it has a lower melting point than MgS has because the coulombic attractions between the singly charged Na+ ions and the Cl− ions in NaCl are stronger than those between the ions in MgS. B. Diagram 1 represents NaCl; it has a lower melting point than MgS because the coulombic attractions between its singly charged Na+ ions and the Cl− ions are weaker than those between the ions in MgS. C. Diagram 1 represents MgS; it has a lower melting point than NaCl because the coulombic attractions between its doubly charged Mg2+ ions and the S2− ions are stronger than those between the ions in NaCl. D. Diagram 1 represents MgS; it has a lower melting point than NaCl because the coulombic attractions between the doubly charged Mg2+ ions and the S2− ions are weaker than those between the ions in NaCl.

B. Diagram 1 represents NaCl; it has a lower melting point than MgS because the coulombic attractions between its singly charged Na+ ions and the Cl− ions are weaker than those between the ions in MgS.

A student places a piece of I2(s) in 50.0 mL of H2O(l), another piece of I2(s) of the same mass in 50.0 mL of C6H14(l), and shakes the mixtures. The results are shown above. What do the results indicate about the intermolecular interactions of the substances? A. I2 and H2O have similar intermolecular interactions, and I2 and C6H14 do not. B. I2 and C6H14 have similar intermolecular interactions, and I2 and H2O do not. C. I2, H2O, and C6H14 all have similar intermolecular interactions. D. I2, H2O, and C6H14 have three completely different types of intermolecular interactions.

B. I2 and C6H14 have similar intermolecular interactions, and I2 and H2O do not.

The diagram on slide 28 represents four cations, all shown to the same scale. Which cation would be predicted by Coulomb's law to have the strongest ion-dipole attraction to water, and why? A. Li+, because it is the smallest group 1 metal ion. B. Mg2+, because it has the largest charge-to-size ratio. C. Na+, because it has the smallest charge-to-size ratio. D. Ca2+, because it is the largest group 2 metal ion.

B. Mg2+, because it has the largest charge-to-size ratio.

One type of organic molecule can be converted to another type of organic molecule through an oxidation-reduction process, as represented in the diagram on slide 44. Which of the following best explains why infrared spectroscopy is an appropriate method to confirm that the product contains a carbonyl? A. The absorption of infrared radiation causes the nonbonding electrons on oxygen to transition into a higher electronic energy level. B. The absorption of infrared radiation leads to an increase in molecular vibrational level associated with the stretching of the carbonyl. C. The absorption of infrared radiation causes the electrons in the pi bond to transition to a higher bonding energy level. D. Infrared radiation leads to an increase in the molecular rotational level associated with the carbonyl as the axis of rotation.

B. The absorption of infrared radiation leads to an increase in molecular vibrational level associated with the stretching of the carbonyl.

Infrared spectroscopy is a useful tool for scientists who want to investigate the structure of certain molecules. Which of the following best explains what can occur as the result of a molecule absorbing a photon of infrared radiation? A. The energies of infrared photons are in the same range as the energies associated with changes between different electronic energy states in atoms and molecules. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the energies of electronic transitions within the molecules. B. The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the types and strengths of different bonds in the molecules. C. The energies of infrared photons are in the same range as the energies associated with different rotational states of molecules. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the energies of transition between different rotational energy states of the molecules. D. The energies of infrared photons are in the same range as the total bond energies of bonds within molecules. Chemical bonds can be completely broken as they absorb infrared photons of characteristic wavelengths, thus revealing the energies of the bonds within the molecules.

B. The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the types and strengths of different bonds in the molecules.

The diagrams on slide 19 represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why? A. The gas in sample 1 would deviate more from ideal behavior because the average distance an Xe atom travels before colliding with another Xe atom is greater. B. The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions. C. The gas in sample 2 would deviate more from ideal behavior because the average speed of the Xe atoms is less, leading to an increase in intermolecular attractions. D. The gases in both sample 1 and sample 2 would show the same deviation from ideal behavior.

B. The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions.

A student measures the absorbance of a solution containing FeSCN2+ ions using a spectrophotometer. The cuvette used by the student has two frosted walls and two transparent walls. The student properly orients the cuvette so that the path of the light goes through the transparent sides of the cuvette when calibrating the spectrophotometer. How will the measured absorbance of the FeSCN2+ be affected if the student incorrectly orients the cuvette so that the path of the light is through the frosted sides of the cuvette? A. The measured absorbance of the FeSCN2+ solution will not be affected. B. The measured absorbance of the FeSCN2+ solution will be higher than the actual absorbance. C. The measured absorbance of the FeSCN2+ solution will be lower than the actual absorbance. D. The effect on the measured absorbance of the FeSCN2+ solution depends on the concentration of the FeSCN2+ solution.

B. The measured absorbance of the FeSCN2+ solution will be higher than the actual absorbance.

Four electron domains molecules with 2 lone pairs

Bent molecules; 104.5*

Why does KBr (672 kJ/mol) have a higher lattice energy than KI (623 kJ/mol)?

Bromide ions have a smaller ionic radius than iodide ions. This results in a smaller distance btw the potassium ion and the bromide ion. The smaller distance increases the coulombic attraction resulting in higher lattice energy.

Methanol, CH3OH, dissolves completely in water to form a solution that does not conduct electricity. Which of the diagrams on slide 40 best shows the major type of attractive force that exists between the particles in the solution?

The diagram on slide 36 shows the distribution of speeds for a sample of O2(g). Which of the graphs shows the distribution of speeds for the same sample at a higher temperature (dashed line) ?

Which of the particulate diagrams on slide 2 best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125*C?

Mass of NaI crystals: 2.0 g Color of NaI crystals: white Color of solid recovered: yellow Color of filtered solution: colorless Mass of dry solid recovered: 3.0g When students added 2.0g of NaI crystals to 100.mL of Pb(NO3)2(aq), a yellow precipitate formed. After the solution was filtered, the yellow solid was dried and weighed. Data from the experiment are shown in the table above. Which of the following claims is best supported by the observations? A A physical change occurred when a new yellow compound was formed. B A physical change occurred when the color of the NaI solid added changed to yellow when mixed with water. C A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed. D A chemical change occurred when covalent bonds between the yellow solid and water were broken during drying.

C A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed.

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration? A Two colorless solutions were combined, and the resulting solution was pink. B When a solid was added to a liquid, sparks were produced. C One piece of solid substance was changed into small pieces. D When two solutions were combined, a precipitate formed.

C One piece of solid substance was changed into small pieces.

A student combines a solution of NaCl(aq)NaCl(aq) with a solution of AgNO3(aq)AgNO3(aq), and a precipitate forms. Which of the following is evidence that ionic bonds formed during the precipitation? A The resulting solution is colorless. B The resulting solution conducts electricity. C The precipitate has a high melting point. D The temperature of the solution did not change significantly during the precipitation.

C The precipitate has a high melting point.

A student was asked to formulate a hypothesis about what would happen if 100.mL of 0.1MNaOH(aq) at 25°C was combined with 100.mL of 0.1MMgCl2(aq) at 25°C. Which of the following hypotheses indicates that the student thought a chemical change would occur? A The volume of the resulting solution will be equal to the sum of the volumes of the original solutions. B The mass of the resulting solution will be equal to the sum of the masses of the original solutions. C The resulting solution would contain a precipitate. D The resulting solution will be clear.

C The resulting solution would contain a precipitate.

K2SO3(aq)+2HNO3(aq)→2KNO3(aq)+SO2(g)+H2O(l) According to the balanced chemical equation above, when 100.0mL of 0.100MK2SO3(aq) is mixed with 100.0mL of 0.200MHNO3(aq) at 30°C and 1 atm, the volume of SO2 gas produced is 0.24 L. If it is assumed that the reaction goes to completion, which of the following changes would double the volume of SO2 produced at the same temperature and pressure, and why? (For each change, assume that the other solutions and volumes remain the same.) A Using 200.0mL of the 0.100MK2SO3(aq), because it then becomes the reactant in excess B Using 200.0mL of the 0.200MHNO3(aq), because the volume of SO2 produced is inversely proportional to the number of moles at constant temperature and pressure C Using 200.0mL of 0.100MK2SO3(aq) and 200.0mL of 0.200MHNO3(aq), because this provides double the number of moles with the correct stoichiometric ratio D Using 400.0mL of 0.100MK2SO3(aq) and 200.0mL of 0.200MHNO3(aq), because this provides the same number of moles of each reactant

C Using 200.0mL of 0.100MK2SO3(aq) and 200.0mL of 0.200MHNO3(aq), because this provides double the number of moles with the correct stoichiometric ratio

Put the following bonds in order of increasing polarity: C-H, C-F, C-O, Ca-C

C-C < C-H < C-O < C-F < Ca-C

The frequency and energy ranges of photons in some parts of the electromagnetic spectrum are given in the table on slide 45. Which of the following could be the energy of a photon in the visible range? A. 9×10−21J B. 4×10−20J C. 4×10−19J D. 9×10−19J

C. 4×10−19J

A gas mixture at 0°C and 1.0atm contains 0.010mol of H2, 0.015mol of O2, and 0.025mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture? A. About 0.010atm, because there is 0.010mol of H2 in the sample. B. About 0.050atm, because there is 0.050mol of gases at 0°C and 1.0atm1. C. About 0.20atm, because H2 comprises 20% of the total number of moles of gas. D. About 0.40atm, because the mole ratio of H2:O2:N2 is 0.4:0.6:1.

C. About 0.20atm, because H2 comprises 20% of the total number of moles of gas.

The structures of two allotropes of carbon are represented on slide 32. Which of the following statements best helps explain why diamond is much harder than graphite? A. Diamond contains covalent bonds, whereas graphite contains ionic bonds. B. Diamond contains ionic bonds, whereas graphite contains covalent bonds. C. Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces. D. Carbon atoms in diamond have a sea of mobile electrons that make the structure strong, whereas graphite does not contain delocalized electrons.

C. Carbon atoms in diamond have four covalent bonds, whereas graphite is made of layers that are held together by relatively weak dispersion forces.

Which particle diagram shown above best represents the strongest intermolecular force between two ethanol, C2H6O molecules on slide 27? A. Diagram 1, because it shows hydrogen bonds forming between hydrogen atoms from different ethanol molecules. B. Diagram 1, because it shows strong, directional dipole-dipole forces between two polar ethanol molecules. C. Diagram 2, because it shows the formation of a hydrogen bond between an H atom bonded to an O atom with an O atom from another molecule. D. Diagram 2, because it shows the dipole from an ethanol molecule inducing a dipole in another ethanol molecule.

C. Diagram 2, because it shows the formation of a hydrogen bond between an H atom bonded to an O atom with an O atom from another molecule.

The survival of aquatic organisms depends on the small amount of O2 that dissolves in H2O. The diagrams on slide 23 represent possible models to explain this phenomenon. Which diagram provides the better particle representation for the solubility of O2 in H2O, and why? A. Diagram 1, because O2 molecules can form hydrogen bonds with the H2O molecules. B. Diagram 1, because O2 and H2O are polar molecules that can interact through dipole-dipole forces. C. Diagram 2, because the polar H2Omolecules can induce temporary dipoles on the electron clouds of O2 molecules. D. Diagram 2, because the nonpolar O2 molecules can induce temporary dipoles on the electron clouds of H2O molecules.

C. Diagram 2, because the polar H2Omolecules can induce temporary dipoles on the electron clouds of O2 molecules.

The two gas samples represented in the graph on slide 35 are at the same temperature. Which of the following statements about the gases is correct? A. The molecules of gas Z have a higher average kinetic energy than the molecules of gas X. B. There are fewer molecules in the sample of gas Z than in the sample of gas X. C. Gas Z has a smaller molar mass than gas X. D. Gas Z has a greater molar mass than gas X.

C. Gas Z has a smaller molar mass than gas X.

Which statement best helps to explain the observation that NH3(l)NH3(l) boils at −28°C, whereas PH3(l) boils at −126°C? A. The dispersion forces in NH3 are weaker than the dispersion forces in PH3. B. The dispersion forces in NH3 are stronger than the dipole-dipole forces in PH3. C. NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3. D. NH3 has hydrogen bonding that is weaker than the dipole-dipole forces in PH3.

C. NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3.

Diagram 1 on slide 16 shows equimolar samples of two gases inside a container fitted with a removable barrier placed so that each gas occupies the same volume. The barrier is carefully removed as the temperature is held constant. Diagram 2 above shows the gases soon after the barrier is removed. Which statement describes the changes to the initial pressure of each gas and the final partial pressure of each gas in the mixture and also indicates the final total pressure? A. The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases. B. The partial pressure of each gas in the mixture is double its initial pressure; the final total pressure is twice the sum of the initial pressures of the two gases. C. The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases. D. The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is the same as the sum of the initial pressures of the two gases.

C. The partial pressure of each gas in the mixture is half its initial pressure; the final total pressure is half the sum of the initial pressures of the two gases.

A solid compound of a group 1 (alkali) metal and a group 17 (halogen) element dissolves in water. The diagram on slide 29 represents one type of solute particle present in the solution. Which of the following identifies the solute particle and best helps explain how the solute particle interacts with water molecules? A. The particle is a negative ion, and the interactions are hydrogen bonds. B. The particle is a negative ion, and the interactions are ion-dipole attractions. C. The particle is a positive ion, and the interactions are ion-dipole attractions. D. The particle is a positive ion, and the interactions are dipole-dipole attractions.

C. The particle is a positive ion, and the interactions are ion-dipole attractions.

Four different liquid compounds in flasks at 20°C are represented on slide 13. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane? A. The random motion of the particles within the liquids B. The relative speeds of the vapor particles in each flask C. The strength of the intermolecular forces between the particles in the liquids D. The structural formula of the molecules of the liquid and vapor in each flask

C. The strength of the intermolecular forces between the particles in the liquids

Beta-carotene is an organic compound with an orange color. The diagram on slide 25 shows the ultraviolet spectrum of beta-carotene. Which of the following statements is true about the absorption bands in the spectrum? A. The absorption band between 250 and 320 nm is due to transitions in electronic energy levels, and the absorption band between 380 and 520 nm is due to transitions in molecular vibrational levels. B. The absorption band between 250 and 320 nm is due to transitions in molecular vibrational levels, and the absorption band between 380 and 520 nm is due to transitions in molecular rotational levels. C. The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths. D. The two main absorption bands are associated with transitions in molecular vibrational levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.

C. The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.

Which of the following compounds has the highest percent by mass of carbon? CO, CO2, CH4, or C2H4

C2H4

A 23.0 g sample of a compound contains 12.0g C, 3.0g H, and 8.0g O. What is the empirical formula of the compound?

C2H6O

Which compound C2H6, C3H8, or C4H10 has the highest boiling point?

C4H10

What is the empirical formula of C2H4O2?

CH2O

A compound is 80% carbon and 20% hydrogen by mass. What is its empirical formula? If the same compound has a molar mass of 30. g/mol, what is its molecular formula?

CH3; C2H6

Which of the following compounds is expected to be most water soluble? C3H8, CH2O, CH3OH, of HCL

CH3OH

A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula of the compound?

Ca(OH)2

Classify Cl2, Ni, BN, and FeS as ionic molecular, covalent network, or metallic solids and arrange them in order of increasing melting points.

Cl2 (molecular), FeS (ionic), Ni (metallic), BN (covalent network)

Zn(s)+CuSO4(aq)→Cu(s)+ZnSO4(aq) When a zinc plate is placed in an aqueous solution of copper sulfate, elemental copper forms, as represented by the equation above. Which of the following represents the reduction half-reaction of the reaction?

Cu2+(aq)+2e−→Cu(s)

A student obtains a liquid sample of green food coloring that is known to contain a mixture of two solid pigments, one blue and one yellow, dissolved in an aqueous solution of ethanol. Which of the laboratory setups on slide 21 is most appropriate for the student to use in order to separate and collect a substantial sample of each of the two pigments?

A student performed a fractional distillation of a mixture of two straight-chain hydrocarbons, C7H16 and C8H18. Using four clean, dry flasks, the student collected the distillate over the volume ranges (A, B, C, and D) shown in the graph on slide 22. Over what volume range should the student collect the distillate of the compound with the stronger intermolecular forces?

The diagrams on slide 8 represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams on slide 9 is the best particle representation of the mixture after the precipitation reaction occurred?

A student mixes 20.0g of white KCl crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred? A The solution does not change color after stirring. B The KCl crystals are no longer visible after mixing with water. C There is a temperature change in the solution during the dissolving process. D After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

D After the water has evaporated, the white crystals in the beaker have a mass of 20.0g.

A beaker was half filled with freshly distilled H2O and placed on a hot plate. As the temperature of the water reached 100°C, vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of which of the following substances would support the claim that the observed phenomenon was a physical change? A H2(g) B O2(g) C CO2(g) D H2O(g)

D H2O(g)

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) When the reaction represented above proceeds, heat is produced. Which of the following best describes the reaction? A It is a combustion reaction because heat is produced by the reaction. B It is a double replacement reaction because 2Cl atoms are added to Zn. C It is an acid-base reaction because HCl is an acid that is capable of exchanging H+. D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.

D It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.

The table on slide 7 summarizes data given to a student to evaluate the type of change that took place when substance X was mixed with water. The student claimed that the data did not provide enough evidence to determine whether a chemical or physical change took place and that additional tests were needed. Which of the following identifies the best way to gather evidence to support the type of change that occurred when water and X were mixed? A Measuring the melting point of the mixture of water and X B Adding another substance to the mixture of water and X to see whether a solid forms C Measuring and comparing the masses of the water, X, and the mixture of water and X D Measuring the electrical conductivities of X and the mixture of water and X

D Measuring the electrical conductivities of X and the mixture of water and X

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Assume that 50.0mL of 1.0MNaCl(aq) and 50.0mL of 1.0MAgNO3(aq) were combined. According to the balanced equation, if 50.0mL of 2.0MNaCl(aq) and 50.0mL of 1.0MAgNO3(aq) were combined, the amount of precipitate formed would A double, because all of the coefficients are 1 B double, because the amount of one of the reactants was doubled C not change, because all of the coefficients are 1 D not change, because the amount of AgNO3(aq) did not change

D not change, because the amount of AgNO3(aq) did not change

An equimolar mixture of N2(g) and Ar(g) is kept inside a rigid container at a constant temperature of 300 K. The initial partial pressure of Ar in the mixture is 0.75atm. An additional amount of Ar was added to the container, enough to double the number of moles of Ar gas in the mixture. Assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the Ar gas? A. 0.75atm, because increasing the partial pressure of Ar decreases the partial pressure of N2. B. 1.13atm, because 33% of the moles of gas are N2. C. 1.50atm, because the number of moles of N2 did not change. D. 2.25atm, because doubling the number of moles of Ar doubles its partial pressure.

D. 2.25atm, because doubling the number of moles of Ar doubles its partial pressure.

The gasesCO2(g) and NH3(g) can be liquefied at 20°C by compressing them to sufficiently high pressures. A student claims that )=NH3(g) can be liquefied at a lower pressure than CO2(g) can be liquefied. Which of the following is the best justification for this claim? A. At 20°C, the average speed of NH3 molecules is greater than that of CO2 molecules because NH3 molecules have less mass than CO2 molecules have. B. CO2 is a nonpolar molecule that has no significant intermolecular forces, whereas NH3 has strong London dispersion intermolecular forces. C. Both CO2 and NH3 are nonpolar molecules that have only London dispersion intermolecular forces, but the larger electron cloud of CO2 molecules causes it to have stronger intermolecular forces. D. CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3 molecules.

D. CO2 is a nonpolar molecule that has London dispersion intermolecular forces that are weaker than the dipole-dipole and London dispersion forces between the polar NH3 molecules.

The crystal structure of NaBr is represented in the diagram on slide 31. Which statement correctly compares crystalline NaBr(s) to molten NaBr(l) in terms of electrical conductivity? A. Crystalline NaBr contains no freely moving electrons that could conduct an electrical current, whereas electrons can flow freely in molten NaBr, which is a good conductor of electricity. B. Crystalline NaBrand molten NaBr both contain ions that are held in fixed positions due to strong electrostatic attractions among the ions, making neither a good electrical conductor. C. Crystalline NaBr and molten NaBr both contain Na atoms that transfer electrons to Br atoms in a chemical reaction, thus allowing them both to be good conductors of electricity. D. Crystalline NaBr contains no freely moving electrons to conduct electricity, but molten NaBr is composed of freely moving Na+ and Br− ions, which allows it to be a good conductor of electricity.

D. Crystalline NaBr contains no freely moving electrons to conduct electricity, but molten NaBr is composed of freely moving Na+ and Br− ions, which allows it to be a good conductor of electricity.

The diagrams on slide 34 use arrows to represent the speed of a gas particle. Which of the diagrams best represents the speed of the particles of a gas at a fixed temperature, and why? A. Diagram 1, because all the particles have the same speed. B. Diagram 1, because the particles are moving in different directions. C. Diagram 2, because the particles have a net kinetic energy of zero. D. Diagram 2, because the particles have a variety of different speeds.

D. Diagram 2, because the particles have a variety of different speeds.

The diagram on slide 11 is a molecular model of a gaseous diatomic element that is just above its boiling point. Intermolecular forces between the gas molecules will cause them to condense into the liquid phase if the temperature is lowered. Which of the following best describes how the model is limited in its depiction of the phenomenon? A. It does not show how hydrogen bonds are constantly forming, breaking, and reforming, which results in a net force of attraction between the molecules. B. It does not show how the interactions between ions and the induced molecular dipoles result in a net force of attraction between the molecules. C. It does not show how the interacting permanent dipoles of the molecules result in a net force of attraction between the molecules. D. It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.

D. It does not show how the temporary fluctuating dipoles of the molecular electron clouds result in a net force of attraction between the molecules.

Slide 12: The electron cloud of HF is smaller than that of F2, however, HF has a much higher boiling point than F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HF? A. F2F2 is soluble in water, whereas HFHF is insoluble in water. B. The F2F2 molecule has a greater mass than the HFHF molecule has. C. Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has strong ionic interactions between H+H+ and F−F− ions. D. Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

D. Liquid F2F2 has weak dispersion force attractions between its molecules, whereas liquid HFHF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

Which of the following methods is most appropriate to use to determine the number of different-colored components in a sample of black ink? A. Distillation at atmospheric pressure B. Elemental analysis to determine the mass ratio of C:H:N:O C. Column chromatography using a nonpolar stationary phase and water as the mobile phase D. Paper chromatography using different solvents with a range of polarities as the mobile phase

D. Paper chromatography using different solvents with a range of polarities as the mobile phase

The graph on slide 37 shows how a particular real gas deviates from ideal behavior at very high pressures. Based on this information, which of the following is most likely the gas and gives the reason based on kinetic molecular theory? A. H2, because it has the smallest mass. B. N2, because its molecules have a triple bond. C. Ne, because it has a completely filled valence shell. D. SO2, because it has the largest molecular volume.

D. SO2, because it has the largest molecular volume.

A 1L sample of helium gas at 25°C and 1atm is combined with a 1L sample of neon gas at 25°C and 1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct? A. The average speed of the helium atoms increases when the gases are combined. B. The average speed of the neon atoms increases when the gases are combined. C. The average kinetic energy of the helium atoms increases when the gases are combined. D. The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

D. The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.

The graph on slide 18 shows the distribution of molecular speeds for four different gases at the same temperature. What property of the different gases can be correctly ranked using information from the graph, and why? A. The densities of the gases, because as the density of a gas increases, the average speed of its molecules decreases. B. The pressures of the gases, because the pressure exerted by a gas depends on the average speed with which its molecules are moving. C. The volumes of the gases, because at a fixed temperature the volume of a gas can be calculated using the equation PV=nRT. D. The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass can be calculated using the equation KEavg=12mv^2.

D. The molecular masses of the gases, because the gas molecules have the same average kinetic energy and mass can be calculated using the equation KEavg=12mv^2.

Two possible Lewis diagrams for cyanic acid as well as experimentally determined information about cyanic acid is presented on slide 22. Choose which diagram best agrees with the experimental data presented. Justify your answer using VSEPR theory.

Diagram 1--There are 4 electron domains around the oxygen atom, making its geometry tetrahedral with a bond angle around 109.5*.

When methanol and water are mixed together, they form a homogeneous mixture. Based on the information in the table on slide 38, which method would be the best procedure for separating a mixture of methanol and water?

Distillation

The diagram on slide 5 represents H2(g) and N2(g) in a closed container. Which of the diagrams on slide 5 would represent the results if the reaction shown were to proceed as far as possible? N2(g) + 2H2(g) ---> 2NH2(g)

Which solvent would be most effective dissolving the following solutes, hexane (C6H14) or water? Identify the dominant type of intermolecular force present between solute and solvent particles and draw a particulate drawing showing where these interactions occur. Ethanol (C2H5OH)

Ethanol is part hydrocarbon (nonpolar) and part polar at the -OH hydroxyl group. Since the hydrocarbon portion is relatively small, the very polar -0H group will dominate. Ethanol can form hydrogen bonds with water and is therefore more miscible in water. See slide 3

Choose the atom with the higher electronegativity: F or O

Choose the atom with the higher first ionization energy: F and O

Which of the elements Li, Be, C, F, Na, Mg, Si, or Cl has the highest ionization energy?

Which gas out of the following is most ideal: CO2, NH3, or F2?

A mixture of metals is made up of 1.00 g each of Cu, Fe, and Sn. The sample contains the most atoms of which metal?

5Fe2+(aq)+MnO4−(aq)+8H+(aq)→5Fe3+(aq)+Mn2+(aq)+4H2O(l) Which of the following represents the oxidation half-reaction based on the balanced ionic equation shown above?

Fe2+(aq)→Fe3+(aq)+e−

Which substance would have the greatest (most exothermic) lattice energy? FeCl2 vs FeCl3

FeCl3

Based on the following ionization energies, what group does the element most likely come from? IE1 = 577 kJ/mol, IE2 = 1816 kJ/mol, IE3 = 2881 kJ/mol, IE4 = 11,600 kJ/mol

Group 13

Given a sample of H2, HCl, and Cl2 at the same temperature, place the particles in order of decreasing average particle speed.

H2, HCl, Cl2

Consider an equimolar mixture of gases, H2, N2 and F2, placed into container with a pinhole opening. After some time has passed, place the gases in order of increasing amount remaining in the container.

H2, N2, F2

Which compound HCl, H2O, or PH3 has the highest boiling point?

H2O

HNO3(aq) + H2O(l) ---> NO3-(aq) + H3O+(aq) For the dissolution of HNO3 in water represented above, which species are Bronsted-Lowry bases?

H2O(l) and NO3-(aq)

What are the strong acids?

HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4

What is the correct net ionic equation of the neutralization reaction between hydrofluoric acid and sodium hydroxide in aqueous solution?

HF(aq) + OH-(aq) --> H2O(l) + F-(aq)

Write a net ionic equation for the reaction: HNO2 (aq) + KOH (aq) ---> ???

HNO2 (aq) + OH(-1)(aq) ---> H2O(l) + NO2(-1)(aq)

HNO3(aq) + H2O(l) ---> NO3-(aq) + H3O+(aq) For the dissolution of HNO3 in water represented above, which species are Bronsted-Lowry acids?

HNO3(aq) and H3O+(aq)

HNO3(aq) + H2O(l) ---> NO3-(aq) + H3O+(aq) For the dissolution of HNO3 in water represented above, what are the two sets of conjugate acid-base pairs?

HNO3(aq) and NO3-(aq) are a conjugate acid-base pair and H2O(l) and H3O+(aq) are a conjugate acid-base pair

HNO3(aq) + H2O(l) ---> NO3-(aq) + H3O+(aq) For the dissolution of HNO3 in water represented above, what occurs during the reaction that identifies it as an acid-base reaction?

HNO3(aq) donates a proton and becomes NO3-(aq) and H2O(l) accepts a proton and becomes H3O+(aq)

What is the empirical formula of H2O2?

A student is carrying out various experiments in a lab. In one experiment, the student mixes two clear, colorless solutions together, and a yellow precipitate is formed. The student determines that this is evidence of a chemical reaction. Do you agree with the student? Justify your answer.

I agree with the student. This is an example of a chemical reaction because a precipitate is formed. We can conclude that a new product was made after the solutions were mixed that has different chemical properties than the original solutions.

What type of solid is I2(s) an example of?

I2 (s)

The diagram on slide 8 shows two resonance structures for a molecule of C6H6. The phenomenon shown in the diagram best supports what claim about the bonding in C6H6C6H6 ?

In the C6H6 molecule, all the bonds between the carbon atoms have the same length.

What type of spectroscopy would be responsible for the bending of the O-H bonds in water?

Infrared Vibrational Spectroscopy

What kind of substance is NaF?

Ionic

What kind of substance is ZnCl2?

Ionic

Two pure elements react to form a compound. One element is an alkali metal, X, and the other element is a halogen, Z. What scientific claim can be made about the compound?

It contains ionic bonds

KCl is an ionic compound. The strong charges on K+ and Cl- would attract strongly to the polar partial charges in water and form ion-dipole interactions. KCl is miscible in water. See slide 4

What is the empirical formula of a compound that is 28.7% K, 1.5% H, 22.8% P, and 47.0% O?

KH2PO4

Choose the atom with the higher electronegativity: Na or Li

Choose the atom with the higher first ionization energy: Na or Li

What are the strong bases?

LiOH, NaOH, KOH, RbOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

Two electron domain molecules

Linear Molecules; 180.0 *

sp hybridization

Linear; 180*

What kind of substance is CuZn?

Metallic

Which substance would have the greatest (most exothermic) lattice energy? MgO vs BaO

MgO

Which substance would have the greatest (most exothermic) lattice energy? MgO vs NaCl

MgO

NH3(aq) + HCl(aq) <--- ---> NH4+(aq) + Cl-(aq) What are the Bronsted-Lowry bases in the reaction represented above?

NH3(aq) and Cl-(aq)

What is the correct net ionic equation of the reaction that occurs when aqueous solutions of ammonia and hydrochloric acid are combined?

NH3(aq)+H+(aq)→NH4+(aq)

Choose the atom with the larger atomic radius: Na or Li

Which of the elements Li, Be, C, F, Na, Mg, Si, or Cl has the largest atomic radius?

What is the empirical formula of Na2SO4?

Na2SO4

Calcium reacts with a certain element to from a compound with a general formula CaX2. What would be the most likely formula for a compound formed btw sodium and element X?

NaX

A student claims that a compound with sodium and fluorine and a compound with sodium and oxygen will have the same formula. Do you agree? Why or why not?

No, I disagree. Sodium ion has a charge of 1+, fluoride has a charge of 1- and oxide a charge of 2-. The formula when Na and F bond will be NaF. Sodium and oxygen will form Na2O.

A student claims that F2 is more polar than H2 because fluorine has a higher electronegativity than hydrogen. Do you agree with this claim? Explain why or why not? (The electronegativities of hydrogen and fluorine are 2.1 and 4.0 respectively.)

No, because polarity is the distance in electroneg. not the absolute value of the electroneg.. Fluorine and hydrogen have the same difference in elecroneg. (0), so they have the same polarity.

Polar or nonpolar? slide 23

Nonpolar

What kind of substance is Al?

Nonpolar Covalent

What kind of substance is CH4?

Nonpolar covalent

What kind of substance is H2?

Nonpolar covalent

Choose the atom with the larger atomic radius: F or O

What is the oxidation number for Cl in Cl2 (g)?

0.0064 g of a diatomic gas occupies a volume of 44.8 mL at STP. What is the identity of the gas?

CH4 (g) + 2 O2 (g) ---> CO2 (g) + 2 H2O (g) If 32 g of CH4 are mixed with 32 g of O2, what is the limiting reactant? How many grams of water will be produced? How many grams of excess reactant remain?

O2, 18.016 g H2O, 24.063 g CH4

Cu(s)+2AgNO3(aq)→Cu(NO3)2(aq)+2Ag(s) The reaction between solid copper and aqueous silver nitrate produces solid silver and a blue solution, as represented by the balanced equation shown above. Based on the balanced equation, what are the oxidation and reduction half-reactions?

Oxidation Half-reaction: Cu(s) ---> Cu(2+)(aq) + 2e- Reduction Half-reaction: Ag+(aq) + e- ---> Ag(s)

I2(aq)+C6H8O6(aq)→C6H6O6(aq)+2I−(aq)+2H+(aq) The compound C6H8O6 reacts with I2 according to the reaction represented by the equation above. What type of reaction is this?

Oxidation-reduction

Slide 10: When C2H4(g) reacts with H2(g), the compound C2H6(g) is produced, as represented by the equation above. What type of reaction is this?

Oxidation-reduction

Which element has the smallest atomic radius: nitrogen, oxygen, or sulfur?

Oxygen

A compound is determined to be 43.6% P and the remainder oxygen. What is the empirical formula of the compound?

P2O5

Equal volumes of 0.2M solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. What is the net ionic equation for the reaction?

Pb2+(aq)+2Br−(aq)→PbBr2(s)

The electronegativity of P is 2.3 and Cl is 3.0. On which element is the partial positive charge on in the P-Cl bond?

Phosphorus (P)

What kind of substance is NCl3?

Polar covalent

What kind of substance is NO?

Polar covalent

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? Ca(2+)(aq) + SO4(2-)(aq) ---> CaSO4(s)

Precipitation

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? Ca2+(aq) + SO4(2-)(aq) ---> CaSO4(s)

Precipitation

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? 2C6H6(l) + 15O2(g) ---> 12CO2(g) + 5H2O(l)

Redox

Is the following reaction classified as an acid-base reaction, redox reaction, or precipitation reaction? 3Br2(aq) + 6OH-(aq) ---> 5Br-(aq) BrO3-(aq) + 3H2O(l)

Redox

Sample 1 and Sample 2 on slide 2 represent the same gas at 298K. Identify the gas that is more likely to deviate from ideality and justify your selection.

Sample 2, pressure increases, particles are closer together, more IMF, particle volume is larger percent of total volume

Which of the following bonds are the most polar? Si-Si, Si-P, Si-S, Si-Cl

Si-Cl

The diagram on slide 39 shows thin-layer chromatograms of the same mixture of two compounds. Based on the chromatograms, which solvent would be most effective at separating the two compounds if the same stationary phase is used for column chromatography?

Solvent C

The reaction between aqueous strontium chloride (SrCl2) and aqueous potassium sulfate (K2SO4) forms a precipitate of strontium sulfate (SrSO4). What is the net ionic equation for the reaction?

Sr2+(aq)+SO42−(aq)→SrSO4(s)

Four electron domains molecules (with no lone pairs)

Tetrahedral; 109.5*

sp3 hybridization

Tetrahedral; 109.5*

The energy required to separate the ions in the Mg(OH)2 crystal lattice into individual Mg2+(g) and OH- (g) ions, as represented in the table on slide 11, is known as the lattice energy of Mg(OH)2(s). As shown in the table, the lattice energy of Sr(OH)2(s) is less than the lattice energy of Mg(OH)2(s). Explain why in terms of periodic properties and Coulomb's law.

The Sr2+ ion is larger than the Mg2+ ion bc it has more occupied energy shells. Coulomb's law states that the force of attraction between cation and anions is inversely proportional to the square of the distance between them. Since the distance between Sr2+ and OH- is longer than the distance between Mg2+ and OH-, the attractive force in Sr(OH)2 are weaker and its lattice energy is smaller.

The elements C and Se have the same electronegativity value, 2.55. What claim about the compound that forms from C and Se can be made?

The carbon-to-selenium bond is nonpolar covalent.

The energy required to dissociate an ionic solid inot gaseous ions (lattice energy) for the compounds NaF and MgF2 is shown in the table on slide 4. On the basis of Coulomb's law, explain the large difference between the lattice energies of NaF and MgF2?

The charge of the MG cation is larger than that of the Na cation.

A student sands the surface of a 6 cm strip of Mg metal and places it into a crucible. The crucible and Mg are massed, placed over a Bunsen burner, and heated strongly in air for 10 minutes. After cooling, the final mass of the crucible and combustion product are taken. The mass of the crucible and Mg before heating if 35.6439 g. The mass of the crucible and combustion product after heating is 37.8901 g. What experimental evidence would best help the student confirm that a new compound has been made and that a chemical change occurred?

The data indicates that the combustion product has a greater mass that the reactant, Mg. The Mg must have reacted with another substance to form a compound with a greater mass.

Coulomb's Law

The force btw charged particles is proportional to the product of the two charges and the force is inversely proportional to the squared radius between them. The force will decrease the further away the particles are. Higher charges and smaller distances btw the charges result in a greater force of attraction. F is proportional to q1q2/r^2

On slide 13 is a representation of a portion of a LiCl crystal. A student wants to draw the structure for KCl, describe how the student should change this drawing to accurately represent KCl. (Assume that KCl and LiCl have similar crystal structures).

The radius of K+ is larger than Li+, so the student should draw a larger black circle. The K+ should be smaller than Cl-.

Three electron domains molecules

Trigonal planar; 120*

sp2 hybridization

Trigonal planar; 120*

What type of spectroscopy would be responsible for the change from 1s22s22p5 to 1s22s22p43s1?

UV-Visible Spectroscopy

Would NaCl dissolve better in hexanes (C6H14) or water H2O?

Water, H2O

A student is given a small mass of baking soda and a sample of vinegar. The student is asked to predict what will happen when the two substances are added together, as well as whether a physical or a chemical process will occur. What prediction should the student make, and how could she provide evidence to justify her answer?

When baking soda and vinegar react together, a gas forming reaction occurs. The formation of carbon dioxide will result in new bonds being made and an endothermic reaction. It takes energy to break apart the baking soda and vinegar, and energy is released when carbon dioxide, water, and sodium acetate are formed. The production of heat from the reaction as well as the observation of gas evolution are evidence of a chemical change.

Element X has the electron configuration 1s22s22p63s23p1, what is the formula for the compound formed btw element X and Cl?

XCl3 (or AlCl3)

A student claims that the first ionization energy for F is greater than that of Br. Do you agree? Explain why or why not in terms of atomic structure and Coulomb's law.

Yes, I agree. The atomic radius of F is smaller than Br. According to Coulomb's law, the force of attraction is inversely proportional to the distance btw charged particles. Since the proton/electrons in F are closer than those in Br, there is a stronger force of attraction and a larger ionization energy.

The potential energy diagram is given for C(triple bond)O on slide 12. A student claims that the curve for a C-O would be less deep and would be shifted to the right of the curve for C(triple bond)O. Do you agree with this claim? Why or why not?

Yes. In the C-O bond, there is less electrons being shared (2 vs 6), so the nucleus of carbon (or oxygen) will be less attracted to the bonding electrons. As a result, the bond length will be longer, and the bond energy will be less than the C-O triple bond.

What is the electron configuration for Mn 2+?

[Ar]3d5

Write the noble gas electron configuration for scandium, Sc.

[Ar]4s23d1

What is the electron configuration for Mn?

[Ar}4s23d5

Write the ground state electron configuration for Chlorine, Cl.

[Ne]3s23p5

What is the electron configuration for Pb 4+?

[Xe]4f145d10

What is the electron configuration for Pb 2+?

[Xe]6s24f145d10

What is the electron configuration for Pb?

[Xe]6s24f145d106p2

In the reaction between C5H5N(aq) and HCl(aq) represented on slide 12, C5H5N acts as...

a Bronsted-Lowry base

Given the following calibration curve for solution X on slide 10. a) If you recorded an absorbance of 0.525, calculate the corresponding molarity of the solution. Mark this on the graph to check your answer is reasonable. b) If the molar mass of the dye used was 791.41 g/mol, how many grams of dye were dissolved in 10.0 mL of the solution measured in part a? c) What is the calculated absorbance for a solution with a concentration of 1.5x10-6 M? Mark this on the graph to check your answer is reasonable. d) Propose a logical reason for the error that occurred with the data point at 6.0 x10-6 M.

a) 5.56x10^-6 M b) 4.40x10^-5 g c) 1.42x10^-7 d) The curvet could have had a fingerprint/scratch; could have not been completely cleaned out and previous substance had a higher concentration; could have not been completely dried causing the solution to be diluted

Solution X has an absorption spectrum shown on the graph on slide 9. A) What would be an appropriate wavelength to gather the absorption data? B) What is the color of the light that is absorbed? C) Predict the color of this solution. D) A solution with an unknown amount of the same solute, X, was prepared and graphed as shown. How is the new solution (unknown concentration) different from the first one? How is it the same?

a) 620 nm b) orange c) blue d) The solutions are the same color. They are both blue because they both absorb orange light. The absorption of the top one is 2x the absorption of the bottom one. Therefore, the top one has a higher concentration.

At 10. atm and 100 K, radon (Rn) deviates from its predicted volume based on the ideal gas law. a) If Radon (Rn) has a smaller volume than predicted, propose an explanation to justify this observation. b) If Radon (Rn) has a larger volume than predicted, propose an explanation to justify this observation.

a) If Rn has a smaller volume it is because the IMF is strong and pulls the particles closer together resulting in a decrease in the volume. b) If Rn has a larger volume than predicted it is because the particles occupy space and the volume of the particles increases the volume.

Two samples of copper (II) sulfate were analyzed using visible light spectroscopy. Sample One absorbed twice as much light as Sample Two. a) What can you deduce about the concentrations of the two solutions? b) What must be true of the solutions in order to get results from this type of spectroscopy? c) Describe the type of changes that occur within the molecule during the process of UV-Vis spectroscopy.

a) The concentration of sample 1 was double the concentration of sample 2. b) They must have a color c) Energy must be absorbed (causing electrons to move to an excited state) and then emitted (the electrons fall to a lower energy state).

Potassium sorbate, KC6H7O2 (molar mass 150. g/mol) is commonly added to diet soft drinks as a preservative. A stock solution of KC6H7O2(aq) of known concentration must be prepared. A student titrates 45.00 mL of the stock solution with 1.25 M HCl(aq) a. Write the net-ionic equation for the reaction between KC6H7O2(aq) and HCl(aq). b. A total of 29.95 mL of 1.25 M HCl(aq) is required to reach the equivalence point. Calculate [KC6H7O2] in the stock solution.

a. C6H7O2- + H+ ---> HC6H7O2 b. 0.832 M KC6H7O2

A student titrates 10.0 mL of a 2.000 M HC2H3O2(aq) with an NaOH(aq) solution of unknown concentration. The student monitors the pH during the titration. The titration curve on slide 6 was created using the experimental data presented in the table. a. Write the balanced net ionic equation for the reaction that occurs when HC2H3O2(aq) and NaOH(aq) are combined. b. Calculate the molar concentration of the NaOH(aq) solution.

a. HC2H3O2 + OH- ---> C2H3O2- + H2O b. 1.43 M NaOH

A student learns that ionic compounds have significant covalent character when a cation has a polarizing effect on a large anion. As a result, the student hypothesizes that salts composed of small cations and large anions should have relatively low melting points. a. Select two compounds from the table on slide 1 and explain how the data supports the student's hypothesis. b. When fluoride compounds are dissolved in water, hydroxide ions are produced. Write the net ionic equation for the reaction that occurs when one of the fluorides in the table is combined with water. (Hint: HF doesn't dissociate appreciably in water.)

a. LiI and KI: LiI has a small cation and a large anion, and KI has a large cation and the same large anion. The melting point of LiI (with its smaller cation) is lower than that of KI OR LiI and LiF: Lil has a small cation and a large anion, and LiF has the same small cation and small anion. The melting point of LiI (with its larger anion) is lower than that of LiF. OR LiI and NaF: LiI has a small cation and a large anion, and NaF has a relatively small cation and a small anion. The melting point of LiI (with its larger anion) is lower than that of NaF. b. Either LiF or NaF is acceptable. F- + H2O <---- ----> HF + OH-

Serine and glycine (shown on slide 6) are both amino acids where serine is polar and glycine is nonpolar. The two amino acids are not labelled and must be identified. a. Explain why thin layer chromatography is more appropriate than paper chromatography in this case. b. Describe how to set up a thin layer chromatography experiment that will help identify the two amino acids. c. Draw a chromatogram that would represent what we know about the two amino acids.

a. Paper chrom. separated colored mixtures and these amino acids don't seem to be colored. TLC can separate and ID colorless solutions with UV light or ninhydrin. b) Thin sheet of plastic coated with a very polar substance (aluminum) and the two samples are placed near the bottom of the sheet and labelled in pencil. Then, place this sheet in a solvent that will fluoresce in UV light just touching the sheet at the bottom. Time would then be allowed to pass until the leading edge of the solvent is near the top. After this, shine UV light on your sheet and mark in pencil the dark spots. Then, measure the distance of the solvent's travel and the samples' travel from your original sample location. c) see slide 7

Which of the following statements, if true, would support the claim that the NO3− ion, represented on slide 10, has three resonance structures? a. The NO3- ion is not a polar species. b. The oxygen-to-nitrogen-to-oxygen bond angles are 90*. c. One of the bonds in NO3- is longer than the other two. d. One of the bonds in NO3- is shorter than the other two.

a. The NO3- ion is not a polar species.

Which of the following claims about a P-Cl bond is true? The electronegativity of P is 2.5 and Cl is 3.0. a. the partial positive charge is on the phosphorus. b. the dipole arrow points toward the phosphorus. c. there is a sea of electrons between phosphorus and chlorine d. the bond between phosphorus adn chlorine is nonpolar

a. the partial positive charge is on the phosphorus

Zn(s) + 2HCl(aq) ---> ZnCl2(aq) + H2(g) When a student adds 50.0 mL of 1.00 M HCl to 2.35 g of Zn, a reaction occurs according to the equation above. a.) When the reaction is complete at 273 K and 1.0 atm, what volume of H2(g) is produced? b.) Which of the following changes would increase the volume of H2(g) produced in a? i. doubling the mass of Zn ii. doubling the volume of HCl iii. doubling the concentration of HCl

a.) 0.560 L H2 b.) i. no effect ii. increases iii. increases

6H+ (aq) + 2MnO4-(aq) + 5H2C2O4(aq) ---> 10CO2(g) + 8H2O(l) + 2Mn2+(aq) A student dissolved a 0.139 g sample of oxalic acid, H2C2O4 in water in an Erlenmeyer flask. Then the student titrated the H2C2O4 solution in the flask with a solution of KMnO4 which has a dark purple color. The balanced chemical equation for the reaction that occurred during the titration is shown above. a.) The student used a 50.0 mL buret to add the KMnO4(aq) to the H2C2O4(aq) until a faint lavender color was observed in the flask, an indication that the end point of the titration had been reached. the initial and final volume readings of the solution in the buret are shown on slide 6. Write down the initial reading and the final reading and use them to determine the volume of KMnO4(aq) that was added during the titration. b.) Given that the concentration of KMnO4(aq) was 0.0235 M, calculate the number of moles of MnO4- ions that completely reacted with the H2C2O4. d.) The student proposes to perform another titration using a 0.139 g sample of H2C2O4 but this time using 0.00143 M KMnO4(aq) in the buret. Would this titrant concentration be a reasonable choice to use if the student followed the same procedure and used the same equipment as before? justify your response?

a.) 26.20 mL of KM nO4 added b.)6.16x10^-4 mol MnO4- c.) No, the titrant is so dilute that volume of titrant needed would exceed the capacity of the 50 mL buret.

2MnO4-(aq) + 5H2O2(aq) + 6H+(aq) ---> 2Mn2+(aq) + 5O2(g) + 8H2O(l) A student was given the task of determining the molarity of an unkown concentration of H2O2(aq). She analyzed a 10.0mL sample of H2O2(aq) by titrating it with 0.0330 M KMnO4 which has a dark purple color. The balanced chemical equation for the reaction that occurred during the titration is shown above. A total of 10.69 mL of 0.0330 M KMnO4 was required to reach the equivalence point. a.) Calculate the number of moles of MnO4- that reacted completely with the H2O2. b.) Calculate the {H2O2] in the solution.

a.) 3.53x10^-4 mol MnO4- b.) 0.0882 M H2O2

C3H8(g) + 5O2(g) ---> 3CO2(g) + 4H2O(g) Propane burns in air to produce carbon dioxide and water according to the above equation. 44.1 g of propane and 44.1 g of oxygen are added to a rigid vessel. The reaction is parked and goes to completion. a.) When the reaction is complete at 273 K and 1.0 atm, what mass of CO2(g) is produced? b.) What effect would each of the following changes have on the mass of CO2(g) produced in a? i. doubling the mass of C2H8(g) ii. doubling the mass of O2(g)

a.) 36.4 g CO2 b.) i. no effect ii. increases

Pentane, C5H12 and Octane C8H18, are both hydrocarbons. a.) Identify the type of intermolecular forces present. b.) Predict the substances that would have a higher vapor pressure and justify your claim.

a.) Both substances only have LDF b.) The pentane would have a higher vapor pressure. Pentane has fewer electrons than octane leading to less polarizability and therefore weaker LDF IMF. the pentane will therefore vaporize more readily and result in a higher vapor pressure.

CO2 melts at -78 degrees C and SiO2 melts at 1,650 degrees C a.) Identify the type of solid each substance forms. b.) Justify the difference in melting points.

a.) CO2 - molecular solid and SiO2 - Covalent Network b.) CO2 is a molecular solid therefore when it melts only IMF's are broken. These are the weakest forces so very little energy is required to melt which results in a very low boiling point. SiO2 is a covalent network solid therefore when it melts covalent bonds must be broken. Covalent bonds require a large amount of energy to be broken which results in a very high boiling point.

Co(s) ---> Co(2+)(aq) + 2e- Ag(1+)(aq) + e- ---> Ag(s) The half-reactions for the oxidation-reduction between Co(s) and Ag(1+)(aq) are represented above. a.) Which substance is being oxidized and which substance is being reduced? b.) Write the balanced net ionic equation for the oxidation-reduction reaction based on the half-reactions above.

a.) Co is being oxidized and Ag is being reduced b.) Co(s) + 2Ag(1+)(aq) ---> Co(2+)(aq) + 2Ag(s)

Cr(s) ---> Cr(3+)(aq) + 3e- Ag(1+)(aq) + e- ---> Ag(s) The half-reactions for the oxidation-reduction between Cr(s) and Ag(1+)(aq) are represented above. a.) Which substance is being oxidized and which substance is being reduced? b.) Write the balanced net ionic equation for the oxidation-reduction reaction based on the half-reactions above.

a.) Cr is being oxidized and Ag is being reduced b.) Cr(s) + 3Ag(1+)(aq) + 3e- ---> Cr(3+)(aq) + 3e- + 3 Ag(s)

The boiling point of HF is 293K whereas the boiling point of F2 is 85K. a.) Determine the type(s) of intermolecular forces present. b.) Explain the difference in boiling points based on their intermolecular forces.

a.) H-F would have hydrogen-bonding, dipole-dipole, and LDF F-F would have LDF only b.) H-F has a higher boiling point because the hydrogen bonding and LDF are stronger and hold the molecules together more tightly than the LDF only in F2, this means that it takes more energy to separate the molecules in H-F.

HC2H3O2(aq) + OH-(aq) ---> C2H3O2-(aq) + H2O(l) A student performed a titration of HC2H3O2(aq) with KOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is shown above. a.) Identify both of the Bronsted-Lowry conjugate acid-base pairs in the neutralization reaction above. For each pair, label the acid and the base. b.) In terms of the species in the reaction, explain what occurs during the reaction that identifies it as an acid-base reaction.

a.) HC2H3O2(aq) and C2H3O2-(aq) are a conjugate acid-base pair and OH-(aq) and H2O(l) are a conjugate acid-base pair. b.) HC2H3O2(aq) donates a proton and becomes C2H3O2-(aq)

Al(s) + Ni(NO3)2(aq) ---> Al(NO3)3(aq) + Ni(s) The reaction between solid aluminum and aqueous nickel (II) nitrate is represented by the equation shown above. Based on the equation, answer the following: a.) Write the oxidation half-reaction and reduction half-reaction. b.) Write the balanced net ionic equation for the oxidation-reduction reaction shown above.

a.) Oxidation Half-Reaction: Al(s) ---> Al(3+)(aq) + 3e- Reduction Half-Reaction: Ni(2+)(aq) + 2e- ---> Ni(s) b.) 2Al(s) + 3Ni(2+)(aq) ---> 2Al(3+)(aq) + 3Ni(s)

Will an aqueous solution of NH4(aq) be acidic, basic, or neutral?

acidic

Two representation of sulfite ion are shown on slide 5. Indicate the formal charge on each atom. Which structure is better?

all the O in the first structure at -1 and the S is +1; 2 of the O in seconds structure are -1 and the other is 0 and the S is 0; the second structure is better

Of the following, the best explanation for the fast that most liquids cannot be easily compressed is that the molecules in a liquid: a. are in constant motion b. are relatively close together c. have varying densities d. have a fixed volume e. move slower as temperature decreases

Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor? a. H - O bonds break as H - H and O - O bonds form. b. Hydrogen bonds between H2O molecules are broken. c. Covalent bonds between H2O molecules are borken. d. Ionic bonds between H+ ions and OH- ions are broken. e. Covalent bonds between H+ and H2O molecules becomes more effective.

b. Hydrogen bonds between H2O molecules are broken.

A student is asked to formulate a hypothesis about what would happen to sodium metal when it is placed in water. Which of the following hypotheses indicates that the student thinks a chemical change will occur? a. If sodium is added to water, it will dissolve. b. If sodium is added to water, heat and light will be released. c. If sodium is added to water, the total mass will be the same. d. If sodium is added to water, the water will remain a clear, colorless liquid.

b. If sodium is added to water, heat and light will be released.

Will an aqueous solution of NaClO(aq) be acidic, basic, or neutral?

basic

Will an aqueous solution of NaF(aq) be acidic, basic, or neutral?

basic

What is the molecular geometry of H2S?

bent

Which element has the larger ionization energy: beryllium or magnesium?

beryllium

Visible Light Spectroscopy

concerned with the part of the electromagnetic spectrum that we can see; associated with transition in electronic energy levels

What type of solid is SiO2(s) an example of?

covalent network solid

What type of solid is diamond (C) an example of?

covalent network solid

Fe(s) + 2HCl (aq) ---> FeCl2 (aq) + H2(g) When a student adds 30.0 mL of 1.00 M HCl to 0.56 g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273 K and 1.0 atm, which of the following is true? a. HCl is in excess, and 0.100 mol of HCl remains unreacted. b. HCl is in excess, and 0.020 mol of HCl remains unreacted. c. 0.015 mol of FeCl2 has been produced. d. 0.22 L of H2 has been produced.

d. 0.22 L of H2 has been produced.

Which of the following scientific claims about the bond in the molecular compound HF is most likely to be true? a. There is a partial negative charge on the H atom. b. Electrons are shared equally between the H and F atoms. c. The bond is extremely weak. d. The bond is highly polar.

d. the bond is highly polar

Bond polarity

difference in electronegativity values of two elements

Metallic bonds

electrons not associated with a single atom or molecule (delocalized electrons); occurs between metals atoms (it can be for just one type of meal, a pure substance, or for different types of metal called an alloy)

Nonpolar Covalent bonds

electrons shared equally; Visual of electron sharing: (A--:--B); no bond dipole moment; electronegativity difference is < 0.5

Polar Covalent bonds

electrons shared unequally; visual of electron sharing: (A---:-B); bond dipole moment is partial; electronegativity difference is 0.5-1.7

A particle-level diagram of a metallic element is shown on slide 6. Typically, metals are both malleable and ductile. The best explanation for these properties is that the electrons involved in bonding among metal atoms are

equally shared and form nondirectional bonds

Would C3H8 dissolve better in hexanes (C6H14) or water H2O?

hexanes C6H14

Would CO2 dissolve better in hexanes (C6H14) or water H2O?

hexanes C6H14

Conductivity of metallic solid

high

Is the melting point of a covalent network solid high or low?

high

Is the melting point of a metallic solid high or low?

high

Is the melting point of an ionic solid high or low?

high

Under what temperature and pressure conditions do gases behave most ideally?

high temperature and low pressure

Infrared Spectroscopy

higher in energy than microwaves, but less than visible light; measures the vibration of the atoms and allows the determination of the functional groups present in a molecule; generally, lighter atoms and stronger bonds tends to vibrate at higher frequencies; is associated with transitions in molecular vibrational levels

Soluble or Insoluble: AgCl

insoluble

Soluble or Insoluble: BaCrO4

insoluble

What is the bond type in the compound Na2O?

ionic

What type of solid if table salt (NaCl) an example of?

ionic solid

What is the molecular geometry of CO2?

linear

Is the melting point of a molecular solid high or low?

low

Microwave Radiation

lower in energy than visible light; causes particles to rotate when it strikes them due to the interaction of the dipole of the molecules interacting with the electromagnetic field of the microwave photons; associated with transitions in molecular rotational levels

What type of solid is Cu(s) an example of?

metallic solid

What type of solid is sucrose (C12H22O11) an example of?

metallic solid

What type of solid is H2O an example of?

molecular solid

Will an aqueous solution of KCl(aq) be acidic, basic, or neutral?

neutral

Conductivity of covalent network solid in aqueous solution

none

Conductivity of ionic solid

none

Conductivity of molecular solid

none

Conductivity of molecular solid in aqueous solution

none

Conductivity of metallic solid in aqueous solution

none (doesn't dissolve)

Conductivity of covalent network solid

none (except graphite)

Is BeCl2 polar or nonpolar?

nonpolar

Is CBr4 polar or nonpolar?

nonpolar

Polar or nonpolar? slide 25

nonpolar

Polar or nonpolar? slide 27

nonpolar

Polar or nonpolar? slide 30

nonpolar

Polar or nonpolar? slide 31

nonpolar

Polar or nonpolar? slide 33

nonpolar

What is the bond type in the compound C2H6?

nonpolar covalent

What is the bond type in the compound O2?

nonpolar covalent

Is CH2O polar or nonpolar?

polar

Is CH3Br polar or nonpolar?

polar

Polar or nonpolar? slide 24

polar

Polar or nonpolar? slide 26

polar

Polar or nonpolar? slide 28

polar

Polar or nonpolar? slide 29

polar

Polar or nonpolar? slide 32

polar

What is the bond type in the compound Cl2O?

polar covalent

Draw a particle diagram to represent water in a puddle as it starts to evaporate.

see slide 1

What is the Lewis diagram for carbon tetrafluoride, CF4?

see slide 15

What is the Lewis diagram for sulfur dioxide, SO2?

see slide 16

What is the Lewis diagram for a nitrate ion, NO3-1?

see slide 17

What is the Lewis diagram for Xenon tetrafluoride, XeF4?

see slide 18

Draw the Lewis diagram for the formate ion HCO2-1 and include all resonance structures.

see slide 19

The particle-level diagram on slide 2 represents the structure of solid KF. Although the molar mass of KCL is greater than that of KF, the density of KCL is actually less than that of KF. Which of the following representations of the structure of KCL best helps to explain this phenomenon?

see slide 3

2H2O2(aq) ---> 2H2O(l) + O2(g) Hydrogen peroxide, H2O2, decomposes according to the equation above. This reaction is thermodynamically favorable at room temperature. A particulate representation of the reactants is shown on slide 3. Draw the particulate representation of all the molecules that would be produced from these four reactant molecules.

see slide 4

Copper atoms and zinc atoms have the same atomic radius, 135 picometers. Based on this information, draw a diagram that represents an alloy containing only copper and zinc atoms?

see slide 5

Steel is an alloy containing Fe atoms and C atoms. Draw a diagram that represents the particle-level structure of steel.

see slide 7

Which of the following Lewis diagrams best represents the bonding in the N2O molecule, considering formal charges?

see slide 9

Which element has the highest electron affinity (most negative) germanium or selenium?

selenium

Soluble or Insoluble: (NH4)2SO4

soluble

Soluble or Insoluble: Fe(NO3)2

soluble

Soluble or Insoluble: Na2PO4

soluble

What is the hybridization of each indicated atom on slide 4? How many sigma and pi bonds are there?

sp2 and sp; 7 sigma and 1 pi

What is the hybridization of each indicated atom on slide 3? How many sigma and pi bonds are there?

sp3 and sp; 5 sigma and 2 pi

Determine the formal charge for each atom in the possible Lewis diagrams for the thiocyanate ion and then decide which of the three structures is the dominant one. see slide 21

the third one

Ionic bonds

transferring electrons (usually involves a metal and a nonmetal)--this type of attraction is a coulombic or electrostatic attraction between a cation and an anion; Visual of electron sharing: (A :B); Bond dipole movement is positive and negative; electronegativity difference is > 1.7

What is the molecular geometry of BF3?

trigonal planar

What is the molecular geometry of NH3?

trigonal pyramidal

Would CH2O dissolve better in hexanes (C6H14) or water H2O?

water, H2O

Nitric acid, HNO3, is a common strong acid very corrosive when concentrated. The Lewis diagram of nitric acid is shown below, and the nitrogen-oxygen bonds labeled as x, y, and z. Accurately compare the lengths between the x, y, and z bonds. see slide 20

AP Chemistry Midterm

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