chemistry

Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125oC?

C

A sample of carbonate rock is a mixture of CaCO3 and MgCO3. The rock is analyzed in a laboratory, and the results are recorded in the table above. Which columns in the table provide all the information necessary to determine the mole ratio of Ca to Mg in the rock? A. 1, 2, 5 B. 2, 5, 6 C. 3, 4, 6, 7 D. 2, 3, 4, 5

C. 3, 4, 6, 7

If 200. mL of 0.60 M MgCl2(aq) is added to 400. mL of distilled water, what is the concentration of Mg2+(aq) in the resulting solution? (Assume volumes are additive). A. 0.20 M B. 0.30 M C. 0.40 M D. 0.60 M E. 1.2 M

E. 1.2 M

Which of the following equations best represents the species that react and the species that are produced when CaCO3(s) and HCl(aq) are combined? A. 2H+(aq)+CaCO3(s)→Ca2+(aq)+CO32−(aq)+H2(g) B. 2H+(aq)+CaCO3(s)→Ca2+(aq)+H2O(l)+CO2(g) C. 2H+(aq)+CaCO3(s)→Ca2+(aq)+2OH−(aq)+CO(g) D. 2HCl(aq)+CaCO3(s)→Ca2+(aq)+H2O(l)+CO2(g)+2Cl−(aq)

B. 2H+(aq)+CaCO3(s)→Ca2+(aq)+H2O(l)+CO2(g)

HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l)ΔH°=−57.1kJ/molrxn The chemical equation above represents the reaction between HCl(aq) and NaOH(aq). When equal volumes of 1.00MHCl(aq) and 1.00MNaOH(aq) are mixed, 57.1kJ of heat is released. If the experiment is repeated with 2.00MHCl(aq), how much heat would be released? A. 28.6kJ B. 57.1kJ C. 85.7kJ D. 114kJ

B. 57.1kJ

2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g) According to the reaction represented above, about how many grams of aluminum (atomic mass 27 g) are necessary to produce 0.50 mol of hydrogen gas at 25ºC and 1.00 atm? A. 1.0 g B. 9.0 g C. 14 g D. 27 g

B. 9.0 g

2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g) According to the reaction represented above, about how many grams of aluminum (atomic mass 27 g) are necessary to produce 0.50 mol of hydrogen gas at 25ºC and 1.00 atm? A. 1.0 g B. 9.0 g C. 14 g D. 27 g E. 56 g

B. 9.0 g

The first five ionization energies of an unknown element are listed in the table above. Which of the following statements correctly identifies the element and cites the evidence supporting the identification? A. Na, because of the large difference between the first and the second ionization energies B. Al, because of the large difference between the third and fourth ionization energies C. Si, because the fifth ionization energy has the greatest value D. P, because a neutral atom of P has five valence electrons

B. Al, because of the large difference between the third and fourth ionization energies

Addition of sulfurous acid (a weak acid) to barium hydroxide (a strong base) results in the formation of a precipitate. The net ionic equation for this reaction is A. 2 H+(aq) + 2 OH-(aq) ⇄ 2 H2O(l) B. H2SO3(aq) + Ba2+(aq) + 2 OH-(aq) ⇄ BaSO3(s) + 2 H2O(l) C. 2 H+(aq) + SO32-(aq) + Ba2+(aq) + 2 OH-(aq) ⇄ BaSO3(s) + 2 H2O(l) D. H2SO3(aq) + Ba2+(aq) + 2 OH-(aq) ⇄ Ba2+(aq) + SO32-(aq) + 2 H2O(l) E. H2SO3(aq) + Ba(OH)2(aq) ⇄ BaSO3(s) + 2 H2O(l)

B. H2SO3(aq) + Ba2+(aq) + 2 OH-(aq) ⇄ BaSO3(s) + 2 H2O(l)

The photoelectron spectra for H and He are represented above. Which of the following statements best accounts for the fact that the peak on the He spectrum is farther to the left and higher than the peak on the H spectrum? A. He has an additional valence electron in a higher energy level than the valence electron in H. B. He has a greater nuclear charge than H and an additional electron in the same energy level. C. He has a completely filled valence shell in which the electrons are a greater distance from the nucleus than the distance between the H nucleus and its electron. D. It takes longer for the electrons in He to be removed due to the higher nuclear mass of He.

B. He has a greater nuclear charge than H and an additional electron in the same energy level.

Based on Coulomb's Law and the information in the table above, which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution? A. Li+ B. Na+ C. Ca2+ D. In3+

B. Na+

When a sample of oxygen gas in a closed container of constant volume is heated until its absolute temperature is doubled, which of the following is also doubled? A. The density of the gas B. The pressure of the gas C. The average velocity of the gas molecules D. The number of molecules per cm3 E. The potential energy of the molecules

B. The pressure of the gas

If 50. mL of 1.0 M NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resulting solution is A. 0.025 M B. .050 M C. 0.10 M D. 0.50 M E. 1.0 M

A. 0.025 M

A solution is prepared by adding 16 g of CH3OH (molar mass 32 g) to 90. g of H2O (molar mass 18 g). The mole fraction of CH3OH in this solution is closest to which of the following? A. 0.1 B. 0.2 C. 0.3 D. 0.4 E. 0.6

A. 0.1

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? A. 0.200M B. 0.500M C. 1.00M D. 5.00M

A. 0.200M

How many grams of CaCl2 (molar mass =111g/mol) are needed to prepare 100.mL of 0.100MCl−(aq) ions? A. 0.555g B. 1.11g C. 2.22g D. 5.55g

A. 0.555g

NH4NO3(s) → N2O(g) + 2 H2O(g) A 0.03 mol sample of NH4NO3(s) is placed in a 1 L evacuated flask, which is then sealed and heated. The NH4NO3(s) decomposes completely according to the balanced equation above. The total pressure in the flask measured at 400 K is closest to which of the following? (The value of the gas constant, R, is 0.082 L atm mol-1 K-1.) A. 3 atm B. 1 atm C. 0.5 atm D. 0.1 atm

A. 3 atm

2 N2H4(g) + N2O4(g) → 3 N2(g) + 4 H2O(g) When 8.0 g of N2H4 (32 g mol-1) and 92 g of N2O4 (92 g mol-1) are mixed together and react according to the equation above, what is the maximum mass of H2O that can be produced? A. 9.0 g B. 18 g C. 36 g D. 72 g

A. 9.0 g

Two pure elements react to form a compound. One element is an alkali metal, X, and the other element is a halogen, Z. Which of the following is the most valid scientific claim that can be made about the compound? A. It has the formula XZ2. B. It does not dissolve in water. C. It contains ionic bonds. D. It contains covalent bonds.

C. It contains ionic bonds.

Equal masses of three different ideal gases, X, Y, and Z, are mixed in a sealed rigid container. If the temperature of the system remains constant, which of the following statements about the partial pressure of gas X is correct? A. It is equal to ⅓ the total pressure B. It depends on the intermolecular forces of attraction between molecules of X, Y, and Z. C. It depends on the relative molecular masses of X, Y, and Z. D. It depends on the average distance traveled between molecular collisions. E. It can be calculated with knowledge only of the volume of the container.

C. It depends on the relative molecular masses of X, Y, and Z.

What remains in the reaction vessel after equal masses of K(s) and Cl2(g) have reacted until either one or both of the reactants have been completely consumed? A. KCl only B. KCl and K only C. KCl and Cl2 only D. KCl , K, and Cl2

C. KCl and Cl2 only

(A) BeCl2 (B) SO2 (C) N2 (D) O2 (E) F2 Is the molecule in which the intramolecular forces are strongest A. BeCl2 B. SO2 C. N2 D. O2 E. F2

C. N2

Based on Coulomb's law and the information in the table above, which of the following anions is most likely to have the strongest interactions with nearby water molecules in an aqueous solution? A. Cl- B. I- C. S2- D. Te2-

C. S2-

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.

The table above shows the first ionization energy and atomic radius of several elements. Which of the following best helps to explain the deviation of the first ionization energy of oxygen from the overall trend? A. The atomic radius of oxygen is greater than the atomic radius of fluorine. B. The atomic radius of oxygen is less than the atomic radius of nitrogen. C. There is repulsion between paired electrons in oxygen's 2p orbitals. D. There is attraction between paired electrons in oxygen's 2p orbitals.

C. There is repulsion between paired electrons in oxygen's 2p orbitals.

In the reaction represented above, the number of MnO4- ions that react must be equal to which of the following? A. One-fifth the number of Fe2+ ions that are consumed B. Eight times the number of H+ ions that are consumed C. Five times the number of Fe3+ ions that are produced D. One-half the number of H2O molecules that are produced

A. One-fifth the number of Fe2+ ions that are consumed

Which of the following gases deviates most from ideal behavior? A. SO2 B. Ne C. CH4 D. N2

A. SO2

The reaction between C6H12O6 and O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2 was produced. Which of the following must be true? A. The initial amount of C6H12O6 in the container must have been 0.10mol. B. Exactly 0.30mol of C6H12O6 must have reacted because C atoms were conserved. C. Exactly 0.40mol of O2 of must have reacted because the temperature and container volume are the same. D. More than 0.60mol of O2 must have reacted because it was present in excess.

A. The initial amount of C6H12O6 in the container must have been 0.10mol.

At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same A. average molecular kinetic energy B. average molecular speed C. volume D. effusion rate

A. average molecular kinetic energy

The elements K and Cl react directly to form the compound KCl according to the equation above. Refer to the information above and the table below to answer the questions that follow. A two column table shows the delta H degree values in kilojoules per molecule sub r x n for five different processes. The data presented in the table appears as follows. K solid gives K gas: v; K gas gives K cation gas plus e anion: w; Cl 2 gas gives 2 Cl gas: x; Cl gas plus e anion gives Cl anion gas: y; K cation gas plus Cl anion gas gives K Cl solid: z. CI2(g) + 2e-→ 2 CI-(g) Which of the following expressions is equivalent to ΔHo for the reaction represented above? A. x + y B. x - y C. x + 2y D. x2−y

C. x + 2y

Permanganate and oxalate ions react in an acidified solution according to the balanced equation above. How many moles of CO2(g) are produced when 20. mL of acidified 0.20 M KMnO4 solution is added to 50. mL of 0.10 M Na2C2O4 solution? A. 0.0040 mol B. 0.0050 mol C. 0.0090 mol D. 0.010 mol E. 0.020 mol

D. 0.010 mol

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.

When a 3.22 g sample of an unknown hydrate of sodium sulfate, Na2SO4 ⋅ H2O(s), is heated, H2O (molar mass 18 g) is driven off. The mass of the anhydrous Na2SO4(s) (molar mass 142 g) that remains is 1.42 g. The value of x in the hydrate is A. 0.013 B. 1.8 C. 6.0 D. 10. E. 20.

D. 10.

Which of the following ground-state electron configurations represents the atom that has the lowest first-ionization energy? A. 1s22s1 B. 1s22s22p2 C. 1s22s22p6 D. 1s22s22p63s1

D. 1s22s22p63s1

C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) In the reaction represented above, what is the total number of moles of reactants consumed when 1.00 mole of CO2(g) is produced? A. 0.33 mol B. 1.33 mol C. 1.50 mol D. 2.00 mol E. 6.00 mol

D. 2.00 mol

In the reaction represented above, what mass of HF is produced by the reaction of 3.0 x 1023 molecules of H2 with excess F2 ? (Assume the reaction goes to completion.) A. 1.0 g B. 4.0 g C. 10. g D. 20. g E. 40. g

D. 20. g

Ca3(PO4)2(s) + . . . H3PO4(l) → . . . Ca(H2PO4)2(s) When the equation above is balanced and all coefficients are reduced to lowest whole-number terms, what is the coefficient for H3PO4(l) ? A. 1 B. 2 C. 3 D. 4 E. 5

D. 4

C3H8(g) + ...O2(g) → ...H2O(g) + ...CO2(g) When the equation for the reaction represented above is balanced and all coefficients are reduced to the lowest whole-number terms, the coefficient for O2(g) is A. 1 B. 2 C. 3 D. 5 E. 6

D. 5

In a one-person spacecraft, an astronaut exhales 880g of CO2(g) (molar mass 44g/mol) per day. To prevent the buildup of CO2(g) in the spacecraft, a device containing LiOH(s) is used to remove the CO2(g), as represented by the equation above. What mass of LiOH(s) (molar mass 24g/mol) is needed to react with all of the CO2(g) produced by an astronaut in one day? A. 40.g B. 240g C. 480g D. 960g

D. 960g

To gravimetrically analyze the silver content of a piece of jewelry made from an alloy of Ag and Cu, a student dissolves a small preweighed sample in HNO3(aq). Ag+(aq)and Cu2+(aq) ions form in the solution. Which of the following should be the next step in the analytical process? A. Centrifuging the solution to isolate the heavier ions B. Evaporating the solution to recover the dissolved nitrates C. Adding enough base solution to bring the pH up to 7.0 D. Adding a solution containing an anion that forms an insoluble salt with only one of the metal ions

D. Adding a solution containing an anion that forms an insoluble salt with only one of the metal ions

Which of the following best explains why the combustion reactions represented in the table are exothermic? A. The number of bonds in the reactant molecules is greater than the number of bonds in the product molecules. B. The number of bonds in the reactant molecules is less than the number of bonds in the product molecules. C. The energy required to break the bonds in the reactants is greater than the energy released in forming the bonds in the products. D. The energy required to break the bonds in the reactants is less than the energy released in forming the bonds in the products.

D. The energy required to break the bonds in the reactants is less than the energy released in forming the bonds in the products.

Which of the following best helps to explain why the electron affinity of Br has a greater magnitude than that of I? A. Br has a lower electronegativity than I does. B. Br has a lower ionization energy than I does. C. An added electron would go into a new shell in Br but not in I. D. There is a greater attraction between an added electron and the nucleus in Br than in I.

D. There is a greater attraction between an added electron and the nucleus in Br than in I.

These questions refer to the following compounds at 25°C and 1.0 atm. (A) CO2 (B) PbO2 (C) CaO (D) N2O5 (E) Cu2O Which of the following compounds at 25°C and 1.0 atm contains an element in a +1 oxidation state? A. CO2 B. PbO2 C. CaO D. N2O5 E. Cu2O

E. Cu2O

cotton ball The experimental apparatus represented above is used to demonstrate the rates at which gases diffuse. When the cotton balls are placed in the ends of a tube at the same time, the gases diffuse from each end and meet somewhere in between, where they react to form a white solid. Which of the following combinations will produce a solid closest to the center of the tube? A. HCl and CH3NH2 B. HCl and NH3 C. HBr and CH3NH2 D. HBr and NH3

A. HCl and CH3NH2

Which of the following represents an electron configuration that corresponds to the valence electrons of an element for which there is an especially large jump between the second and third ionization energies? (Note: n represents a principal quantum number equal to or greater than 2.) A. ns2 B. ns2np1 C. ns2np2 D. ns2np3

A. ns2

Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively? A. 242 pm, 633 kJ/mol B. 242 pm, 419 kJ/mol C. 120 pm, 633 kJ/mol D. 120 pm, 419 kJ/mol

B. 242 pm, 419 kJ/mol

Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3(aq) into their beakers. The reaction between the copper in the mixture and the HNO3(aq) is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu2+(aq). The solutions were then diluted with distilled water to known volumes. The students determined that the reaction produced 0.010 mol of Cu(NO3)2 . Based on the measurement, what was the percent of Cu by mass in the original 2.00 g sample of the mixture? A. 16% B. 32% C. 64% D. 96%

B. 32%

The figure above represents three sealed 1.0 L vessels, each containing a different inert gas at 298 K. The pressure of Ar in the first vessel is 2.0 atm. The ratio of the numbers of Ar, Ne, and He atoms in the vessels is 2:1:6, respectively. After all the gases are combined in a previously evacuated 2.0 L vessel, what is the total pressure of the gases at 298 K? A. 3.0 atm B. 4.5 atm C. 9.0 atm D. 18 atm

B. 4.5 atm

2 H2O(l) + 4 MnO4-(aq) + 3 ClO2-(aq) → 4 MnO2(s) + 3 ClO4-(aq) + 4 OH-(aq) According to the balanced equation above, how many moles of ClO2-(aq) are needed to react completely with 20. mL of 0.20 M KMnO4 solution? A. 0.0030 mol B. 0.0053 mol C. 0.0075 mol D. 0.013 mol E. 0.030 mol

A. 0.0030 mol

3 Ag(s) + 4 HNO3 → 3 AgNO3 + NO(g) + 2 H2O The reaction of silver metal and dilute nitric acid proceeds according to the equation above. If 0.10 mole of powdered silver is added to 10. milliliters of 6.0-molar nitric acid, the number of moles of NO gas that can be formed is A. 0.015 mole B. 0.020 mole C. 0.030 mole D. 0.045 E. 0.090

A. 0.015 mole

When the actual gas volume is greater than the volume predicted by the ideal gas law, the explanation lies in the fact that the ideal gas law does NOT include a factor for molecular. A. volume B. mass C. velocity D. attractions E. shape

A. volume

A 20.0-milliliter sample of 0.200-molar K2CO3 solution is added to 30.0 milliliters of 0.400-molar Ba(NO3)2 solution. Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after reaction is A. 0.150 M B. 0.160 M C. 0.200 M D. 0.240 M E. 0.267 M

B. 0.160 M

Using the wavelength information provided above, what is the color of the light? A. Red B. Orange C. Yellow D. Blue

B. Orange

How many moles of Na+ ions are in 100.mL of 0.100M Na3PO4(aq) ? A. 0.300mol B. 0.100mol C. 0.0300mol D. 0.0100mol

C. 0.0300mol

A 40.0 mL sample of 0.25 M KOH is added to 60.0 mL of 0.15 M Ba(OH)2. What is the molar concentration of OH-(aq) in the resulting solution? (Assume that the volumes are additive.) A. 0.10 M B. 0.19 M C. 0.28 M D. 0.40 M E. 0.55 M

C. 0.28 M

Which of the following molecules contains only single bonds? A. CH3COOH B. CH3CH2COOCH3 C. C2H6 D. C6H6 E. HCN

C. C2H6

Which of the following ions has the same number of electrons as Br - ? A. Ca2+ B. K+ C. Sr2+ D. I- E. Cl-

C. Sr2+

In an insulated cup of negligible heat capacity, 50. g of water at 40.°C is mixed with 30. g of water at 20.°C. The final temperature of the mixture is closest to A. 22°C B. 27°C C. 30.°C D. 33°C E. 38°C

D. 33°C

Which of the following compounds contains both ionic and covalent bonds? A. SO3 B. C2H5OH C. MgF2 D. H2S E. NH4Cl

E. NH4Cl

In which of the following species does sulfur have the same oxidation number as it does in H2SO4? A. H2SO3 B. S2O32- C. S2- D. S8 E. SO2Cl2

E. SO2Cl2

Two flexible containers for gases are at the same temperature and pressure. One holds 0.50 gram of hydrogen and the other holds 8.0 grams of oxygen. Which of the following statements regarding these gas samples is FALSE? A. The volume of the hydrogen container is the same as the volume of the oxygen container. B. The number of molecules in the hydrogen container is the same as the number of molecules in the oxygen container. C. The density of the hydrogen sample is less than that of the oxygen sample. D. The average kinetic energy of the hydrogen molecules is the same as the average kinetic energy of the oxygen molecules. E. The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.

E. The average speed of the hydrogen molecules is the same as the average speed of the oxygen molecules.

A sample of an unknown gas from a cylinder is collected over water in the apparatus shown above. After all the gas sample has been collected, the water levels inside and outside the gas collection tube are made the same. Measurements that must be made to calculate the molar mass of the gas include all of the following EXCEPT A. atmospheric pressure B. temperature of the water C. volume of gas in the gas-collection tube D. initial and final mass of the gas cylinder E. mass of the water in the apparatus

E. mass of the water in the apparatus

If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO2? A. Benzene, C6H6 B. Cyclohexane, C6H12 C. Glucose, C6H12O6 D. Methane, CH4

A. Benzene, C6H6

Zn(s) is used to reduce other compounds in chemical reactions. If a chemist needs a substance that is more effective in its reducing ability, which of the following species would be the best choice? A. Na B. H+ C. K+ D. Cl−

A. Na

What is the maximum number of moles of Al2O3 that can be produced by the reaction of 0.40 mol of Al with 0.40 mol of O2 ? A.0.10 mol B. 0.20 mol C. 0.27 mol D. 0.33 mol E. 0.40 mol

B. 0.20 mol

Questions refer to three gases in identical rigid containers under the conditions given in the table below. The figure shows a table with 4 columns and 6 rows. The leftmost column contains the row labels, from top to bottom: row 1, Container; row 2, Gas; row 3, Formula; row 4, Molar mass (grams per mole); row 5, Temperature (degree Celsius); row 6, Pressure (standard atmosphere). From left to right, the data is as follows: Column 2; Container, A, Gas, Methane, Formula, C H 4, Molar mass, 16, Temperature, 27, Pressure, 2.0. Column 3; Container, B, Gas, Ethane, Formula, C 2 H 6, Molar mass, 30, Temperature, 27, Pressure, 4.0. Column 4; Container, C, Gas, Butane, Formula, C 4 H 10, Molar mass, 58, Temperature, 27, Pressure, 2.0. The density of the gas, in g/L, is A. greatest in container A B. greatest in container B C. greatest in container C D. the same in all three containers

B. greatest in container B

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel A. S B. Ca C. Ga D. Sb E. Br

C. Ga

Solid carbon tetrachloride, CCl4(s), is represented by the diagram above. The attractions between the CCl4 molecules that hold the molecules together in the solid state are best identified as A. polar covalent bonds B. nonpolar covalent bonds C. intermolecular attractions resulting from temporary dipoles D. intermolecular attractions resulting from permanent dipoles

C. intermolecular attractions resulting from temporary dipoles

Which of the following is the molecular formula of the unknown compound? A C4H8 B C4H8O C C4H4O2 D C4H8O2

C4H8O2

What number of moles of O2 is needed to produce 14.2 grams of P4O10 from P? (Molecular weight P4O10 = 284) A. 0.0500 mole B. 0.0625 mole C. 0.125 mole D. 0.250 mole E. 0.500 mole

D. 0.250 mole

Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid? A. NaF(aq)+HCl(aq)→NaCl(aq)+HF(aq) B. Na+(aq)+F−(aq)+H+(aq)+Cl−(aq)→Na+(aq)+Cl−(aq)+HF(aq) C. Na+(aq)+Cl−(aq)→NaCl(aq) D. F−(aq)+H+(aq)→HF(aq)

D. F−(aq)+H+(aq)→HF(aq)

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results? A. X has a larger molar mass than Y does. B. Y has a larger molar mass than X does. C. X is more polar than Y. D. Y is more polar than X.

D. Y is more polar than X.

At constant temperature, the behavior of a sample of a real gas more closely approximates that of an ideal gas as its volume is increased because the A. collisions with the walls of the container become less frequent B. average molecular speed decreases C. molecules have expanded D. average distance between molecules becomes greater E. average molecular kinetic energy decreases

D. average distance between molecules becomes greater

2 MnO4-(aq) + 10 Br-(aq) + 16 H+(aq) → 2 Mn2+(aq) + 5 Br2(aq) + 8 H2O(l) How many electrons are transferred in the reaction represented by the balanced equation above? A. 2 B. 4 C. 5 D. 8 E. 10

E. 10

A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask? A. 800 mm Hg B. 600 mm Hg C. 250 mm Hg D. 200 mm Hg E. 160 mm Hg

E. 160 mm Hg

Equal masses of He and Ne are placed in a sealed container. What is the partial pressure of He if the total pressure in the container is 6 atm? A. 1 atm B. 2 atm C. 3 atm D. 4 atm E. 5 atm

E. 5 atm

Of the following compounds, which is the most ionic? A. SiCl4 B. BrCl C. PCl3 D. Cl2O E. CaCl2

E. CaCl2

A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample? A. NaCl<KCl<KBr B. NaCl<KBr<KCl C. KCl<NaCl<KBr D. KBr<KCl<NaCl

D. KBr<KCl<NaCl

The table above 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

The ideal gas law best describes the properties of which of the following gases at 0°C and 1 atm? A. PH3 B. HBr C. SO2 D. N2

D. N2

The photoelectron spectra above show the energy required to remove a 1s electron from a nitrogen atom and from an oxygen atom. Which of the following statements best accounts for the peak in the upper spectrum being to the right of the peak in the lower spectrum? A. Nitrogen atoms have a half-filled p subshell. B. There are more electron-electron repulsions in oxygen atoms than in nitrogen atoms. C. Electrons in the p subshell of oxygen atoms provide more shielding than electrons in the p subshell of nitrogen atoms. D. Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

D. Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

Based on the information above and periodic trends, which of the following is the best hypothesis regarding the oxide(s) formed by Rb? A. Rb will form only Rb2O. B. Rb will form only Rb2O2. C. Rb will form only Rb2O and Rb2O2. D. Rb will form Rb2O, Rb2O2, and RbO2.

D. Rb will form Rb2O, Rb2O2, and RbO2.

2 SO2(g) + O2(g) → 2 SO3(g) A mixture of gases containing 0.20 mol of SO2 and 0.20 mol of O2 in a 4.0 L flask reacts to form SO3. If the temperature is 25ºC, what is the pressure in the flask after reaction is complete? A.0.4(0.082)(298) 4atm B. 0.3(0.082)(298) 4atm C 0.2(0.082)(298)4atm D 0.2(0.082)(25)4atm E 0.3(0.082)(25)4atm

B. 0.3(0.082)(298) 4atm

What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2? A. 9.85 g B. 19.7 g C. 24.5 g D. 39.4 g E. 48.9 g

B. 19.7 g

Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) The chemical equation shown above represents the reaction between Mg(s) and HCl(aq). When 12.15g of Mg(s) is added to 500.0mL of 4.0MHCl(aq), 95kJ of heat is released. The experiment is repeated with 24.30g of Mg(s) and 500.0mL of 4.0MHCl(aq). Which of the following gives the correct value for the amount of heat released by the reaction? A. 380kJ B. 190kJ C. 95kJ D. 48kJ

B. 190kJ

The chemical equation shown above represents the reaction between Mg(s) and HCl(aq). When 12.15g of Mg(s) is added to 500.0mL of 4.0MHCl(aq), 95kJ of heat is released. The experiment is repeated with 24.30g of Mg(s) and 500.0mL of 4.0MHCl(aq). Which of the following gives the correct value for the amount of heat released by the reaction? A. 380kJ B. 190kJ C. 95kJ D. 48kJ

B. 190kJ

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum? A. 1s22s22p1 B. 1s22s22p63s23p3 C. 1s22s22p63s23p6 D. 1s22s22p63s23p64s23d5

B. 1s22s22p63s23p3

The volume of water that must be added in order to dilute 40 mL of 9.0 M HCl to a concentration of 6.0 M is closest to A. 10 mL B. 20 mL C. 30 mL D. 40 mL E. 60 mL

B. 20 mL

A 2mol sample of F2(g) reacts with excess NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq) but with 1 mol of F2(g), which of the following is correct? A. The amount of OF2(g) produced is doubled. B. The amount of OF2(g) produced is halved. C. The amount of NaF(aq) produced remains the same. D. The amount of NaF(aq) produced is doubled.

B. The amount of OF2(g) produced is halved.

The elements C and Se have the same electronegativity value, 2.55. Which of the following claims about the compound that forms from C and Se is most likely to be true? A. The carbon-to-selenium bond is unstable. B. The carbon-to-selenium bond is nonpolar covalent. C. The compound has the empirical formula CSe. D. A molecule of the compound will have a partial negative charge on the carbon atom.

B. The carbon-to-selenium bond is nonpolar covalent.

C10H12O4S(s) + . . . O2(g) → . . . CO2(g) + . . . SO2(g) + . . . H2O(g) When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is A. 6 B. 7 C. 12 D. 14 E. 28

C. 12

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? A. 4.0 mol B. 8.0 mol C. 20. mol D. 24 mol

C. 20. mol

The complete photoelectron spectrum for an element is shown above. Which of the following observations would provide evidence that the spectrum is consistent with the atomic model of the element? A. A neutral atom of the element contains exactly two electrons. B. The element does not react with other elements to form compounds. C. In its compounds, the element tends to form ions with a charge of +1. D. In its compounds, the element tends to form ions with a charge of +3.

C. In its compounds, the element tends to form ions with a charge of +1.

To determine the moles of Fe3+(aq) in a 100. mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe3+(aq) into the dark red species FeSCN2+(aq), as represented by the equation above. The absorbance of FeSCN2+(aq) at different concentrations is shown in the graph below. The figure presents the graph in the first quadrant of a coordinate plane. The horizontal axis is labeled "Concentration of F e S C N with a positive 2 charge, in Molar," and the following three numbers are indicated: 0, 5 times 10 to the negative 5, and 10 times 10 to the negative 5, in increments of 1 times 10 to the negative 5. The vertical axis is labeled "Absorbance at 453 nanometers," and the numbers 0 through 0 points 5 0, in increments of 0 point 1 0, are indicated. The line of best fit is drawn. The line begins where the axes meet. It moves steadily upward and to the right passing through the point 5 times 10 to the negative 5 Molar and 0 point 2 5 absorbance. The line ends at 10 times 10 to the negative 5 Molar and 0 point 5 0 absorbance. There are 6 data points along the line. 1 point is at the origin, 3 points are above the line, and 2 points are below. If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe3+(aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN(s) is negligible.) A. 4 × 10−4 mol B. 3 × 10−4 mol C. 4 × 10−6 mol D. 3 × 10−6 mol

C. 4 × 10−6 mol

In 1.00 mol of potassium zirconium sulfate trihydrate, K4Zr(SO4)4 • 3 H2O, there are A. 3 × 6.02 × 1023 hydrogen atoms B. 6.02 × 1023 sulfur atoms C. 4 × 6.02 × 1023 potassium atoms D. 4 moles of oxygen atoms E. 4 moles of zirconium atoms

C. 4 × 6.02 × 1023 potassium atoms

A piece of Fe(s) at 25°C is placed into H2O(l) at 75°C in an insulated container. A student predicts that when thermal equilibrium is reached, the Fe atoms, being more massive than the H2O molecules, will have a higher average kinetic energy than the H2O molecules. Which of the following best explains why the student's prediction is incorrect? A. At thermal equilibrium, the less massive H2O molecules would have a higher average kinetic energy than the Fe atoms because they are more free to move than are the Fe atoms. B. At thermal equilibrium, the collisions between the Fe atoms and the H2O molecules would cease because the average kinetic energies of their particles would have become the same. C. At thermal equilibrium, the movement of both the Fe atoms and the H2O molecules would cease; thus, the average kinetic energy of their particles would have to be the same. D. At thermal equilibrium, the average kinetic energy of the Fe atoms cannot be greater than that of the H2O molecules; the average kinetic energies must be the same according to the definition of thermal equilibrium.

D. At thermal equilibrium, the average kinetic energy of the Fe atoms cannot be greater than that of the H2O molecules; the average kinetic energies must be the same according to the definition of thermal equilibrium.

The following questions refer to the below molecules: (A) CO2 (B) H2O (C) CH4 (D) C2H4 (E) PH3 The molecule with only one double bond A. CO2 B. H2O C. CH4 D. C2H4 E. PH3

D. C2H4

The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca2+ and Ar, are shown above. Which of the following correctly identifies the species associated with peak X and provides a valid justification? A. Ar, because it has completely filled energy levels B. Ar, because its radius is smaller than the radius of Ca2+ C. Ca2+, because its nuclear mass is greater than that of Ar D. Ca2+, because its nucleus has two more protons than the nucleus of Ar has

D. Ca2+, because its nucleus has two more protons than the nucleus of Ar has

RbCl has a high boiling point. Which of the following compounds is also likely to have a high boiling point, and why? A. NO, because its elements are in the same period of the periodic table. B. ClF, because its elements are in the same group of the periodic table. C. Cl2O, because its elements have similar electronegativities and it is a covalent compound. D. CsCl, because its elements have very different electronegativities and it is an ionic compound.

D. CsCl, because its elements have very different electronegativities and it is an ionic compound.

The question refers to the following species. (A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has two lone pairs of electrons A. H2O B. NH3 C. BH3 D. CH4 E. SiH4

A. H2O

NH4NO3(s) A 0.03 mol sample of NH4NO3(s) is placed in a 1 L evacuated flask, which is then sealed and heated. The NH4NO3(s) decomposes completely according to the balanced equation above. The total pressure in the flask measured at 400 K is closest to which of the following? (The value of the gas constant, R, is 0.082 L atm mol-1 K-1.) A. 3 atm B. 1 atm C. 0.5 atm D. 0.1 atm E. 0.03 atm

A. 3 atm

Table then graph given The temperature of the CH3OH is increased from 300 K to 400 K to vaporize all the liquid, which increases the pressure in the vessel to 0.30 atm. The experiment is repeated under identical conditions but this time using half the mass of CH3OH that was used originally. What will be the pressure in the vessel at 400 K ? A. 0.15 atm B. 0.30 atm C. 0.40 atm D. 0.60 atm

A. 0.15 atm

Gases W and X react in a closed, rigid vessel to form gases Y and Z according to the equation above. The initial pressure of W(g) is 1.20 atm and that of X(g) is 1.60 atm. No Y(g) or Z(g) is initially present. The experiment is carried out at constant temperature. What is the partial pressure of Z(g) when the partial pressure of W(g) has decreased to 1.0 atm? A. 0.20 atm B. 0.40 atm C. 1.0 atm D. 1.2 atm E. 1.4 atm

A. 0.20 atm

How many carbon atoms are contained in 2.8 g of C2H4 ? A. 1.2 x 1023 B. 3.0 x 1023 C. 6.0 x 1023 D. 1.2 x 1024 E. 6.0 x 1024

A. 1.2 x 1023

CS2(l) + 3 O2(g) → CO2(g) + 2 SO2(g) What volume of O2(g) is required to react with excess CS2(l) to produce 4.0 L of CO2(g)? (Assume all gases are measured at 0°C and 1 atm.) A. 12 L B. 22.4 L C. 13×22.4 L D. 2 × 22.4 L E. 3 × 22.4 L

A. 12 L

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.

Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains exactly two unpaired electrons A. S B. Ca C. Ga D. Sb E. Br

A. S

Which of the following statements, if true, would support the claim that the NO3− ion, represented above, 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.

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.

A balloon filled with 0.25 mol of He(g) at 273 K and 1 atm is allowed to rise through the atmosphere. Which of the following explains what happens to the volume of the balloon as it rises from ground level to an altitude where the air temperature is 220 K and the air pressure is 0.1 atm? A. The volume will increase because the decrease in air pressure will have a greater effect than the decrease in temperature. B. The volume will remain unchanged because of the counteracting effects of the decrease in temperature and the decrease in air pressure. C. The volume will decrease because the decrease in temperature will have a greater effect than the decrease in air pressure. D. It cannot be determined whether the volume of the balloon will increase, decrease, or remain the same without knowing the initial volume of the balloon.

A. The volume will increase because the decrease in air pressure will have a greater effect than the decrease in temperature.

The mass percent of carbon in pure glucose, C6H12O6, is 40.0 percent. A chemist analyzes an impure sample of glucose and determines that the mass percent of carbon is 38.2 percent. Which of the following impurities could account for the low mass percent of carbon in the sample? A. Water, H2O B. Ribose, C5H10O5 C. Fructose, C6H12O6, an isomer of glucose D. Sucrose, C12H22O11

A. Water, H2O

A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment? A. Which has the greater molar mass, X or Z ? B. Which has the higher boiling point, X or Z? C. Which has the higher melting point, XCl or ZCl? D. Which has the greater density, XCl or ZCl?

A. Which has the greater molar mass, X or Z ?

A student has two samples of NaCl, each one from a different source. Assume that the only potential contaminant in each sample is KCl. The student runs an experiment to determine the percent by mass of chlorine in each sample. From the results of this experiment alone, which of the following questions is most likely to be answered? A. Which sample has the higher purity? B. Which sample has the higher density? C. What is the source of the contaminants present in each of the samples? D. Which sample came from a salt mine, and which sample came from the ocean?

A. Which sample has the higher purity?

The table below contains information about samples of four different gases at 273 K. The samples are in four identical rigid containers numbered 1 through 4. The figure shows a table with 4 columns and 5 rows. The top row contains the column labels, from left to right: column 1, Container; column 2, Gas; column 3, Pressure (standard atmosphere); column 4, Mass of Sample (grams). From top to bottom, the data is as follows: Row 2; Container, 1, Gas, H e, Pressure, 2.00, Mass of Sample, ?. Row 3; Container, 2, Gas, N e, Pressure, 2.00, Mass of Sample, ?. Row 4; Container, 3, Gas, ?, Pressure, 2.00, Mass of Sample, 16.0. Row 5; Container, 3, Gas, S O 2, Pressure, 1.96, Mass of Sample, 64.1. Under the conditions given, consider containers 1, 2, and 4 only. The average speed of the gas particles is A. greatest in container 1 B. greatest in container 2 C. greatest in container 4 D. the same in containers 1, 2, and 4

A. greatest in container 1

A student wishes to prepare 2.00 liters of 0.100-molar KIO3 (molecular weight 214). The proper procedure is to weigh out A. 42.8 grams of KIO3 and add 2.00 kilograms of H2O B. 42.8 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters C. 21.4 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters D. 42.8 grams of KIO3 and add 2.00 liters of H2O E. 21.4 grams of KIO3 and add 2.00 liters of H2O

B. 42.8 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters

Approximately what mass of CuSO4 • 5H2O (250 g mol-1) is required to prepare 250 mL of 0.10 M copper(II) sulfate solution? A. 4.0 g B. 6.2 g C. 34 g D. 85 g E. 140 g

B. 6.2 g

The following questions refer to the 1 L flasks shown below. A diagram shows five flasks closed with a cork. Flask A contains N 2 gas at 30 degrees Celsius temperature and 1 a t m pressure. Flask B contains N 2 gas at 50 degrees Celsius temperature and 0.5 a t m pressure. Flask C contains O 2 gas at 40 degrees Celsius temperature and 2 a t m pressure. Flask D contains O 2 gas at 50 degrees Celsius temperature and 1 a t m pressure. Flask E contains O 2 gas at 40 degrees Celsius temperature and 0.5 a t m pressure. In which flask do the molecules have the greatest average speed? A. A B. B C. C D. D E. E

B. B

Equations given The proposed mechanism can be written in a more general form, as shown above. Species other than Cl can also decompose O3 through the same mechanism. Which of the following chemical species is most likely to decompose O3 in the upper atmosphere through the above mechanism? A. He B. Br C. N2 D. O2

B. Br

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 broken. D. Ionic bonds between H+ ions and OH- ions are broken. E. Covalent bonds between H+ ions and H2O molecules become more effective.

B. Hydrogen bonds between H2O molecules are broken.

The mass spectrum of a sample of a pure element is shown above. Based on the data, the peak at 26amu represents an isotope of which of the following elements? A. Al with 13 neutrons B. Mg with 14 neutrons C. Fe with 26 neutrons D. Ti with 26 neutrons

B. Mg with 14 neutrons

A 0.35 g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H2O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below A graph plots Base Added, in m L, on the horizontal axis, from 0.0 through 30.0, in increments of 10.0, and, p H on the vertical axis, from 0.0 through 14.0, in increments of 2.0. The graph plots a curve with an increasing trend that rises through the following estimated points: (0, 3.5), (10, 4.5), (20, 5.5), (25, 8), (30, 12), and (34, 12.4). What will be the effect on the amount of gas produced if the experiment is repeated using 0.35 g of K(s) instead of 0.35 g of Li(s) ? A. No gas will be produced when K(s) is used. B. Some gas will be produced but less than the amount of gas produced with Li(s). C. Equal quantities of gas will be produced with the two metals. D. More gas will be produced with K(s) than with Li(s).

B. Some gas will be produced but less than the amount of gas produced with Li(s).

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.

At 27°C, five identical rigid 2.0 L vessels are filled with N2(g) and sealed. Four of the five vessels also contain a 0.050 mol sample of NaHCO3(s), NaBr(s), Cu(s), or I2(s), as shown in the diagram above. The volume taken up by the solids is negligible, and the initial pressure of N2(g) in each vessel is 720 mm Hg. All four vessels are heated to 127°C and allowed to reach a constant pressure. At 127°C, the entire sample of I2 is observed to have vaporized. How does the mass of vessel 5 at 127°C compare to its mass at 27°C? A. The mass is less, since the I2 is in the vapor phase. B. The mass is the same, since the number of each type of atom in the vessel is constant. C. The mass is greater, since the I2 will react with N2 to form NI3 , which has a greater molar mass. D. The mass is greater, since the pressure is greater and the particles have a higher average kinetic energy.

B. The mass is the same, since the number of each type of atom in the vessel is constant.

A 2 L container will hold about 4 g of which of the following gases at 0°C and 1 atm? A. SO2 B. N2 C. CO2 D. C4H8 E. NH3

C. CO2

The diagram above represents a particle in aqueous solution. Which of the following statements about the particle is correct? A. The particle must be a cation because the negative end of each water molecule is pointed toward it. B. The particle must be an anion because the positive end of each water molecule is pointed toward it. C. The charge of the particle cannot be determined because water molecules have no net charge. D. The charge of the particle cannot be determined because the water molecules are arranged symmetrically and their partial charges cancel.

B. The particle must be an anion because the positive end of each water molecule is pointed toward it.

The reaction between NO(g) and O2(g) to produce NO2(g) in a rigid reaction vessel is represented in the diagram above. The pressure inside the container is recorded using a pressure gauge. Which of the following statements correctly predicts the change in pressure as the reaction goes to completion at constant temperature, and provides the correct explanation? A. The pressure will increase because the product molecules have a greater mass than either of the reactant molecules. B. The pressure will decrease because there are fewer molecules of product than of reactants. C. The pressure will decrease because the product molecules have a lower average speed than the reactant molecules. D. The pressure will not change because the total mass of the product molecules is the same as the total mass of the reactant molecules.

B. The pressure will decrease because there are fewer molecules of product than of reactants.

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.

A student prepares a solution by dissolving 60.00 g of glucose (molar mass 180.2 g mol-1) in enough distilled water to make 250.0 mL of solution. The molarity of the solution should be reported as A. 12.01 M B. 12.0 M C. 1.332 M D. 1.33 M E. 1.3 M

C. 1.332 M

At 27°C, five identical rigid 2.0 L vessels are filled with N2(g) and sealed. Four of the five vessels also contain a 0.050 mol sample of NaHCO3(s), NaBr(s), Cu(s), or I2(s), as shown in the diagram above. The volume taken up by the solids is negligible, and the initial pressure of N2(g) in each vessel is 720 mm Hg. All four vessels are heated to 127°C and allowed to reach a constant pressure. At 127°C, the pressure in vessel 1 is found to be higher than that in vessel 2. Which of the following reactions best accounts for the observation? A. NaHCO3(s) → Na(s) + HCO3(s) B. NaHCO3(s) → NaH(s) + CO3(s) C. 2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) D. 2 NaHCO3(s) + N2(g) → 2 NaNO3(s) + C2H2(g)

C. 2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)

The diagram above 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 . Which of the following is closest to the frequency of the light with photon energy of 3.3×10−19J? A. 5.0×10−53s−1 B. 5.0×10−16s−1 C. 5.0×1014s−1 D. 5.0×1052s−1

C. 5.0×1014s−1

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 1.0atm. 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.

Which of the following is the most likely cause for the increase in pressure observed in the container as the reaction reaches equilibrium? A. A decrease in the strength of intermolecular attractions among molecules in the flask B. An increase in the strength of intermolecular attractions among molecules in the flask C. An increase in the number of molecules, which increases the frequency of collisions with the walls of the container D. An increase in the speed of the molecules that then collide with the walls of the container with greater force

C. An increase in the number of molecules, which increases the frequency of collisions with the walls of the container

The question refers to the following species. (A) H2O (B) NH3 (C) BH3 (D) CH4 (E) SiH4 Has a central atom with less than an octet of electrons A. H2O B. NH3 C. BH3 D. CH4 E. SiH4

C. BH3

The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of the periodic properties, which of the following compounds can most likely be used as a fire-resistant chemical? A. BCl3 B. CH4 C. CBr4 D. PbCl2

C. CBr4

To make Au stronger and harder, it is often alloyed with other metals, such as Cu and Ag. Consider two alloys, one of Au and Cu and one of Au and Ag, each with the same mole fraction of Au. If the Au/Cu alloy is harder than the Au/Ag alloy, then which of the following is the best explanation based on the information in the table above? A. Cu has two common oxidation states, but Ag has only one. B. Cu has a higher melting point than Au has, but Ag has a lower melting point than Au has. C. Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy. D. Cu atoms are less polarizable than are Au or Ag atoms, thus Cu has weaker interparticle forces.

C. Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy.

Refer to the following diatomic species (A) Li2 (B) B2 (C) N2 (D) O2 (E) F2 Has the largest bond-dissociation energy A. Li2 B. B2 C. N2 D. O2 E. F2

C. N2

The volume of a sample of air in a cylinder with a movable piston is 2.0 L at a pressure P1, as shown in the diagram above. The volume is increased to 5.0 L as the temperature is held constant. The pressure of the air in the cylinder is now P2. What effect do the volume and pressure changes have on the average kinetic energy of the molecules in the sample? A. The average kinetic energy increases. B. The average kinetic energy decreases. C. The average kinetic energy stays the same. D. It cannot be determined how the kinetic energy is affected without knowing P1 and P2.

C. The average kinetic energy stays the same.

A 1.0 L sample of a pure gas is found to have a lower pressure than that predicted by the ideal gas law. The best explanation for the observation is that the molecules of the gas A. have a combined volume that is too large to be considered negligible when compared to the volume of the container B. have a low molecular mass and therefore do not strike the container walls with as much force as expected C. are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions D. are attracted to the sides of the container and strike the container walls with more force than expected

C. are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions

The table below contains information about samples of four different gases at 273 K. The samples are in four identical rigid containers numbered 1 through 4. The figure shows a table with 4 columns and 5 rows. The top row contains the column labels, from left to right: column 1, Container; column 2, Gas; column 3, Pressure (standard atmosphere); column 4, Mass of Sample (grams). From top to bottom, the data is as follows: Row 2; Container, 1, Gas, H e, Pressure, 2.00, Mass of Sample, ?. Row 3; Container, 2, Gas, N e, Pressure, 2.00, Mass of Sample, ?. Row 4; Container, 3, Gas, ?, Pressure, 2.00, Mass of Sample, 16.0. Row 5; Container, 3, Gas, S O 2, Pressure, 1.96, Mass of Sample, 64.1. The best explanation for the lower pressure in container 4 is that SO2 molecules A. have a larger average speed than the other three gases B. occupy a larger portion of the container volume than the other three gases C. have stronger intermolecular attractions than the other three gases D. containπbonds, while the other gases contain onlyσbonds

C. have stronger intermolecular attractions than the other three gases

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution? A. 0.0800 M B. 0.0400 M C. 0.0200 M D. 0.0100 M E. 0.00250 M

D. 0.0100 M

What is the molarity of I-(aq) in a solution that contains 34 g of SrI2 (molar mass 341 g) in 1.0 L of the solution? A. 0.034 M B. 0.068 M C. 0.10 M D. 0.20 M E. 0.68 M

D. 0.20 M

A solution of methanol, CH3OH, in water is prepared by mixing together 128 g of methanol and 108 g of water. The mole fraction of methanol in the solution is closest to A. 0.80 B. 0.60 C. 0.50 D. 0.40 E. 0.20

D. 0.40

For an experiment, a student needs 100.0 mL of 0.4220 M NaCl. If the student starts with NaCl(s) and distilled water, which of the following pieces of laboratory glassware should the student use to prepare the solution with the greatest accuracy? A. 25 mL volumetric pipet B. 100 mL Erlenmeyer flask C. 100 mL graduated cylinder D. 100 mL volumetric flask E. 1 L beaker

D. 100 mL volumetric flask

How many mL of 10.0 M HCl are needed to prepare 500. mL of 2.00 M HCl ? A. 1.00 mL B. 10.0 mL C. 20.0 mL D. 100. mL E. 200. mL

D. 100. mL

The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a 0.500 M HCl(aq) solution is approximately A. 50.0 mL B. 60.0 mL C. 100. ML D. 110. ML E. 120. mL

D. 110. ML

Given that the density of Hg(l) at 0°C is about 14 g mL-1, which of the following is closest to the volume of one mole of Hg(l) at this temperature? A. 0.070 mL B. 0.14 mL C. 1.4 mL D. 14 mL E. 28 mL

D. 14 mL

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.

C H 3 O H gas reacts to form C O gas plus 2 H 2 gas. Delta H naught equals positive 91 kilojoules per mole of reaction. The reaction represented above goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K A sample of CH3OH(g) is placed in the previously evacuated vessel with a pressure of P1 at 600 K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600 K? A. P1 / 9 B. P1 / 3 C. P1 D. 3P1

D. 3P1

When 70. milliliter of 3.0-molar Na2CO3 is added to 30. milliliters of 1.0-molar NaHCO3 the resulting concentration of Na+ is A. 2.0 M B. 2.4 M C. 4.0 M D. 4.5 M E. 7.0 M

D. 4.5 M

A student obtains a mixture of the liquids hexane and octane, which are miscible in all proportions. Which of the following techniques would be best for separating the two components of the mixture, and why? A. Filtration, because the different densities of the liquids would allow one to pass through the filter paper while the other would not. B. Paper chromatography, because the liquids would move along the stationary phase at different rates owing to the difference in polarity of their molecules. C. Column chromatography, because the higher molar mass of octane would cause it to move down the column faster than hexane. D. Distillation, because the liquids would boil at different temperatures owing to the difference in strength of their intermolecular forces.

D. Distillation, because the liquids would boil at different temperatures owing to the difference in strength of their intermolecular forces.

Questions refer to three gases in identical rigid containers under the conditions given in the table below. The figure shows a table with 4 columns and 6 rows. The leftmost column contains the row labels, from top to bottom: row 1, Container; row 2, Gas; row 3, Formula; row 4, Molar mass (grams per mole); row 5, Temperature (degree Celsius); row 6, Pressure (standard atmosphere). From left to right, the data is as follows: Column 2; Container, A, Gas, Methane, Formula, C H 4, Molar mass, 16, Temperature, 27, Pressure, 2.0. Column 3; Container, B, Gas, Ethane, Formula, C 2 H 6, Molar mass, 30, Temperature, 27, Pressure, 4.0. Column 4; Container, C, Gas, Butane, Formula, C 4 H 10, Molar mass, 58, Temperature, 27, Pressure, 2.0. The average kinetic energy of the gas molecules is A. greatest in container A B. greatest in container B C. greatest in container C D. the same in all three containers

D. the same in all three containers

Which of the following techniques is most appropriate for the recovery of solid KNO3 from an aqueous solution of KNO3? A. Paper chromatography B. Filtration C. Titration D. Electrolysis E. Evaporation to dryness

E. Evaporation to dryness