ap chem midterm - units 1-4

A 0.50 g sample of Mg (s) was placed in a solution of HCl (aq), where it is reacted completely. Which of the following equations best represents the reacting species in the reaction described above?

A.) Mg (s) + 2H⁺ (aq) → Mg²⁺ (aq) + H₂ (g)

Equal volumes of 0.2M solutions of Lead (II) Nitrate and Potassium Bromide are combined to form Lead (II) Bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?

A.) Pb²⁺ (aq) + 2Br⁻ (aq) → PbBr₂ (s)

If 50. mL of 1.0 NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resolution solution is

0.025 M

Initial buret reading: 2.17 mL Final buret reading: 22.17 mL An antacid tablet containing Mg(OH)₂ (s) (molar mass 58.3 g/mol) is titrated with 1.000M solution of HNO₃ (aq). The end point is determined by using an indicator. Based on the data in the table above, what was the mass of the Mg(OH)₂ (s) in the antacid tablet?

0.583 g

A sealed vessel contains .200 mol of oxygen gas, .100 mol of nitrogen gas, and .200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the nitrogen is...

1.00 atm

how many carbon atoms are contained in 2.8g of C₂H₄

1.2 x 10^23

2Al (s) + 6HCl (aq) → 2AlCl₃ (aq) + 3H₂ (g). According to the reaction represented above, about how many grams of aluminum (atomic mass 27g) are necessary to produce 1.00 mol of hydrogen gas at 25 degrees Celcius and 1.00 atm?

18 g

The complete photoelectron spectrum of an element is given above. Which of the following electron configurations is consistent with the spectrum to the right?

1s²2s²2p⁶3s²3p³

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?

2

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, which of the following identifies the oxidation and reduction half-reactions?

2nd choice/B

A 2L sample of N₂ (g) and a 1 L sample of Ar (g), each originally at 1 atm and 0 degrees Celcius, are combined in a 1 L tank. If the temperature is held constant, what is the total pressure of the gases in the tank?

3 atm

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 solution at a wavelength of 510 nm and constructs a standard curve. Finally, the student determines the absorbance of the sample of unknown concentration. A wavelength of 510 nm corresponds to an approximate frequency of 6 x 10¹⁴ s^-1. What is the approximate energy of one photon of this light.

4 x 10⁻¹⁹ J

C₃H₈ (g) + 5O₂ (g) → 3CO₂ (g) + 4H₂O (l) In the reaction represented above, what is the total number of moles of reactants consumed when 3.00 moles of CO₂ (g) is produced?

6.00 mol

2N₂H₄ (g) + N₂O₄ (g) → 3N₂ (g) + 4H₂O (g). When 8.0 g of N₂H₄ (32g/mol) and 92g of N₂O₄ (92g/mol) are mixed together and react according to the equation above, what is the maximum mass of H₂O that can be produced?

9.0 g

Steel is an alloy containing Fe and C atoms. Which of the following diagrams best represents the particle-level structure of steel?

A

Which flask do the molecules have the lowest average speed?

A

Which of the following best shows the speed distribution of He (g) atoms under the same conditions of the temperature and pressure? (Solid line is H₂, dotted line is He)

A

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

A precipitation reaction:

B.) Pb²⁺ (aq) + CrO₄²⁻ (aq) → PbCrO₄ (s)

This compound has a central atom with less than an octet of electrons.

BBr₃

The structural formula of the glycinium cation is shown to the left. Arrows indicate the pKa values for the liable protons in the molecule. What is the approximate H-O-C bond angle in the glycinium cation? What is the shape?

Bent, 105 degrees

This compound has exactly 2 sigma and 2 pi bonds.

CS₂

This compound is predicted to have the largest bond angle.

CS₂

Which of the following is a nonpolar molecule that contains polar bonds?

CS₂

Which of the following substances has bonds with the greatest ionic character?

CaCl₂

The four below (Cl-, Ar, K+, Ca2+) all have the same electron configuration, 1s²2s²2p⁶3s²3p⁶. Which of the following statements correctly identifies the species with the largest radius and provides an explanation based on Coulomb's Law?

Cl-, because its nuclear charge exerts the least attractive force on the electrons in the 3p sublevel.

Which is the empirical formula of an oxide of chromium that has 48% oxygen by mass?

CrO₃

Which has the largest atomic radius?

Cs

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

D.) 2Ag⁺ (aq) + Ni (s) → 2Ag (s) + Ni²⁺ (aq)

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?

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

An oxidation-reduction reaction that is also a synthesis reaction

D.) 2Mg (s) + O₂ (g) → 2MgO (s)

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

D.) Sr²⁺ (aq) + SO₄²⁻ (aq) → SrSO₄ (s)

Which of the following has the bonds arranged in order of decreasing polarity?

H-F > N-F > F-F

Of the following molecules, which has the largest dipole moment?

HCl

Which of the following describes the changes in forces of attraction that occur as H₂O changes phase from a solid to a liquid?

Hydrogen bonds between H₂O molecules are broken.

Which of the following techniques would be best to investigate molecular vibrations in molecules of red food dye?

Infrared spectroscopy

The element Iodine and Tellurium have similar average atomic masses. A sample that was believed to be a mixture of Iodine and Tellurium was run through a mass spectrometer, resulting in the data shown below. All of the following statements are true. Which one would be the best basis for concluding that the sample was pure Tellurium?

Iodine consists of only one naturally occurring isotope with 74 neutrons, whereas Te has more than one isotope.

Based on the results of the paper chromatography experiment shown, which of the following can be concluded about the dye?

It has a weaker attraction for the stationary phase than it has for the mobile phase.

Cu (s) + 4HNO₃ (aq) → Cu(NO₃)₂ (aq) + 2NO₂ (g) + 2H₂O (l). Each student in a class placed 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 15.8M 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.

It is a redox reaction, because Cu(s) is oxidized and the Nitrogen atom in NO₃⁻ (aq) is reduced.

A compound contains 1.10 mol of K, 0.55 mol of Te, and 1.65 mol of O. What is the simplest formula of this compound?

K₂TeO₃

A sample of unknown gas from a cylinder is collected over water in the apparatus shown. 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

Mass of the water in the apparatus

according to the information in the table to the left, 1.00. g of which of the following contains the greatest mass of Oxygen?

MgO

1s²2s²2p⁶3s²3p⁴ atoms of an element, X, have the electronic configuration shown to the left. The compound most likely formed with magnesium, Mg, is...

MgX

A student obtains a sample of pure solid compound. In addition to Avagadro's number, which of the following must the student know in order to determine how many molecules are in the sample?

Molar mass of the compound, mass of the sample

This compound has a central atom with only one set of lone pair electrons.

NF₃

This compound is expected to have a pyramidal structure.

NF₃

On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?

NH₃

Which of the following compounds contains both ionic and covalent bonds?

NH₄F

The photoelectron spectra above shows 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 right spectrum being to the right of the speak in the lower spectrum?

Nitrogen atoms have a smaller nuclear charge than oxygen atoms.

Which of the following particulate diagrams best represents the products when four molecules of H₂O₂ (l) decompose into water and oxygen gas at room temperature?

Option 4

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. The reaction is correctly classified as which of the following types?

Oxidation-reduction, because I₂ is reduced.

Equal number of moles of He (g), Ar (g), and Ne (g) are placed in a glass vessel at room temperature. If the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressure of the gases remaining in the vessel after some of the gas mixture has effused?

Pₕₑ < Pₙₑ < Pₐᵣ

Which of the following gases deviates most from ideal behavior?

SO₂

In which of the following species does sulfur have the same oxidation number as it does in H₂SO₄?

SO₂Cl₂

For which of the following molecules are resonance structures necessary to describe the bonding satisfactorily?

SeS₂

CCl₄ (g) deviates more from the ideal gas behavior than CH₄ (g) does. Which of the following statements best explains this observation?

The London dispersion forces between CCl₄ molecules are stronger than those between CH₄

Which of the following statements, if true, would support the claim that NO₃⁻ ion, represented to the left, has three resonance structures?

The NO₃⁻ ion is not a polar species

The table to the left provides some information about the two types of steel, both of which are alloys of iron and carbon. Which of the following best helps explain why high-carbon steel (hard and brittle) is more rigid than low-carbon steel (malleable and ductile)?

The addition of the carbon atoms within the alloy make it more difficult for the iron atoms to slide past one another.

The diagram shows the distribution of molecular speed in a sample of gas at two different temperatures, T₁ and T₂. Which of the following is a correct interpretation of the information provided by the diagram?

The average kinetic energy of the molecules is greater at T₂ than at T₁

The table to the left shows the melting points of MgO (s) (2852 C) and NaF (s) (993 C). Which of the following best helps explain why the melting point of MgO (s) is much higher than that of NaF (s)?

The charges of Mg²⁺ and O²⁻ ions are greater than those of Na⁺ and F⁻ ions.

A student placed a sample of food coloring that contains a mixture of blue dye and red dye at the top of the chromatography column filled with a nonpolar stationary phase. When the water is poured through the column, two bands of colors are seen in the column, as shown in the diagram. Which of the following will most likely be observed if CH₃OH (l) is used in the column instead of water.

The dyes will pass through the column at a slower rate because CH₃OH (l) is a less polar solvent than water.

An ionic crystal is added to water and starts to dissolve as shown in the particulate representation. Based on the orientation of the water molecules, what can be assumed about the charge of the hydrated particle indicated by the arrow?

The particle is positively charged, because the oxygen atoms in the water are attracted to it.

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?

The resulting solution conducts electricity.

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 will happen to the volume of the balloon as it rises from the ground level to an altitude where the air temperature is 220 K and the air pressure is 0.1 atm?

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

Which of the following is the best piece of laboratory glassware for preparing 500.0 mL of aqueous solution of a solid?

Volumetric Flask

Which of the following best helps explain why the electronegativity of Cl is less than that if F?

When Cl and F forms bonds with other atoms, the Cl bonding electrons are more shielded from the positive Cl nucleus than the F bonding electrons are shielded from the positive F nucleus.

A student has a sample 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?

Which has the greater molar mass, X or Z?

The ionization energies of an unknown element are listed below. Which of the following is most likely the empirical formula of a compound formed from element X and phosphorus, P?

X₃P₂

The mass spectrum of an average sample of a pure element is shown in the figure below. Which of the following is the identity of the element?

Zr

At standard temperature and pressure, a .50 mol sample of H₂ gas and a seperate 1.0 mol sample of O₂ gas have the same...

average molecular kinetic energy

According to the VSEPR model, the progressive decrease in bond angle in the series of molecules CH₄, NH₃, and H₂O is best accounted for by the...

increasing number of unshared pairs of electrons

What is the hybridization of the carbon atoms in a molecule of ethene?

sp²

Of the following diagrams, which best represents the structure of solid CsCl?

B

Which flask contains the larges number of moles of gas?

C

Which flask contains the sample with the greatest density?

C