Practice MC 41-60

N₂ molecules absorb ultraviolet light but not visible light. I₂ molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations?

• More energy is required to make N₂ molecules vibrate than is required to make I₂ molecules vibrate.

• More energy is required to remove an electron from an I₂ molecule than is required to remove an electron from a N₂ molecule.

• Visible light does not produce transitions between electronic energy levels in the N₂ molecule but does produce transitions in the

  I₂ molecule.

• The molecular mass of I₂ is greater than the molecular mass of N₂ .

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?

• Cu has two common oxidation states, but Ag has only one.

• Cu has a higher melting point than Au has, but Ag has a lower melting point than Au has.

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

• Cu atoms are less polarizable than are Au or Ag atoms, thus Cu has weaker interparticle forces.

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?

• Nitrogen atoms have a half-filled p subshell.

• There are more electron-electron repulsions in oxygen atoms than in nitrogen atoms.

• Electrons in the p subshell of oxygen atoms provide more shielding than electrons in the p subshell of nitrogen atoms.

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

Nonane and 2,3,4-trifluoropentane have almost identical molar masses, but nonane has a significantly higher boiling point. Which of the following statements best helps explain this observation?

• The C–F bond is easier to break than the C–H bond.

• The C–F bond is more polar than the C–H bond.

• The carbon chains are longer in nonane than they are in 2,3,4- trifluoropentane.

• The carbon chains are farther apart in a sample of nonane than they are in 2,3,4-trifluoropentane.

Half-cell 1: strip of Al(s) in 1.00 M Al(NO₃)₃(aq)

Half-cell 2: strip of Cu(s) in 1.00 M Cu(NO₃)₂(aq)

Half-cell 3: strip of Fe(s) in 1.00 M Fe(NO₃)₂(aq)

What is the standard cell potential of galvanic cell Z?

• 0.26 V

• 0.78 V

• 2.34 V

• 3.22 V

Half-cell 1: strip of Al(s) in 1.00 M Al(NO₃)₃(aq)

Half-cell 2: strip of Cu(s) in 1.00 M Cu(NO₃)₂(aq)

Half-cell 3: strip of Fe(s) in 1.00 M Fe(NO₃)₂(aq)

In galvanic cells Y and Z, which of the following takes place in half-cell 3 ?

• Reduction occurs in both cell Y and cell Z.

• Oxidation occurs in both cell Y and cell Z.

• Reduction occurs in cell Y, and oxidation occurs in cell Z.

• Oxidation occurs in cell Y, and reduction occurs in cell Z.

Half-cell 1: strip of Al(s) in 1.00 M Al(NO₃)₃(aq)

Half-cell 2: strip of Cu(s) in 1.00 M Cu(NO₃)₂(aq)

Half-cell 3: strip of Fe(s) in 1.00 M Fe(NO₃)₂(aq)

If the half-cell containing 1.00 M Fe(NO₃)₂(aq) in galvanic cells Y and Z is replaced with a half-cell containing 5.00 M Fe(NO₃)₂(aq), what will be the effect on the cell voltage of the two galvanic cells?

• The voltage will increase in both cells.

• The voltage will decrease in both cells.

• The voltage will increase in cell Y and decrease in cell Z.

• The voltage will decrease in cell Y and increase in cell Z.

The pH of solutions of four acids prepared at various concentrations were measured and recorded in the table above. The four acids are, in no particular order, chlorous, hydrochloric, lactic, and propanoic.

For which acid is the value of the acid dissociation constant, Ka, the smallest?

• Acid 1

• Acid 2

• Acid 3

• Acid 4

The pH of solutions of four acids prepared at various concentrations were measured and recorded in the table above. The four acids are, in no particular order, chlorous, hydrochloric, lactic, and propanoic.

Which of the four acids listed in the table is hydrochloric acid?

• Acid 1

• Acid 2

• Acid 3

• Acid 4

The pH of solutions of four acids prepared at various concentrations were measured and recorded in the table above. The four acids are, in no particular order, chlorous, hydrochloric, lactic, and propanoic.

Of the following species, which has the greatest concentration in a 1.0 M solution of acid 1 at equilibrium?

• OH⁻

• H₃O⁺

• Acid 1

• The conjugate base of acid 1