Practice MC 1-20

Complete combustion of a sample of a hydrocarbon in excess oxygen produces equimolar quantities of carbon dioxide and water. Which of the following could be the molecular formula of the compound?

• C₂H₂

• C₂H₆

• C₄H₈

• C₆H₆

Based on the data in the table above, which of

the following liquid substances has the weakest

intermolecular forces?

• C₆H₆(l)

• C₂H₅OH(l)

• CH₃OH(l)

• C₂H₆O₂(l)

Based on the data in the table above, which of the

following correctly predicts the relative strength

of the attraction of Zn²⁺, Ca²⁺, and Ba²⁺ ions to

water molecules in a solution, from strongest to

weakest, and provides the correct reason?

• Zn²⁺ > Ca²⁺ > Ba²⁺ because the smaller ions have a stronger coulombic attraction to water

• Zn²⁺ > Ca²⁺ > Ba²⁺ because the smaller ions are more electronegative

• Ba²⁺ > Ca²⁺ > Zn²⁺ because the larger ions are more polarizable

• Ba²⁺ > Ca²⁺ > Zn²⁺ because the larger ions are less electronegative

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?

• Na

• H+

• K+

• Cl−

In the diagram above, which of the labeled arrows

identifies hydrogen bonding in water?

• A

• B

• C

• D

A kinetics experiment is set up to collect the gas that is generated when a sample of chalk, consisting primarily of solid CaCO₃ , is added to a solution of ethanoic acid, CH₃COOH. The rate of reaction between CaCO₃ and CH₃COOH is determined by measuring the volume of gas

generated at 25^oC and 1 atm as a function of time. Which of the following experimental conditions is most likely to increase the rate of gas production?

• Decreasing the volume of ethanoic acid solution used in the experiment

• Decreasing the concentration of the ethanoic acid solution used in the experiment

• Decreasing the temperature at which the experiment is performed

• Decreasing the particle size of the CaCO₃ by grinding it into a fine powder

H₂(g) + I₂(g) → 2 HI(g)

At 450^oC, 2.0 moles each of H₂(g), I₂(g), and HI(g) are combined in a 1.0 L rigid container. The value of Kc at 450^oC is 50. Which of the following will occur as the system moves toward equilibrium?

• More H₂(g) and I₂(g) will form.

• More HI(g) will form.

• The total pressure will decrease.

• No net reaction will occur, because the number of molecules is the same on both sides of the equation.

The graph above shows the speed distribution of molecules in a sample of a gas at a certain temperature. Which of the following graphs shows the speed distribution of the same

molecules at a lower temperature (as a dashed curve) ?

• 
• 
• 
• 

A 100 g sample of a metal was heated to 100^oC and then quickly transferred to an insulated container holding 100 g of water at 22^oC. The temperature of the water rose to reach a final temperature of 35^oC. Which of the following can be concluded?

• The metal temperature changed more than the water temperature did; therefore the metal lost more thermal energy than the water

  gained.

• The metal temperature changed more than the water temperature did, but the metal lost the same amount of thermal energy as the water gained.

• The metal temperature changed more than the water temperature did; therefore the heat capacity of the metal must be greater than

  the heat capacity of the water.

• The final temperature is less than the average starting temperature of the metal and the water; therefore the total energy of the metal and water decreased.

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

• Te forms ions with a −2 charge, whereas I forms ions with a −1 charge.

• Te is more abundant than I in the universe.

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

• I has a higher first ionization energy than Te does.