CHAPTER 12

Question 1

Which statement best describes the rate of a reaction?

The change in concentration of reactants or products per unit mass.

The change in concentration (moles/L) of reactants or products per unit time.

The change in moles of reactants or products per unit time.

The change in concentration of reactants or products per mole.

Answer 1

The change in concentration (moles/L) of reactants or products per unit time.

Question 2

The decomposition of hydrogen peroxide, H2O2 is described by the equation:

2 H2O2 → 2 H2O + O2

The rate of decomposition of H2O2 at time point (t) = - 4 x 10 -4 M h-1

We can say that the rate of formation of H2O and O2 at time point (t) is respectively:

• 4 x 10 -4 M h-1 and - 2 x 10 -4 M h-1

2 x 10 -4 M h-1 and 4 x 10 -4 M h-1

• 2 x 10 -4 M h-1 and - 4 x 10 -4 M h-1

4 x 10 -4 M h-1 and 2 x 10 -4 M h-1

Answer 2

4 x 10 -4 M h-1 and 2 x 10 -4 M h-1

Question 3

In the nuclear industry, chlorine trifluoride is used to prepare uranium hexafluoride. Chlorine trifluoride is prepared by the reaction:

Cl2 (g) + 3 F2 (g) → 2 ClF3 (g)

The rate expression coefficients would be for Cl2, F2, ClF3 respectively:

+1, +1/3, -1/2

1, -1/3, +1/2

• 1, -1/3, +1/2
• 1, -1/3, -1/2

Answer 3

-1, -1/3, +1/2

Question 4

For a reaction to proceed from reactants to products, reactants must collide with:

sufficient energy to overcome the activation energy only.

sufficient energy to overcome the activation energy and in the correct orientation.

some of the proto-products in order for an occlusion of the spin states to orientate.

sufficient time and in the correct orientation.

Answer 4

sufficient energy to overcome the activation energy and in the correct orientation.

Question 5

Increasing the temperature of a reaction will increase what characteristics of the reactants?

velocity and kinetic energy

none of these

proportion of correct collision orientations and kinetic energy

activation energy and kinetic energy

Answer 5

velocity and kinetic energy

Question 6

According to an activation energy diagram, the major determinant of whether a reaction proceeds through the transition state from reactants to products is:

enthalpic activation energy vectors.

the activation energy.

the difference in energy between reactants and products.

enthalpy.

Answer 6

the activation energy.

Question 7

The energy of the transition state would equal which of the following functions:

∆ H + C +D

(energy of reactants) - (energy of products)

(energy of reactants) + Ea

(energy of reactants) + (energy of products)

Answer 7

(energy of reactants) + Ea

Question 8

Chemical reactions occur when reactants collide. What factors may prevent a collision from producing a chemical reaction?

Insufficient kinetic energy to exceed the activation energy and incorrect orientation

The reaction does produce heat and sufficient kinetic energy to exceed the activation energy.

The reaction does not produce heat and insufficient kinetic energy to exceed the activation energy.

none of these

Answer 8

Insufficient kinetic energy to exceed the activation energy and incorrect orientation

Question 9

Approximately how much faster would a reaction proceed at 45 oC compared to 25 oC?

0.56 times

two times

1.8 times

four times

Answer 9

four times

Question 10

TNT (trinitrotoluene) reacts much more violently than old-fashioned black powder, though TNT requires a detonator to produce an explosion. From this observation, we can conclude:

TNT reacts more quickly because this reaction is more exothermic than the black powder reaction, and TNT has a very high activation energy compared to black powder.

TNT reacts more quickly because the reactants are in closer proximity compared to black powder, and TNT has a very high activation energy.

TNT reacts more quickly because the reactants are in closer proximity compared to black powder, and TNT has a very low activation energy compared to black powder.

TNT is much more unstable than black powder and subject to detonation by subtle movement.

Answer 10

TNT reacts more quickly because the reactants are in closer proximity compared to black powder, and TNT has a very high activation energy.

Question 11

Consider this reaction:

NO2 (g) + CO (g) →CO2 (g) + NO (g)

The reaction mechanism for the above reaction is:

NO2 (g) + NO2 (g) →NO3 (g) + NO (g) (slow)
NO3 (g) + CO (g) → NO2 (g) + CO2 (g) (fast)

From this information, we can conclude that the rate of the reaction is proportional to only:

NO2 and CO

NO3 and CO

NO2, NO3 and CO

NO2

Answer 11

NO2