Question 1

A chemical reaction is observed to proceed much faster when the reactants are in powdered form rather than in large chunks. Which factor is primarily responsible for this increase in reaction rate?

Accepted Answer

The increased surface area of the powdered reactants allows for more frequent collisions.

Question 2

For the reaction $$2A + B + 4C \rightarrow D$$, experimental data shows that doubling $$[A]$$ doubles the rate, doubling $$[B]$$ has no effect, and doubling $$[C]$$ quadruples the rate. What is the correct rate law for this reaction?

Accepted Answer

Rate = k[A][C]^2

Question 3

Which of the following statements best explains why coal dust is explosive while lump charcoal is not?

Accepted Answer

Coal dust has a much greater surface area, leading to more frequent collisions and a faster reaction rate.

Question 4

A reaction is found to be first order with respect to $$A. $$Which of the following plots will yield a straight line?

Accepted Answer

$$\ln[A] vs$$. $$t$$

Question 5

The half-life of a first-order reaction is given by $$t_{1/2} = \frac{0.693}{k}. If $$the rate constant $$k$$ for a radioactive isotope is $$0.0866$$ days$$^{-1}$$, what is its half-life?

Accepted Answer

8.01 days

Question 6

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It lowers the activation energy, providing an alternative pathway for the reaction.

Question 7

For the reaction $$3H_2 + N_2$ \rightarrow 2NH_3$$, if $$H_2$$ disappears at a rate of $$3.0 M/s$$, what is the rate of appearance of $$NH_3$$?

Accepted Answer

2.0 M/s

Question 8

A reaction mechanism consists of the following steps:
1. $$A + A \rightarrow A_2$ (fast)
2. A_2$ + B \rightarrow A_2B ($$slow)
3. $$A_2B + B \rightarrow A_2B_2 ($$fast)
What is the rate law for the overall reaction?

Accepted Answer

Rate = k[A]^2[B]

Question 9

Which of the following is true about the rate constant $$k in a $$rate law?

Accepted Answer

It is temperature dependent and its units depend on the overall order of the reaction.

Question 10

A Maxwell-Boltzmann distribution curve for a reaction shows that increasing the temperature will:

Accepted Answer

Increase the fraction of molecules with energy greater than the activation energy.

Question 11

Which of the following statements about reaction intermediates is correct?

Accepted Answer

They are produced in one step and consumed in another, and do not appear in the overall reaction.

Question 12

The rate law for a reaction is found to be $$	ext{Rate} = k[A]^2[B]. $$What are the units of the rate constant $$k$$?

Accepted Answer

$$\mathrm{M}^{-1}\mathrm{s}^{-1}$$

Question 13

Which of the following best describes the rate-determining step in a multistep reaction mechanism?

Accepted Answer

It is the slowest step with the highest activation energy.

Question 14

A catalyst is added to a reaction. Which of the following changes would you expect to observe in the reaction energy profile?

Accepted Answer

The activation energy ($$E_a) is $$lower for the catalyzed pathway.

Question 15

Which of the following is a correct statement about the role of a catalyst in a reaction mechanism?

Accepted Answer

A catalyst is consumed in the rate-determining step and regenerated in a subsequent step.

Question 16

The reaction $$2O_3 \rightarrow 3O_2$$ proceeds via the following steps:
1. $$O_3$$ + $$O_3$$ \rightarrow $$O_3$$ + $$O_2 + O$
2. O$$ + $$O_3$$ \rightarrow 2O_2$$
Which species is a reaction intermediate?

Accepted Answer

$$O$$

Question 17

A reaction is found to be zero order with respect to reactant $$A. $$Which of the following is true?

Accepted Answer

The rate of the reaction is independent of $$[A].$$

Question 18

Which of the following is a real-world example of a catalyst in biological systems?

Accepted Answer

Sucrase catalyzing the breakdown of sucrose into glucose and fructose.

Question 19

If a reaction is second order with respect to $$A$$, which equation describes the relationship between $$[A]$$ and time?

Accepted Answer

$$1/[A]_t - 1/[A]_0 = kt$$

Chemical Kinetics: Reaction Rates, Mechanisms, and Catalysis

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