Question 1

Which of the following best explains why fireworks explode rapidly when ignited, as seen in the first image?

Accepted Answer

The reaction mixture is finely divided, increasing surface area and allowing for rapid collisions between reactant particles.

Question 2

Refer to the image of the rusty nail. Which factor most likely caused the nail on the right to rust faster than the others?

Accepted Answer

It was exposed to a higher concentration of oxygen and moisture, increasing the rate of the oxidation reaction.

Question 3

The energy profile shown in the third image represents an endothermic reaction. Which statement is correct about the activation energy ($$E_a) in $$this reaction?

Accepted Answer

The activation energy is the minimum energy that reactant molecules must absorb to reach the transition state.

Question 4

Which of the following best describes the effect of increasing temperature on the motion of gas molecules, as depicted in the fourth image?

Accepted Answer

The molecules move faster, increasing both the frequency and energy of collisions.

Question 5

Based on the fifth image, why does increasing the surface area of a solid reactant increase the rate of reaction?

Accepted Answer

It allows more reactant particles to be exposed and available for collisions with other reactants.

Question 6

Refer to the sixth image. What is the primary effect of an enzyme on a chemical reaction?

Accepted Answer

It lowers the activation energy, allowing more molecules to react.

Question 7

Which of the following is true about the catalyzed and uncatalyzed reactions shown in the seventh image?

Accepted Answer

The catalyzed reaction has a lower activation energy but the same overall energy change as the uncatalyzed reaction.

Question 8

Given the rate law $$	ext{Rate} = k[A][B]^2$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 9

A reaction has the rate law $$	ext{Rate} = k[A]^0. $$What will happen to the rate if the concentration of A is doubled?

Accepted Answer

The rate will remain unchanged.

Question 10

For a first-order reaction, which of the following graphs will yield a straight line?

Accepted Answer

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

Question 11

The half-life ($$t_{1/2}) $$for a first-order reaction is given by which equation?

Accepted Answer

$$t_{1/2} = \dfrac{0.693}{k}$$

Question 12

Which of the following statements about reaction mechanisms is correct?

Accepted Answer

The slowest step in the mechanism determines the rate law.

Question 13

A reaction is found to be second order overall. Which of the following rate laws is NOT possible for this reaction?

Accepted Answer

$$	ext{Rate} = k[A][B]^2$$

Question 14

If a reaction is first order in A and second order in B, what will happen to the rate if [A] is doubled and [B] is tripled?

Accepted Answer

The rate will increase by a factor of 12.

Question 15

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

It provides an alternative pathway with a lower activation energy.

Question 16

In the decomposition of hydrogen peroxide, $$2H_2O_2 \rightarrow 2H_2O + O_2$, why is $$MnO_2$$ often added?

Accepted Answer

To act as a catalyst and speed up the reaction.

Question 17

Which of the following is a correct statement about reaction intermediates?

Accepted Answer

They are produced in one step and consumed in another step of the mechanism.

Question 18

A reaction has the following mechanism:
Step 1 (slow): $$A + B \rightarrow C$$
Step 2 (fast): $$C + D \rightarrow E$$
What is the rate law for this reaction?

Accepted Answer

$$	ext{Rate} = k[A][B]$$

Question 19

Which of the following changes will NOT increase the rate of a chemical reaction?

Accepted Answer

Decreasing the temperature.

Chemical Kinetics: Rates, Mechanisms, and Factors Affecting Reaction Speed

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