Question 1

Which of the following best describes the difference between the reactions shown in the first and second images (flask with bright reaction vs. rusty nails)?

Accepted Answer

The first reaction is a fast, exothermic reaction, while the second is a slow, spontaneous process.

Question 2

Given the following rate law: $$	ext{rate} = k[Br_2$]^1[HCOOH]^0$$, what is the overall order of the reaction?

Accepted Answer

First order

Question 3

A reaction has the following rate law: $$	ext{rate} = k[A]^2[B]. If $$the concentration of A is doubled and B is halved, by what factor does the rate change?

Accepted Answer

The rate increases by a factor of 2

Question 4

Which of the following statements about the activation energy ($$E_a) is $$correct?

Accepted Answer

It is the minimum energy required for a reaction to occur.

Question 5

For a first-order reaction, which of the following plots yields a straight line?

Accepted Answer

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

Question 6

The decomposition of $$NO_2 is $$second order with respect to $$NO_2. If $$the initial concentration is $$3.00 	imes 10$$^{-3}$$ \ M$$ and the rate constant is $$0.54 \ M$$^{-1}$$s^{-1}$$, what is the half-life ($$t_{1/2}$) of the reaction?

Accepted Answer

$$t_{1/2} = \frac{1}{k[A]_0}$$

Question 7

Which of the following best explains why a catalyst increases the rate of a chemical reaction?

Accepted Answer

It lowers the activation energy ($$E_a) $$for the reaction.

Question 8

Consider the Arrhenius equation: $$\ln k = \left(-\frac{E_a}{R}\right)\left(\frac{1}{T}\right) + \ln A. $$What does the slope represent in a plot of $$\ln k vs$$. $$1/T$$?

Accepted Answer

The slope is $$-E_a/R$$

Question 9

Which of the following is true about the rate-determining step in a reaction mechanism?

Accepted Answer

It is the slowest step and determines the overall rate law.

Question 10

A reaction is found to be zeroth order in reactant A. Which of the following statements is correct?

Accepted Answer

The rate of reaction does not depend on the concentration of A.

Question 11

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

Accepted Answer

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

Question 12

Which of the following is a characteristic of a homogeneous catalyst?

Accepted Answer

It is in the same phase as the reactants.

Question 13

If the rate law for a reaction is $$	ext{rate} = k[A][B]^2$$, what are the units of the rate constant $$k$$?

Accepted Answer

$$M^{-2}$$ $$s^{-1}$$

Question 14

Which of the following is NOT a requirement for a proposed reaction mechanism to be valid?

Accepted Answer

Each elementary step must involve only one reactant molecule.

Question 15

A reaction has a rate law $$	ext{rate} = k[A]. If $$the initial concentration of A is 0.100 M and the rate constant is $$0.020 \ s$$^{-1}$$, what is the half-life (t$$_{1/2}$$) of the reaction?

Accepted Answer

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

Question 16

Which of the following best describes the effect of temperature on reaction rate according to collision theory?

Accepted Answer

Increasing temperature increases the frequency and energy of collisions, leading to a higher reaction rate.

Question 17

Which of the following is true about the molecularity of an elementary reaction?

Accepted Answer

It refers to the number of reactant molecules involved in a single collision.

Question 18

A catalyst is added to a reaction at equilibrium. What is the effect on the equilibrium position and the rate at which equilibrium is achieved?

Accepted Answer

The equilibrium position is unchanged, but equilibrium is reached faster.

Question 19

Which of the following is a correct statement about enzymes?

Accepted Answer

They are biological catalysts that are highly specific for their substrates.

Chemical Kinetics: Reaction Rates and Mechanisms

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