Q: For the reaction $$2NO_2(g) \rightarrow 4NO(g) + O_2$(g)$$, which expression correctly relates the rate of disappearance of $$NO_2 to $$the rate of appearance of $$NO$$?

$$\text{Rate} = -\frac{1}{2} \frac{d[NO_2$]}{dt} = \frac{1}{4} \frac{d[NO]}{dt}$$

Question 1

Which of the following statements best describes the difference between the average rate and the instantaneous rate of a chemical reaction?

Accepted Answer

The average rate is calculated over a finite time interval, while the instantaneous rate is the rate at a specific moment, given by the derivative $$\frac{d[A]}{dt}.$$

Question 2

For the reaction $$2NO_2(g) \rightarrow 4NO(g) + O_2$(g)$$, which expression correctly relates the rate of disappearance of $$NO_2 to $$the rate of appearance of $$NO$$?

Accepted Answer

$$	ext{Rate} = -\frac{1}{2} \frac{d[NO_2$]}{dt} = \frac{1}{4} \frac{d[NO]}{dt}$$

Question 3

Which factor does NOT directly affect the rate constant $$k in $$the Arrhenius equation?

Accepted Answer

Concentration of reactants

Question 4

A reaction is found to be first order in $$A$$ and second order in $$B. $$What is the correct rate law for this reaction?

Accepted Answer

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

Question 5

Which experimental method is most commonly used to determine the order of a reaction with respect to a particular reactant?

Accepted Answer

Isolation method (Initial Rates Method)

Question 6

For a first-order reaction, which of the following is the correct integrated rate law?

Accepted Answer

$$\ln[A] = -kt + \ln[A]_0$$

Question 7

A reaction has a rate law: $$	ext{Rate} = k[A]^0. $$What does this imply about the reaction?

Accepted Answer

The rate is independent of the concentration of $$A.$$

Question 8

Which of the following statements about catalysts is TRUE?

Accepted Answer

Catalysts lower the activation energy, increasing the rate constant $$k.$$

Question 9

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

Accepted Answer

Second order

Question 10

Which graphical method would you use to confirm a reaction is first order with respect to $$A$$?

Accepted Answer

Plot $$\ln[A] vs. $$time and look for a straight line

Question 11

For a second-order reaction, what is the expression for the half-life?

Accepted Answer

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

Question 12

Which of the following is NOT a valid assumption when using the initial rates method to determine reaction order?

Accepted Answer

Products are present in significant amounts at the start.

Question 13

The Arrhenius equation is given by $$k = Ae$$^{-E_a/(RT)}$$. What does E_a$ represent?

Accepted Answer

The activation energy required for the reaction to occur

Question 14

Which of the following mechanisms is consistent with a rate law $$	ext{Rate} = k[NO_2$]^2$$ for the reaction $$2NO_2 ightarrow 2NO + O_2$?

Accepted Answer

A single elementary step involving two $$NO_2$$ molecules colliding

Question 15

Which statement about reaction mechanisms is correct?

Accepted Answer

A proposed mechanism is supported if its rate law matches the experimental rate law.

Question 16

For a zero-order reaction, which of the following is true about the concentration of reactant $$A$$ over time?

Accepted Answer

$$[A]$$ decreases linearly with time

Question 17

Which of the following would most likely increase the rate of a reaction according to collision theory?

Accepted Answer

Increasing the concentration of reactants

Question 18

In a reaction mechanism, what is the rate-determining step?

Accepted Answer

The slowest elementary step, which controls the overall reaction rate

Question 19

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

Accepted Answer

It is in the same phase as the reactants.

Question 20

A student is studying the decomposition of $$H_2O_2$$ and finds that doubling the concentration of $$H_2O_2$$ doubles the rate. What is the order of the reaction with respect to $$H_2O_2$$?

Accepted Answer

First order

Chemical Kinetics: Rates, Mechanisms, and Catalysis

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