Q: Which of the following is the correct rate expression for the reaction $$2\mathrm{N}_2\mathrm{O}_5(s) \rightarrow 4\mathrm{NO}_2(g) + \mathrm{O}_2(g)$$?

$$\text{rate} = -\dfrac{1}{2}\dfrac{\Delta[\mathrm{N}_2\mathrm{O}_5]}{\Delta t} = \dfrac{1}{4}\dfrac{\Delta[\mathrm{NO}_2]}{\Delta t} = \dfrac{1}{1}\dfrac{\Delta[\mathrm{O}_2]}{\Delta t}$$

Question 1

Which of the following statements about the rate of a chemical reaction is TRUE?

Accepted Answer

The rate of reaction is always positive and has units of $$\mathrm{M\ s$$^{-1}$$}.$$

Question 2

For the reaction $$2\mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2\mathrm{H}_2\mathrm{O}(g)$$, if $$[\mathrm{O}_2] is $$decreasing at a rate of $$0.24\ \mathrm{M\ s$$^{-1}$$}$$, at what rate is $$[\mathrm{H}_2\mathrm{O}]$$ increasing?

Accepted Answer

$$0.48\ \mathrm{M\ s$$^{-1}$$}$$

Question 3

Which of the following is the correct rate expression for the reaction $$2\mathrm{N}_2\mathrm{O}_5(s) \rightarrow 4\mathrm{NO}_2(g) + \mathrm{O}_2(g)$$?

Accepted Answer

$$	ext{rate} = -\dfrac{1}{2}\dfrac{\Delta[\mathrm{N}_2\mathrm{O}_5]}{\Delta t} = \dfrac{1}{4}\dfrac{\Delta[\mathrm{NO}_2]}{\Delta t} = \dfrac{1}{1}\dfrac{\Delta[\mathrm{O}_2]}{\Delta t}$$

Question 4

Which statement about reaction order is correct?

Accepted Answer

Reaction order must be determined experimentally and is not related to stoichiometric coefficients.

Question 5

Given the rate law $$	ext{rate} = k[\mathrm{NO}]^2[\mathrm{H}_2]$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 6

A first-order reaction has a rate constant $$k = 6.7 	imes 10$$^{-4}$$\ \mathrm{s}^{-1}. $$What is the half-life of the reaction?

Accepted Answer

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

Question 7

For a second-order reaction, which plot will yield a straight line?

Accepted Answer

$$\dfrac{1}{[\mathrm{A}]} vs. $$time

Question 8

A zero-order reaction has an initial concentration $$[A]_0 = 0.689\ \mathrm{M}$$ and $$k = 6.70 	imes 10$$^{-3}$$\ \mathrm{M\ s$$^{-1}$$}. $$What is the concentration after $$84.0\ \mathrm{s}$$?

Accepted Answer

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

Question 9

Which factor does NOT affect the rate of a chemical reaction?

Accepted Answer

Color of the reactants

Question 10

According to collision theory, which condition is NOT required for a reaction to occur?

Accepted Answer

Reacting molecules must collide with a catalyst present.

Question 11

The Arrhenius equation relates the rate constant $$k to $$which variables?

Accepted Answer

Activation energy and temperature

Question 12

Which of the following is the correct integrated rate law for a first-order reaction?

Accepted Answer

$$\ln\left(\dfrac{[A]_t}{[A]_0}\right) = -kt$$

Question 13

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternative pathway with lower activation energy

Question 14

Which statement about the half-life of a first-order reaction is correct?

Accepted Answer

It is independent of the initial concentration of the reactant.

Question 15

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

Accepted Answer

The slowest elementary step

Question 16

Which of the following is an example of heterogeneous catalysis?

Accepted Answer

Catalytic converter in a car exhaust system

Question 17

For a second-order reaction, the half-life is given by:

Accepted Answer

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

Question 18

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

Accepted Answer

All intermediates must appear in the overall balanced equation.

Question 19

Which of the following is the correct integrated rate law for a zero-order reaction?

Accepted Answer

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

Question 20

Which of the following best describes an intermediate in a reaction mechanism?

Accepted Answer

A species that is formed in one elementary step and consumed in a later step.

Chemical Kinetics: Reaction Rates and Mechanisms (CHM 230 - Chapter 17 Study Notes)

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