Q: Given the reaction $$2\text{N}_2\text{O}_5(g) \rightarrow 4\text{NO}_2(g) + \text{O}_2(g)$$, if the rate of decomposition of $$\text{N}_2\text{O}_5 is$$ $$2.48 \times 10$$^{-4}$$\ \mathrm{M/min}$$, what is the rate of formation of $$\text{NO}_2$$?

$$4.96 \times 10$$^{-4}$$\ \mathrm{M/min}$$

Q: The rate law for a reaction is $$\text{rate} = k[\text{NO}_2]^2. $$Which of the following mechanisms is consistent with this rate law?

A single-step bimolecular reaction: $$2\text{NO}_2 \rightarrow \text{products}$$

Question 1

Which of the following best describes the rate of a chemical reaction?

Accepted Answer

The change in concentration of a reactant or product per unit time.

Question 2

For the reaction $$2	ext{H}_2(g) + 2	ext{NO}(g) ightarrow 2	ext{H}_2	ext{O}(g) + 	ext{N}_2(g)$$, the rate law is found to be $$	ext{rate} = k[	ext{H}_2][	ext{NO}]^2. $$What is the overall order of the reaction?

Accepted Answer

Third order

Question 3

A reaction has the rate law $$	ext{rate} = k[	ext{A}]^2[	ext{B}]. $$What are the units of the rate constant $$k$$?

Accepted Answer

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

Question 4

Given the reaction $$2	ext{N}_2	ext{O}_5(g) ightarrow 4	ext{NO}_2(g) + 	ext{O}_2(g)$$, if the rate of decomposition of $$	ext{N}_2	ext{O}_5 is$$ $$2.48 	imes 10$$^{-4}$$\ \mathrm{M/min}$$, what is the rate of formation of $$	ext{NO}_2$$?

Accepted Answer

$$4.96 	imes 10$$^{-4}$$\ \mathrm{M/min}$$

Question 5

Which plot will yield a straight line for a first-order reaction?

Accepted Answer

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

Question 6

The half-life for a first-order reaction is given by:

Accepted Answer

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

Question 7

If the rate law for a reaction is $$	ext{rate} = k[	ext{X}]^2[	ext{Y}]^3$$, by what factor does the rate increase if $$[	ext{X}] is $$tripled and $$[	ext{Y}] is $$doubled?

Accepted Answer

The rate increases by a factor of 72.

Question 8

Which of the following statements about the Arrhenius equation is correct?

Accepted Answer

The rate constant $$k$$ increases as temperature increases.

Question 9

For a second-order reaction with respect to $$A$$, what is the integrated rate law?

Accepted Answer

$$\frac{1}{[A]_t} = \frac{1}{[A]_0} + kt$$

Question 10

A reaction is found to be zero order in $$A. If $$the initial concentration of $$A is$$ $$0.10\ \mathrm{M}$$ and the rate constant $$k = 0.020\ \mathrm{M/s}$$, how long will it take for $$A to $$decrease to $$0.04\ \mathrm{M}$$?

Accepted Answer

$$3.0\ \mathrm{s}$$

Question 11

Which of the following is NOT a requirement for a successful collision according to the collision model?

Accepted Answer

Reactants must be in the gas phase.

Question 12

The rate law for a reaction is $$	ext{rate} = k[	ext{NO}_2]^2. $$Which of the following mechanisms is consistent with this rate law?

Accepted Answer

A single-step bimolecular reaction: $$2	ext{NO}_2 ightarrow 	ext{products}$$

Question 13

For the reaction $$A \rightarrow B + C$$ which is second order in $$A$$, if $$[A]_0 = 0.100\ \mathrm{M}$$ and the reaction is $$20\%$$ complete in $$47.7$$ minutes, what is the half-life?

Accepted Answer

$$1.91 	imes 10^2$ min

Question 14

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

Accepted Answer

The step with the highest activation energy.

Question 15

A reaction has a rate law $$	ext{rate} = k[	ext{A}]^0. $$Which of the following statements is true?

Accepted Answer

The rate is constant and independent of $$[A].$$

Question 16

The Arrhenius equation is $$k = Ae$$^{-E_a/RT}$$. If E_a$ is in $$\mathrm{J/mol}$$, what are the units of R$?

Accepted Answer

$$\mathrm{J}\,\mathrm{mol}^{-1}\,\mathrm{K}^{-1}$$

Question 17

Which of the following is a correct expression for the rate of disappearance of $$	ext{H}_2 in $$the reaction $$	ext{H}_2(g) + I_2$(g) ightarrow 2	ext{HI}(g)$$?

Accepted Answer

$$	ext{rate} = -\frac{\Delta[	ext{H}_2]}{\Delta t}$$

Question 18

Which of the following rate laws is consistent with the following mechanism?
Step 1: $$	ext{H}_2	ext{O}_2 + 	ext{H}^+ ightleftharpoons 	ext{H}_2	ext{O}^+ + 	ext{OH}^- ($$fast, equilibrium)
Step 2: $$	ext{H}_2	ext{O}^+ + 	ext{OH}^- + 	ext{Br}^- ightarrow 	ext{HOBr} + 	ext{H}_2	ext{O} ($$slow)
Step 3: $$	ext{HOBr} + 	ext{H}^+ + 	ext{Br}^- ightarrow 	ext{Br}_2 + 	ext{H}_2	ext{O} ($$fast)

Accepted Answer

$$	ext{rate} = k[	ext{H}_2	ext{O}_2][	ext{H}^+][	ext{Br}^-]$$

Chemical Kinetics and Rate Laws: Mini-Textbook Study Guide

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