Chapter 14 Test

Question 1

Using the following data for the reaction 2NO(g) + Br2(g) → 2NOBr(g), what are the values of m, n, and k in the rate law rate = k[ NO]m [Br2 ]n?

Answer 1

m = 2, n = 1, k = 9.8 M −2 • s−1

Question 2

Hydrogen gas reacts with iodine chloride to form iodine and hydrogen chloride as given by the balanced equation below:

H2(g) + 2ICl(g) → I2(g) + 2HCl(g)

The rate of the reaction can be measured in terms of the rate of decrease of [H2 ]. Using the graph below, calculate the average reaction rate for the time period 0.00 − 2.00 seconds.

Answer 2

0.237 M / s

Question 3

The following reaction is second order in [A] and second order overall.

2A → B + C

The instantaneous rate of reaction is 1.8 × 10−3 M / s when [A] is equal to 0.63 M. What is the rate constant, k, of this reaction?

Answer 3

4.5 × 10^−3 M −1s−1

Question 4

Bromate ions (BrO3− ) react with bromide and hydrogen ions according to the following equation.

BrO3− (aq) + 5Br− (aq) + 6H + (aq) → 3Br2(aq) + 3H2O(l)

Based on this reaction, which of the following relationships is true?

Answer 4

d [Br2 ] / dt = (−3/5) (d [Br− ] / dt)

Question 5

For the hypothetical reaction:

2A + xB -> yC + zD

Use the following rates to calculate x, y, and z
[A]/t = -0.062 M/s
[B]/t = -0.186 M/s
[C]/t = 0.093 M/s
[D]/t = 0.031 M/s

Answer 5

x = 6 y = 3 z = 2

Question 6

Iodide ions react with hypochlorite ions according to the following equation:

I − (aq) + OCl − (aq) → IO− (aq) + Cl − (aq)

A scientist gathers the following initial rate data for the reaction:

If the reaction is first order in [ I − ] and first order in [OCl − ], what is the missing value in the table?

Answer 6

3.2 × 10^−2 M / s

Question 7

Ammonium ions react with nitrite ions according to the following equation:

A scientist gathers the following initial rate data for the reaction.

What is the rate constant, k, for this reaction?

Answer 7

2.7 × 10^−4 M −1s−1

Question 8

Suppose you are studying the following reaction.

X → Y + Z

You gather the following initial rate data.

What is the half-life of the reaction?

Answer 8

1.3 s

Question 9

Cyclobutane (C4H8 ) forms ethylene (C2H4 ) according to the following equation.

C4H8 → 2C2H4

The half-life of this first-order reaction is 22.7 s. If the initial concentration of C4H8 is 1.42 M, what will be the rate of reaction at t = 60 s?

Answer 9

7.0 × 10^−3 M / s

Question 10

Phosphorus-32 is a radioactive isotope that decays according to the following reaction.

32P →32S + e−

The graph above shows ln [32P] versus time. What is the rate law of the decay of 32P?

Answer 10

rate = (4.9 × 10^−2 days−1 ) • [32P]

Question 11

Substance P undergoes the following reaction.

2P → Q + R

The graph above shows a plot of 1 / [P] versus time. What is the rate law of the reaction?

Answer 11

rate = (4.0 × 10^−2 M −1hr−1 ) • [P]2.

Question 12

In the Arrhenius equation the “A” is

Answer 12

the frequency factor

Question 13

For many reactions involving enzymes (E) reacting with substrates (S) to form products (P), steady state approximations can be applied to derive the rate law:

Which of the following shows the rate law when the concentration of substrate is very large in relation to the k values?

Answer 13

rate = kobs[E]0

Question 14

______ is an enzyme in blood which catalyzes the same reaction as iodide ion and manganese(IV) oxide.

Answer 14

catalase

Question 15

Why is the reaction 2NO2(g) + F2(g) → 2FNO2(g) extremely unlikely to proceed as a single elementary step?

Answer 15

Termolecular reactions are exceedingly unlikely

Question 16

Which of the following is the best description of a reaction mechanism?

Answer 16

A series of elementary steps that explain the overall reaction.

Question 17

NOBr2 is an intermediate, which is formed during the slow step of a reaction mechanism. Why is NOBr2 not used in the rate law?

Answer 17

The concentration of intermediates can not be measured

Question 18

What is referred to as dynamic equilibrium?

Answer 18

The rate of the forward reaction equals the rate of the reverse reaction.

Question 19

A catalyst has which of the following properties?

Answer 19

A catalyst increases the rate of a reaction.

Question 20

Which of the following is not an enzyme?

Answer 20

Lactose

Question 21

Find the initial concentration of a sucrose solution that has a current concentration of 3.45 g / L after 2 hours and 30 minutes at 25°C. For this reaction at 25°C, k = 4.10 × 10−2 hr−1.

Answer 21

3.82 g/L

Question 22

Gasoline is a mixture of hydrocarbons of various chain lengths, ranging from 5-carbon chains to 10-carbon chains. One of the hydrocarbons we often hear about is the 8-carbon chain, octane. Octane combusts with oxygen as given by the balanced equation:

2C8H18(g) + 25O2(g) → 16CO2(g) + 18H2O(g)

Recall that you cannot infer the reaction pathway from the balanced equation. It must be derived experimentally. Yet upon reading this balanced equation, it appears unlikely that the combustion of octane occurs in a single step. Why?

Answer 22

It would require the simultaneous collision of 27 molecules.

Question 23

The fundamental notion of collision theory is that in order for atoms, ions, or molecules to react what must be true?

Answer 23

They must first collide.

Question 24

How does an increase in temperature affect a chemical reaction?

Answer 24

The reaction speeds up.

Question 25

The rate law for the formation of NO2 from N2O5 is in what order for M when the concentration of M is very large?

Answer 25

Zero