Question 1

Which of the following best describes the general format of a rate law for the reaction $A + B \rightarrow C + D$?

Accepted Answer

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

Question 2

Why can't reaction orders for overall reactions be determined from stoichiometric coefficients?

Accepted Answer

Because rate laws are tied to the mechanism, not just the overall equation.

Question 3

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

Accepted Answer

3

Question 4

A reaction has the rate law $	ext{Rate} = k[A][B]^2$. If the concentration of $B$ is doubled while $A$ is kept constant, by what factor does the rate increase?

Accepted Answer

4

Question 5

Which of the following statements is TRUE regarding the proportionality constant $k$ in a rate law?

Accepted Answer

$k$ ensures proper unit cancellation in the rate law.

Question 6

Experimental data for a reaction shows that doubling $[A]$ while keeping $[B]$ constant doubles the rate, and doubling $[B]$ while keeping $[A]$ constant quadruples the rate. What is the rate law?

Accepted Answer

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

Question 7

Which experimental method is commonly used to determine reaction orders?

Accepted Answer

Method of Initial Rates

Question 8

For the reaction $2NO(g) + 2H_2(g) ightarrow N_2(g) + 2H_2O(g)$, the following data were collected:

Experiment 1: $[NO] = 0.10$ M, $[H_2] = 0.10$ M, Rate $= 1.23 	imes 10^{-3}$ M/s
Experiment 2: $[NO] = 0.20$ M, $[H_2] = 0.10$ M, Rate $= 4.92 	imes 10^{-3}$ M/s

What is the order with respect to $NO$?

Accepted Answer

2

Question 9

If the rate law for a reaction is $	ext{Rate} = k[A]^0[B]^1$, what does this imply about the effect of $[A]$ on the reaction rate?

Accepted Answer

The rate is independent of $[A]$.

Question 10

A student claims that the rate law for $A + B ightarrow C$ is $	ext{Rate} = k[A]^2[B]$ because the stoichiometric coefficient of $A$ is 2. What is wrong with this reasoning?

Accepted Answer

Reaction orders must be determined experimentally, not from stoichiometry.

Question 11

In a real-world scenario, the decomposition of hydrogen peroxide is catalyzed by iodide ion. If the rate law is $	ext{Rate} = k[H_2O_2][I^-]$, what happens to the rate if both $[H_2O_2]$ and $[I^-]$ are doubled?

Accepted Answer

The rate increases by a factor of 4.

Question 12

Which of the following is NOT a correct statement about rate laws?

Accepted Answer

Rate laws can be predicted from the overall balanced equation.

Question 13

A reaction has the rate law $	ext{Rate} = k[A]^1[B]^0$. If $[A]$ is tripled and $[B]$ is halved, what happens to the rate?

Accepted Answer

It triples.

Question 14

Why is it important to experimentally determine the reaction order for each reactant?

Accepted Answer

Because the reaction order reveals the mechanism of the reaction.

Question 15

If a reaction is zero order with respect to $B$, what will happen to the rate if $[B]$ is increased from 0.1 M to 0.5 M?

Accepted Answer

The rate will remain unchanged.

Question 16

A chemist finds that the rate law for a reaction is $	ext{Rate} = k[A]^2$. If the initial rate is $0.10$ M/s when $[A] = 0.50$ M, what will the rate be when $[A] = 1.00$ M?

Accepted Answer

0.40 M/s

Question 17

Which of the following best explains why rate laws are not written using product concentrations?

Accepted Answer

Products do not affect the rate of the forward reaction.

Question 18

A reaction has the rate law $	ext{Rate} = k[A]^1[B]^2$. If $[A]$ is doubled and $[B]$ is tripled, by what factor does the rate increase?

Accepted Answer

18

Rate Laws and Determining Reaction Orders in Chemical Kinetics

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