Question 1

Which of the following best describes the instantaneous rate of a chemical reaction as shown in the first image?

Accepted Answer

It is the rate measured at a specific moment, represented by the slope of the tangent to the curve at that point.

Question 2

In the reaction $$\mathrm{H_2$(g) + I_2$(g) \rightarrow 2HI(g)}$$, as shown in the third image, why does the concentration of HI increase twice as fast as the concentration of H$$_2$$ decreases?

Accepted Answer

Because the stoichiometry of the reaction produces 2 moles of HI for every 1 mole of H$$_2$$ consumed.

Question 3

Which experimental technique, as depicted in the fourth image, is commonly used to monitor the concentration of a reactant over time in a chemical kinetics experiment?

Accepted Answer

Spectrophotometry

Question 4

According to Beer’s Law, which is used in spectrophotometry, how is absorbance ($$A) $$related to concentration ($$c$$)?

Accepted Answer

$$A = \epsilon b c$$

Question 5

For a first-order reaction, which of the following plots yields a straight line?

Accepted Answer

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

Question 6

Given the integrated rate law for a first-order reaction $$A \rightarrow$$ products: $$\ln \frac{[A]_t}{[A]_0} = -kt$$, what is the half-life ($$t_{1/2}) $$expression for this reaction?

Accepted Answer

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

Question 7

A reaction is found to have a rate law: $$	ext{Rate} = k[A]^2. If $$the initial concentration of $$A is $$doubled, how does the rate change?

Accepted Answer

The rate quadruples.

Question 8

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

The color of the reactants

Question 9

For the reaction $$2A \rightarrow B$$, the rate of disappearance of $$A is$$ $$0.10\ \mathrm{M/s}. $$What is the rate of appearance of $$B$$?

Accepted Answer

$$0.05\ \mathrm{M/s}$$

Question 10

Which statement about the half-life of a first-order reaction is correct, as illustrated in the fifth image?

Accepted Answer

The half-life is constant and independent of concentration.

Question 11

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

Accepted Answer

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

Question 12

For a second-order reaction with respect to $$A$$, which of the following is the correct integrated rate law?

Accepted Answer

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

Question 13

If a reaction is zero order, what will a plot of $$[A]$$ versus time look like?

Accepted Answer

A straight line with a negative slope

Question 14

Which of the following best explains why the rate constant $$k$$ has different units depending on the order of the reaction?

Accepted Answer

Because the units of concentration and time must balance the rate law equation for each reaction order.

Question 15

A student observes that a plot of $$\ln [A]$$ versus time is a straight line for a reaction. What can be concluded about the reaction?

Accepted Answer

The reaction is first order with respect to $$A.$$

Question 16

For a reaction $$A \rightarrow$$ products, the initial concentration of $$A is$$ $$0.50\ \mathrm{M}$$ and after one half-life, the concentration is $$0.25\ \mathrm{M}. If $$the reaction is first order, what will the concentration be after three half-lives?

Accepted Answer

$$0.0625\ \mathrm{M}$$

Chemical Kinetics: Rates, Rate Laws, and Integrated Rate Equations

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