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 $$2N_2O_5(g) \rightarrow 4NO_2(g) + O_2$(g)$$, if the rate of formation of $$NO_2 is$$ $$0.0072\ M/s$$, what is the rate of disappearance of $$N_2O_5$$?

Accepted Answer

$$0.0018\ M/s$$

Question 3

Which factor does NOT generally increase the rate of a chemical reaction?

Accepted Answer

Decreasing the temperature.

Question 4

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternate pathway with lower activation energy.

Question 5

Given the rate law $$rate = k[A]^2[B]$$, what are the units of the rate constant $$k$$?

Accepted Answer

$$M^{-2}$$\cdot $$s^{-1}$$

Question 6

If the initial concentration of reactant A is $$0.50\ M$$ and after $$30\ s it is$$ $$0.40\ M$$, what is the rate of disappearance of A?

Accepted Answer

$$-0.0033\ M/s$$

Question 7

Which statement about the overall rate of a chemical reaction is TRUE?

Accepted Answer

It is always positive, regardless of which reactant or product is used to calculate it.

Question 8

For a first-order reaction, which equation correctly relates the concentration of reactant A at time $$t to $$its initial concentration?

Accepted Answer

$$[A]_t = [A]_0 e$$^{-kt}$$

Question 9

Which of the following best explains why powdered coffee creamer can be explosive under certain conditions?

Accepted Answer

Increasing surface area allows for rapid reaction with oxygen, increasing the rate of combustion.

Question 10

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

Accepted Answer

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

Question 11

Which of the following is NOT a correct method for determining the order of a reactant in a rate law?

Accepted Answer

Using the stoichiometric coefficient from the balanced equation.

Question 12

The Arrhenius equation relates the rate constant $$k to $$temperature $$T$$ and activation energy $$E_a. $$Which is the correct form?

Accepted Answer

$$k = A e$$^{-E_a/(RT)}$$

Question 13

A reaction is found to be zero-order with respect to reactant A. What does this mean?

Accepted Answer

The rate does not depend on the concentration of A.

Question 14

If the activation energy for a reaction is increased, what is the expected effect on the rate constant $$k$$?

Accepted Answer

The rate constant $$k$$ decreases.

Question 15

For the reaction $$A + 2B \rightarrow C$$, the rate law is found to be $$rate = k[A][B]^2. If$$ $$[A] is $$doubled and $$[B] is $$tripled, by what factor does the rate increase?

Accepted Answer

18

Question 16

Which of the following is a correct statement about the effect of temperature on reaction rate?

Accepted Answer

Increasing temperature increases the rate by increasing the number of effective collisions.

Question 17

A student observes that a reaction proceeds much faster when the reactants are ground into a fine powder. This is primarily due to:

Accepted Answer

Increased surface area leading to more frequent collisions.

Question 18

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

Accepted Answer

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

Question 19

In a reaction mechanism, the slowest elementary step is called:

Accepted Answer

The rate-determining step.

Question 20

A reaction has a rate law $$rate = k[A][B]. If $$the initial rate is $$0.10\ M/s$$ when $$[A] = 0.20\ M$$ and $$[B] = 0.50\ M$$, what is the value of $$k$$?

Accepted Answer

$$1.0\ M$$^{-1}$$s^{-1}$

Chapter 15: Chemical Kinetics – Study Notes

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