Chapter 16

Which elementary step in the proposed mechanism is the rate-limiting step? Multiple choice question.

(2) X (g) + C (g) → Y (g); [slow]

Which of the following statements correctly describe a reaction mechanism? Select all that apply.

A reaction mechanism is a hypothesis. A reaction mechanism describes a series of single reaction steps that sum to the overall chemical equation.

Which of the following statements correctly describe catalysts? Select all that apply. Multiple select question.

Catalysts lower the activation energy of the rate-determining step in the reaction. Catalysts provide a different mechanism for the reaction.

Which of the following statements correctly describe chemical kinetics? Select all that apply.

Chemical kinetics describes chemical reactions using collision theory. Chemical kinetics measures how fast reactants are converted into products. Chemical kinetics is the study of reaction rates.

In general, a catalyst speeds up a given reaction by providing an alternative mechanism that has a ______ activation energy, thus ______ the rate constant and the overall rate. Multiple choice question.

Lower;increasing

Select the parameters that are required for proposing a valid reaction mechanism. Select all that apply.

Physically reasonable elementary steps Correlation of rate law with experimental rate law Elementary steps sum to overall balanced equation

Which of the following are possible forms of a reaction order? Select all that apply. Multiple select question.

Positive integers Zero Fractional numbers Negative integers

Select common laboratory methods for determining the rate of a reaction.

Spectrometric methods Change in pressure over time Change in electrical conductivity

Which of the following statements correctly describes the activation energy of a reaction?

The energy threshold that the colliding particles must exceed in order to react

Which of the following statements correctly describe a rate law for a reaction? Select all that apply. (Assume that the reaction is not reversible to any appreciable extent.) Multiple select question.

The rate law relates the rate of reaction to the concentrations of the reactants. The rate law includes the rate constant for the reaction.

Which of the following statements correctly describe an integrated rate law? Select all that apply.

The reactant concentration at any time in the reaction can be determined from the integrated rate law. The value of the reaction constant, k, can be determined using an integrated rate law. An integrated rate law includes time as a variable.

Which of the following options correctly interpret the rate law rate = k[HNO2]4[NO]2[HNO2]4[NO]2? Select all that apply. Multiple select question.

The reaction order is -2 with respect to NO. If [NO] doubles the rate decreases by a factor of 4.

Which of the following statements correctly describe the transition state of a reaction? Select all that apply. Multiple select question.

The transition state species is highly unstable. The transition state only exists at the instant of highest potential energy in the reaction.

Which question(s) can be answered from an integrated rate law that cannot be answered by other forms of the rate law? Select all that apply.

What is [A] after y minutes of the reaction? How long will it take to use up x moles per liter of A?

An increase in temperature causes a _____ collision frequency and energy and therefore _____ the rate dramatically. Multiple choice question.

greater; increases

Select the correct form of the first-order integrated rate law for one reactant. Select all that apply. Multiple select question.

ln[A]0[A]t[A]0[A]t = kt ln[A]t - ln[A]0 = -kt

In general, a catalyst increases the rate of a reaction by _______. Multiple choice question.

providing an alternative reaction mechanism that has a lower activation energy

In the Arrhenius equation, k = Ae-Ea/RT. if T increases, the value of the negative exponent becomes _____, which means k becomes _____ and the rate _____.

smaller; larger; increases

What is an elementary step? Multiple choice question.

Each step that makes up a reaction mechanism

Which of the following changes would cause an increase in the reaction rate? Select all that apply. Multiple select question.

Increasing the concentration of the reactants Increasing the surface area of the reactants

Which of the following statements correctly describe how a rate law is determined? Select all that apply.

The rate law is determined by measuring the initial reaction rate for different reactant concentrations. The value of k can be calculated from a single experiment once the reaction orders are known. If there is more than one reactant present the reaction orders will usually be determined individually.

Which of the following options correctly interpret the rate law rate = k[HNO2]4[NO]2[HNO2]4[NO]2? Select all that apply.

The reaction order is -2 with respect to NO. If [NO] doubles the rate decreases by a factor of 4.

During the course of a reaction, reactant concentrations _____ and product concentrations _____.

Decrease;increase

Transition state theory focuses on which of the following?

The high-energy species that exists at the moment of an effective collision