mod 5 pt 2 chi

A(n) ____ is a protein that acts as a biological catalyst.

enzyme

Biological reactions are catalyzed by ______.

enzymes

For the reaction represented by the accompanying reaction energy diagram, the _____ step is _____ and is rate limiting.

first; slower

Correctly order the steps necessary to assess the validity of the mechanism shown, if the observed rate law is rate = k[A][B][C].

1. fast step 2. [X] 3. rate

A catalyst that exists in solution with the reaction mixture is called a ______ catalyst.

homogeneous

A ___ catalyst exists in solution with the reaction mixture, so it must be a gas, liquid, or soluble solid.

homogenous

A reaction _____ is a species that is formed and then used up during the course of a reaction.

intermediate

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.

lower; increasing

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

providing an alternative reaction mechanism that has a lower activation energy

The rate law for an overall reaction is equal to the rate law for the ___-___ step.

rate limiting

What is the predicted overall rate law from the proposed mechanism shown?

rate = k[(CH3)3C-Br]

For any mechanism, only _____ involved up to and including the_____step appear in the overall rate law.

reactants slow

What are the most common types of heterogeneous catalysts?

solids

A _____ is a substance that increases the rate of a reaction without being consumed. This type of substance is often used up and regenerated during the reaction.

Catalyst

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

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

A _____ catalyst that is in a different phase than the reactants is a(n) catalyst.

Heterogeneous

Which of the following species will not appear in the overall rate law for the proposed mechanism? 2NO(g) ⇌ N2O2(g) [fast] N2O2(g) + O2(g) → 2NO2(g) [slow]

NO2 N2O2

Which elementary step in the proposed mechanism is the rate-limiting step?

(2) X (g) + C (g) → Y (g); [slow]

Identify the reaction intermediate(s) in the reaction mechanism shown.

(CH3)3C-OH2+ (CH3)3C+

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

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

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

Reaction intermediates do not appear in the overall equation for the reaction. Reaction intermediates are formed and used up over the course of a reaction.

What is the molecularity of the elementary step A (g) + B (g) + C (g) → D (g)?

Termolecular

The reaction NO2 (g) + CO (g) → NO (g) + CO2(g) has ΔH°overall = -226 kJ/mol. A proposed reaction mechanism is shown. Choose the statement(s) that accurately describe the reaction energy diagram for the above reaction.

The Ea of the first step will be larger than the second or third step. The energy of the products will be lower than the energy of the reactants. There will be three peaks.

Consider the oxidation of chloride ions by hydrogen peroxide in acidic solution: 2Cl- + H2O2 + 2H+ → Cl2 + 2H2O The proposed mechanism is: (1) H+ + H2O2 ⇌ H2O+-OH [fast, reversible] (2) H2O+-OH + Cl- → HOCl + H2O [slow; rate determining] (3) HOCl + H+ + Cl- → Cl2 + H2O [fast] The observed rate law is: Rate = k[H2O2][H+][Cl-] Select the correct statements about the validity of the mechanism. Select all that apply,

The elementary steps add up to the overall balanced equation. The mechanism correlates with the overall rate law.

Which of the following criteria must be met for a reaction mechanism to be considered valid? Select all that apply.

The elementary steps must be physically reasonable. The elementary steps must add up to the overall balanced reaction. The mechanism must correlate with the experimentally determined rate law.

True or false: The rate law for an elementary step can be deduced from its reaction stoichiometry (i.e., from the balanced equation for the step).

True

Which of the following statements correctly describe the key aspects of drawing a reaction energy diagram? Select all that apply.

Intermediates will be higher in energy than any reactants or products. For an exothermic reaction, the energy of the products is less than the energy of the reactants.

The rate law for the reaction NO2 (g) + CO (g) → NO (g) + CO2 (g) is given by rate = k[NO2]2. Consider the mechanism depicted in the illustration. Which options correctly describe the validity of this mechanism? Select all that apply.

The mechanism does agree with the experimental rate law. The elementary steps add up to the overall balanced equation.

Which of the following statements correctly describe the reaction energy diagram in the illustration? Select all that apply.

The reaction mechanism consists of 2 elementary steps. The reaction is exothermic.

What is the reaction intermediate in this two-step mechanism? (1) X + O3 → XO + O2 (2) XO + O → X + O2

XO

Consider the mechanism shown. If the observed rate law is rate = k[NO]2[Br2] is the proposed mechanism valid? What is the rate law for the proposed mechanism? Select all that apply.

Yes, this mechanism is valid. rate = k2 k1k−1[NO]2[Br2] or rate = k[NO]2[Br2]