CH 16 Smart Book part 1

Express the rate of reaction in terms of the change in concentration of each of the reactants and products in the reaction A (g) + 2B (g) → C (g).

- Δ[A]Δt = - 12 Δ[B]Δt = Δ[C]

In order to determine reaction orders experimentally, a series of experiments are run in which the initial concentration of one reactant is ___ while the initial concentration of the other is kept ___ . The effect of the initial concentration on the initial rate is then evaluated in each case.

changed constant

Each reaction has its own characteristic reaction rate, which is determined by the nature of the reacting species. However, reaction rate can be influenced by increasing the frequency and energy of the ___ between molecules.

collisions

True or False: In rate law expressions, reaction orders may be negative or fractions.

t

Select the correct form for the half-life expression for a zero-order reaction.

t1/2 = [A]02k

A first-order reaction of A → B has a rate constant of 3.5 s-1. How long will it take for the concentration of A to decrease to 25% of its initial amount?

0.40 s

Cyclopropane undergoes isomerization in a first-order reaction with a rate constant of 0.1 s-1. If the initial concentration is 1.0 M, what is the concentration of the isomer propylene product after 10 seconds?

0.63 M

Why does the rate of a reaction generally decrease over time?

As reactant is used up, there are fewer reactant particles to collide and therefore fewer effective collisions.

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

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

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

Fractional numbers Zero Negative integers Positive integers

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.

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

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

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

The molecular scenes show three experiments at a given temperature involving reactants X (black) and Y (green), with their initial rates (in mol/L⋅s). If the rate law is rate = k[X]2, which options correctly identify the initial rate for Expt 2 and the expected appearance of the scene for Expt 3?

Initial rate for Expt 2 = 0.25 x 10-5 Expt 3 would depict 6 black spheres.

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

Spectrometric methods Change in electrical conductivity Change in pressure over time

Which of the following statements correctly describe the half-life of a reaction? Select all that apply.

The half-life of a reaction is related to its rate constant. The half-life of a first-order reaction is independent of the initial concentration. The half-life of a reaction is the time it takes for [A]0 to drop to half its original value.

Which of the following factors are affected by an increase in reactant concentration? Select all that apply.

The number of reactant collisions The rate of reaction The number of reactant particles in a given volume

Which of the following options correctly describe the reaction CH3CHO (g) → CH4 (g) + CO (g) where the rate = k[CH3CHO]3/2? Select all that apply.

The overall order is 32 . The reaction order is 32 with respect to CH3CHO.

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.)

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.

Select the correct form of the zero-order integrated rate law for one reactant.

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

If only reactants are initially added to a reaction flask, which species decrease in concentration during the course of the reaction N2 (g) + 3H2 (g) → 2NH3 (g)? Select all that apply.

[H2] [N2]

When determining reaction orders by experiment, the most common procedure is to ______.

change the concentration of one reactant while keeping the other concentrations constant

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

decrease; increase

The rate of a reaction _____ over time because as the reactant is used up, there are _____ reactant particles to collide.

decreases; fewer

True or false: Based on the balanced equation N2 (g) + 3H2 (g) → 2NH3 (g), the rate law is given by rate = k[N2][H2]3.

f

Select the correct form of the first-order integrated rate law for one reactant.

ln[A]0[A]t = kt

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

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

Reactant concentration decreases _____ quickly in a reaction with a higher rate than in a reaction with a lower rate.

more

Select the correct form of the second-order integrated rate law for one reactant.

1[A]t - 1[A]0 = kt

Write a balanced chemical equation for the reaction that has the following rate equation: Rate = - 12 Δ[N2O5]Δt = 14Δ[NO2]Δt = Δ[O2]Δt

2N2O5 (g) → 4NO2 (g) + O2 (g)

Determine the overall reaction order for the reaction 4A (g) + 3B (g) → 2C (g) from the experimental data provided.

3

Determine the rate constant for the reaction 4A (g) + 3B (g) → 2C (g) given the accompanying experimental data. The rate law for this reaction is given by rate = k[A]2[B].

5.00 × 103 L2/mol2⋅min

Which of the following statements best describes the effect of reactant concentration on reaction rate?

As reactant concentration increases, the number of reactant collisions increases, which in turn increases the reaction rate.

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

Increasing the surface area of the reactants Increasing the concentration 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. If there is more than one reactant present the reaction orders will usually be determined individually. The value of k can be calculated from a single experiment once the reaction orders are known.

Chemical kinetics studies the ___ of chemical reactions, i.e., how fast reactants are converted into products.

rate