Q: Given the reaction $$2HI(g) \rightarrow H_2$(g) + I_2$(g)$$, which of the following is the correct expression for the rate in terms of the change in concentration of each species?

$$\text{Rate} = -\frac{1}{2} \frac{\Delta [HI]}{\Delta t} = \frac{\Delta [H_2$]}{\Delta t} = \frac{\Delta [I_2$]}{\Delta t}$$

Q: For the reaction $$aA + bB \rightarrow cC + dD$$, which of the following is the correct general rate expression?

$$\text{Rate} = -\frac{1}{a} \frac{\Delta [A]}{\Delta t} = -\frac{1}{b} \frac{\Delta [B]}{\Delta t} = \frac{1}{c} \frac{\Delta [C]}{\Delta t} = \frac{1}{d} \frac{\Delta [D]}{\Delta t}$$

Question 1

Which of the following best describes the rate of a chemical reaction as shown in the study materials?

Accepted Answer

The rate is the change in concentration of a reactant or product per unit time.

Question 2

Given the reaction $$2HI(g) \rightarrow H_2$(g) + I_2$(g)$$, which of the following is the correct expression for the rate in terms of the change in concentration of each species?

Accepted Answer

$$	ext{Rate} = -\frac{1}{2} \frac{\Delta [HI]}{\Delta t} = \frac{\Delta [H_2$]}{\Delta t} = \frac{\Delta [I_2$]}{\Delta t}$$

Question 3

A reaction has a rate constant $$k$$ that increases as temperature increases. Which equation best describes this relationship?

Accepted Answer

$$k = A e$$^{-\frac{E_a}$${RT}}$$

Question 4

For the reaction $$aA + bB \rightarrow cC + dD$$, which of the following is the correct general rate expression?

Accepted Answer

$$	ext{Rate} = -\frac{1}{a} \frac{\Delta [A]}{\Delta t} = -\frac{1}{b} \frac{\Delta [B]}{\Delta t} = \frac{1}{c} \frac{\Delta [C]}{\Delta t} = \frac{1}{d} \frac{\Delta [D]}{\Delta t}$$

Question 5

Which of the following statements about catalysts is TRUE based on the study materials?

Accepted Answer

A catalyst lowers the activation energy of a reaction but does not change the overall energy change ($$\Delta G) of $$the reaction.

Question 6

Given the Arrhenius equation $$\ln \left( \frac{k_2$}{k_1$} \right) = \frac{E_a}{R} \left( \frac{1}{T_1$} - \frac{1}{T_2$} \right)$$, what does $$E_a$$ represent?

Accepted Answer

The activation energy of the reaction

Question 7

A reaction is monitored and the plot of $$\ln [A]$$ versus time is a straight line. What is the order of the reaction with respect to A?

Accepted Answer

First order

Question 8

Which of the following best explains why increasing temperature generally increases the rate of a chemical reaction?

Accepted Answer

More molecules have sufficient energy to overcome the activation energy barrier.

Question 9

In a two-step reaction mechanism, which step determines the overall rate of the reaction?

Accepted Answer

The slowest (rate-determining) step

Question 10

For the reaction $$2NO_2Cl(g) \rightarrow 2NO_2(g) + Cl_2$(g)$$, the mechanism is proposed as follows:
Step 1: $$NO_2Cl \rightarrow NO_2$ + Cl ($$slow)
Step 2: $$NO_2Cl + Cl \rightarrow NO_2$ + Cl_2$ (fast)
What is the predicted rate law for this reaction?

Accepted Answer

$$	ext{Rate} = k[NO_2Cl]$$

Question 11

A reaction has a rate constant $$k = 0.0614\ 	ext{s}^{-1} at$$ $$T = 1000\ 	ext{K}. If $$the activation energy is $$E_a = 75\ 	ext{kJ/mol}$$, what will happen to the rate constant if the temperature is increased to $$1100\ 	ext{K}$$? (Assume $$A is $$constant.)

Accepted Answer

The rate constant will increase.

Question 12

Which of the following is NOT a characteristic of a catalyst?

Accepted Answer

A catalyst changes the position of equilibrium.

Question 13

If a reaction is first order in $$A$$ and second order in $$B$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 14

Which of the following best describes the effect of a catalyst on a reaction energy diagram?

Accepted Answer

It lowers the activation energy but does not change the energy of reactants or products.

Question 15

A reaction is monitored and the plot of $$1/[A]$$ versus time is a straight line. What is the order of the reaction with respect to A?

Accepted Answer

Second order

Question 16

Which of the following is the correct unit for the rate constant $$k$$ for a second-order reaction?

Accepted Answer

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

Question 17

In the context of reaction mechanisms, what is an intermediate?

Accepted Answer

A species that is formed in one step and consumed in a subsequent step of the mechanism.

Question 18

Which of the following best describes an effective collision in a chemical reaction?

Accepted Answer

A collision in which reactant molecules have sufficient energy and proper orientation to form products.

Question 19

If the rate law for a reaction is $$	ext{Rate} = k[A][B]^2$$, by what factor does the rate change if $$[B] is $$doubled while $$[A]$$ remains constant?

Accepted Answer

The rate increases by a factor of 4.

Chemical Kinetics: Reaction Rates, Mechanisms, and Catalysis

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