Q: For a first-order reaction, which of the following plots will yield a straight line?

$$\ln([\text{Reactant}]) vs. $$time

Question 1

For a first-order reaction, which of the following plots will yield a straight line?

Accepted Answer

$$\ln([	ext{Reactant}]) vs. $$time

Question 2

A reaction has a rate law $$	ext{rate} = k[	ext{A}]^2[	ext{B}]. If $$the concentration of A is doubled and B is halved, by what factor does the rate change?

Accepted Answer

The rate is doubled.

Question 3

The decomposition of $$\mathrm{N_2O} at 1000 K $$has a half-life of 0.915 s. What is the rate constant $$k$$ for this first-order reaction?

Accepted Answer

$$k = 0.765\ \mathrm{s}^{-1}$$

Question 4

Which step is the rate-determining step in the following mechanism for $$2\ \mathrm{NO}(g) + \mathrm{O}_2(g) \rightarrow 2\ \mathrm{NO}_2(g)$$?

Step 1: $$2\ \mathrm{NO} \xrightleftharpoons[k_{-1}]{k_1$} \mathrm{N_2O_2} ($$fast)
Step 2: $$\mathrm{N_2O_2} + \mathrm{O_2$} \xrightarrow{k_2$} 2\ \mathrm{NO}_2 ($$slow)

Accepted Answer

Step 2

Question 5

For the reaction $$\mathrm{H_2$}(g) + \mathrm{I_2$}(g) \rightleftharpoons 2\ \mathrm{HI}(g)$$, if the initial concentrations of $$\mathrm{H_2$}$$ and $$\mathrm{I_2$}$$ are both 2.0 M and $$K_c = 6.9$$, what is the equilibrium concentration of $$\mathrm{HI}$$?

Accepted Answer

2.6 M

Question 6

According to the Law of Mass Action, what is the equilibrium constant expression for the reaction $$aA + bB \rightleftharpoons cC + dD$$?

Accepted Answer

$$K = \dfrac{[C]^c[D]^d}{[A]^a[B]^b}$$

Question 7

If the equilibrium constant $$K$$ for a reaction is $$2.0$$ and the equation is reversed, what is the new equilibrium constant?

Accepted Answer

$$K = 0.5$$

Question 8

For the reaction $$\mathrm{N_2O_4}(g) \rightleftharpoons 2\ \mathrm{NO_2$}(g)$$, a vessel is charged with $$0.0400$$ mol of $$\mathrm{N_2O_4} in a$$ $$1.00 L $$container. At equilibrium, $$0.00855$$ mol of $$\mathrm{N_2O_4}$$ remains. What is the value of $$K_c$$?

Accepted Answer

$$K_c = 0.0690$$

Question 9

Which of the following changes will shift the equilibrium to the right for the endothermic reaction $$\mathrm{CO_2$}(g) + 2\ \mathrm{H_2O}(l) \rightleftharpoons \mathrm{CH_4$}(g) + 2\ \mathrm{O_2$}(g)$$, $$\Delta H^\circ = +890\ \mathrm{kJ}$$?

Accepted Answer

Increase the temperature

Question 10

If the coefficients of a balanced chemical equation are multiplied by 2, how does the equilibrium constant $$K$$ change?

Accepted Answer

$$K is $$squared

Question 11

Which of the following statements about a dynamic equilibrium is correct?

Accepted Answer

The forward and reverse reaction rates are equal.

Question 12

For the reaction $$\mathrm{$$PCl_3$$}(g) + \mathrm{Cl_2$}(g) \rightleftharpoons \mathrm{$$PCl_5$$}(g)$$, if $$K_1 is $$the equilibrium constant for $$2\ \mathrm{$$PCl_3$$}(g) + 2\ \mathrm{Cl_2$}(g) \rightleftharpoons 2\ \mathrm{$$PCl_5$$}(g)$$ and $$K_2 is $$for $$\mathrm{$$PCl_5$$}(g) \rightleftharpoons \mathrm{$$PCl_3$$}(g) + \mathrm{Cl_2$}(g)$$, what is the equilibrium constant $$K$$ for the original reaction in terms of $$K_1$$ and $$K_2$$?

Accepted Answer

$$K = \sqrt{K_1$}$$

Question 13

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Lowering the activation energy

Question 14

Which of the following is true about the effect of adding an inert gas at constant volume to a reaction at equilibrium?

Accepted Answer

It has no effect on the position of equilibrium.

Question 15

For a zero-order reaction, what is the relationship between the concentration of reactant and time?

Accepted Answer

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

Question 16

In the Arrhenius equation $$\ln(k) = -\dfrac{E_a}{R} \left(\dfrac{1}{T}\right) + \ln(A)$$, what does the slope of a plot of $$\ln(k) vs$$. $$1/T$$ represent?

Accepted Answer

$$-E_a/R$$

Question 17

Which of the following is a requirement for a proposed reaction mechanism to be valid?

Accepted Answer

Both A and B

Question 18

For the reaction $$\mathrm{N_2O_4}(g) \rightleftharpoons 2\ \mathrm{NO_2$}(g)$$, if $$K_c is $$very small, which approximation can be used to simplify equilibrium calculations?

Accepted Answer

The change in concentration of reactants is negligible compared to the initial concentration.

Question 19

Which of the following best describes a reaction intermediate?

Accepted Answer

A species that is formed and consumed during the reaction mechanism.

Chem 132 Exam 2 Review: Chemical Kinetics and Equilibrium

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