Q: For the reaction $$\mathrm{SO_3$(g)} \rightleftharpoons \frac{1}{2}\mathrm{O_2$(g)} + \mathrm{SO_2$(g)}$$, $$K_c = 7.7 \times 10$$^{-4}$$. What is K_c$ for 2$$\mathrm{$$SO_2(g$$)} + \mathrm{$$O_2(g$$)} \rightleftharpoons 2\mathrm{$$SO_3(g$$)}$$?

$$K_c = (7.7 \times 10$$^{-4}$$)^{-2}$

Question 1

For the reaction $$2\ \mathrm{C_2H_6(g)} + 7\ \mathrm{O_2$(g)} \rightarrow 4\ \mathrm{CO_2$(g)} + 6\ \mathrm{H_2O(g)}$$, if the rate of oxygen consumption is $$9.34\ \mathrm{M/s}$$, what is the rate of formation of $$\mathrm{CO_2$}$$?

Accepted Answer

$$5.34\ \mathrm{M/s}$$

Question 2

Given the experimentally observed rate law $$	ext{Rate} = k[\mathrm{Ce$$^{4+}$$}]^2[\mathrm{Mn$$^{2+}$$}]$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 3

The decomposition of $$\mathrm{N_2O} is $$first order with a rate constant $$k = 3.40\ \mathrm{s$$^{-1}$$}. $$What is the half-life if $$[\mathrm{N_2O}]_0 = 0.782\ \mathrm{M}$$?

Accepted Answer

$$t_{1/2} = \frac{0.693}{3.40}$$

Question 4

A second-order reaction has a rate constant $$k = 1.80 	imes 10$$^{-3}$$\ \mathrm{M$$^{-1}$$s^{-1}$$}$$ and initial $$[\mathrm{HI}]_0 = 4.78\ \mathrm{M}$$. How much HI remains after 27.3$$\ \mathrm{s}$?

Accepted Answer

$$[\mathrm{HI}] = \frac{1}{k t + \frac{1}{[\mathrm{HI}]_0}}$$

Question 5

The reaction $$\mathrm{C_2H_5Br} + \mathrm{OH^-} ightarrow \mathrm{C_2H_5OH} + \mathrm{Br^-}$$ has $$E_a = 89.5\ \mathrm{kJ/mol}$$ and $$k_{20^\circ C} = 4.76 	imes 10$$^{-5}$$\ \mathrm{M$$^{-1}$$s^{-1}$$}$$. What equation would you use to find k$ at 80$$^\circ C$?

Accepted Answer

$$\ln \frac{k_2$}{k_1$} = \frac{E_a}{R} \left( \frac{1}{T_1$} - \frac{1}{T_2$} \right)$$

Question 6

For the bromination of acetone, the initial rate does not change when $$[\mathrm{Br_2$}] is $$doubled, but increases when $$[\mathrm{CH_3COCH_3}] is $$increased. What is the order with respect to $$\mathrm{Br_2$}$$?

Accepted Answer

Zero order

Question 7

Which integrated rate law corresponds to a second-order reaction?

Accepted Answer

$$\frac{1}{[A]_t} = kt + \frac{1}{[A]_0}$$

Question 8

Given the following graphs for the decomposition of t-butyl chloride, which plot indicates a first-order reaction?

Accepted Answer

Plot of $$\ln [\mathrm{t-BuCl}] vs. $$time

Question 9

Write the $$K_p$$ expression for the reaction: $$\mathrm{P_4O_{10}(s)} \rightleftharpoons \mathrm{P_4$(s)} + 5\ \mathrm{O_2$(g)}.$$

Accepted Answer

$$K_p = P_{\mathrm{O_2$}}^5$$

Question 10

For the reaction $$\mathrm{N_2$(g)} + 3\ \mathrm{H_2$(g)} \rightleftharpoons 2\ \mathrm{NH_3$(g)}$$, what is the correct $$K_c$$ expression?

Accepted Answer

$$K_c = \frac{[\mathrm{NH_3$}]^2}{[\mathrm{N_2$}][\mathrm{H_2$}]^3}$$

Question 11

Given $$K_p = 5.4 	imes 10^5$ for ammonia formation at 298$$\ \mathrm{K}$$, which equation relates K_p$ and K_c$?

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$

Question 12

For the mechanism:
Step 1: $$\mathrm{Ce$$^{4+}$$} + \mathrm{Mn$$^{2+}$$} \rightarrow \mathrm{Ce$$^{3+}$$} + \mathrm{Mn$$^{3+}$$}$$
Step 2: $$\mathrm{Ce$$^{4+}$$} + \mathrm{Mn$$^{3+}$$} \rightarrow \mathrm{Ce$$^{3+}$$} + \mathrm{Mn$$^{4+}$$}$$
Step 3: $$\mathrm{Tl^+} + \mathrm{Mn$$^{4+}$$} \rightarrow \mathrm{Tl$$^{3+}$$} + \mathrm{Mn$$^{2+}$$}$$
Which species is an intermediate?

Accepted Answer

$$\mathrm{Mn$$^{3+}$$}$$

Question 13

Which of the following best describes how a catalyst increases the rate of a reaction?

Accepted Answer

It provides an alternative pathway with lower activation energy.

Question 14

For the generic rate law $$	ext{Rate} = k[A]^x[B]^y$$, which parameter is affected by the presence of a catalyst?

Accepted Answer

The rate constant $$k$$

Question 15

Given the following $$K_p$$ values at $$500\ \mathrm{K}$$, which reaction has the greatest tendency toward product formation?
1) $$2\mathrm{NOCl} ightleftharpoons 2\mathrm{NO} + \mathrm{Cl_2$}$$, $$K_p = 1.7 	imes 10$$^{-2}$$
2) $$\mathrm{N_2O_4} ightleftharpoons 2\mathrm{$$NO_2$$}$$, K_p = 1.5$$ 	imes $$10^3
3$$) $$2\mathrm{SO_3$} ightleftharpoons 2\mathrm{SO_2$} + \mathrm{O_2$}$$, $$K_p = 1.3 	imes 10$$^{-5}$$
4) 2$$\mathrm{$$NO_2$$} ightleftharpoons 2\mathrm{NO} + \mathrm{$$O_2$$}$$, K_p = 5.9$$ 	imes $$10^{-5}$$

Accepted Answer

Reaction 2

Question 16

For the reaction $$\mathrm{SO_3$(g)} ightleftharpoons \frac{1}{2}\mathrm{O_2$(g)} + \mathrm{SO_2$(g)}$$, $$K_c = 7.7 	imes 10$$^{-4}$$. What is K_c$ for 2$$\mathrm{$$SO_2(g$$)} + \mathrm{$$O_2(g$$)} ightleftharpoons 2\mathrm{$$SO_3(g$$)}$$?

Accepted Answer

$$K_c = (7.7 	imes 10$$^{-4}$$)^{-2}$

Question 17

A student is studying the decomposition of a compound and finds that a plot of $$\ln [A] vs. $$time is linear. What is the order of the reaction?

Accepted Answer

First order

Question 18

If the rate law for a reaction is $$	ext{Rate} = k[A][B]^2$$, what will happen to the rate if $$[A] is $$doubled and $$[B] is $$tripled?

Accepted Answer

The rate will increase by a factor of 18.

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