kinetics apmc

Questions 1-2 H3AsO4 + 3I− + 2 H3O+H3AsO3 + I3 + H2O The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry shown above. The experimental rate law of the reaction is: Rate = k [H3AsO4] [I−] [H3O+] 1. What is the order of the reaction with respect to I−? (A) 1 (B) 2 (C) 3 (D) 5 (E) 6 2. According to the rate law for the reaction, an increase in the concentration of hydronium ion has what effect on this reaction? (A) The rate of reaction increases. (B) The rate of reaction decreases. (C) The value of the equilibrium constant increases. (D) The value of the equilibrium constant decreases. (E) Neither the rate nor the value of the equilibrium constant is changed.

(A) 1 (A) The rate of reaction increases.

14. 2 NO(g) + O2(g) → 2 NO2(g) A possible mechanism for the overall reaction represented above is the following: (1) NO(g) + NO(g) → N2O2(g) slow (2) N2O2(g) + O2(g) → 2NO2(g) fast Which of the following rate expressions agrees best with this possible mechanism? (A) Rate = k[NO]2 (D) Rate = k[NO]2 [O2] (B) Rate = k[NO] (E) Rate = k[N2O2][O2][O2] (C) Rate = k[NO]2[O2]

(A)Rate=k[NO]2

9. The isomerization of cyclopropane to propylene is a first-order process with a half-life of 19 minutes at 500 °C. The time it takes for the partial pressure of cyclopropane to decrease from 1.0 atmosphere to 0.125 atmospheres at 500 °C is closest to... (A) 38 minutes (B) 57 minutes (C) 76 minutes (D) 152 minutes (E) 190 minutes

(B) 57 minutes

Step 1:Ce4+Mn2→Ce3+Mn3 Step 2:Ce4+Mn3→Ce3+Mn4 Step 3:Mn4+Tl→Tl3+Mn2 8. The proposed steps for a catalyzed reaction between Ce4+ and Tl+ are represented above. The products of the overall catalyzed reaction are... (A) Ce4+ and Tl+ (B) Ce3+ and Tl3+ (C) Ce3+ and Mn3+ (D) Ce3+ and Mn4+ (E) Tl3+ and Mn2+

(B) Ce3+ and Mn3+

5. rate = k[X] For the reaction whose rate law is given above, a plot of which of the following is a straight line? (A) [X] versus time (B) ln [X] versus time (C) 1/[X] versus time (D) [X] versus 1/time (E) ln [X] versus 1/time

(B) ln [X] versus time

6. (CH3)3CCl(aq) + OH− → (CH3)3COH(aq) + Cl− For the reaction represented above, the experimental rate law is given as follows: Rate = k [(CH3)3CCl] If some solid sodium solid hydroxide is added to a solution that is 0.010-molar in (CH3)3CCl and 0.10-molar in NaOH, which of the following is true? (Assume the temperature and volume remain constant.) (A) Both the reaction rate and k increase. (B) Both the reaction rate and k decrease. (C) Both the reaction rate and k remain the same. (D) The reaction rate increases but k remains the same. (E) The reaction rate decreases but k remains the same.

(C) Both the reaction rate and k remain the same.

3. 2 A(g) + B(g) ⇄ 2 C(g) When the concentration of substance B in the reaction above is doubled, all other factors being held constant, it is found that the rate of the reaction remains unchanged. The most probable explanation for this observation is that... (A) the order of the reaction with respect to substance B is 1. (B) substance B is not involved in any of the steps in the mechanism of the reaction. (C) substance B is not involved in the rate-determining step of the mechanism, but is involved in subsequent steps. (D) substance B is probably a catalyst, and as such, its effect on the rate of the reaction does not depend on its concentration. (E) the reactant with the smallest coefficient in the balanced equation generally has little or no effect on the rate of the reaction.

(C)substance B is not involved in the rate-determining step of the mechanism, but is involved in subsequent steps.

7. Relatively slow rates of chemical reaction are associated with which of the following? (A) The presence of a catalyst (B) High temperature (C) High concentration of reactants (D) Strong bonds in reactant molecules (E) Low activation energy

(D) Strong bonds in reactant molecules

16. Which of the following must be true for a reaction for which the activation energy is the same for both the forward and the reverse reactions? (A) A catalyst is present. (B) The reaction order can be obtained directly from the balanced equation. (C) The reaction order is zero. (D) ΔH° for the reaction is zero. (E) ΔS° for the reaction is zero.

(D) ΔH° for the reaction is zero.

Step 1) N2H2O2 ⇄ N2HO2 + H (fast equilibrium) Step 2) N2HO2− → N2O + OH (slow) Step 3) H+ OH → H2O (fast) 4. Nitramide, N2H2O2, decomposes slowly in aqueous solution. This decomposition is believed to occur according to the reaction mechanism above. The rate law for the decomposition of nitramide that is consistent with this mechanism is given by which of the following? (A) Rate = k [N2H2O2] (B) Rate = k [N2H2O2] [H+] (C) Rate = (k [N2H2O2]) / [H+] (D) Rate = (k [N2H2O2]) /[N2HO2] (E) Rate = k [N2H2O2] [OH−]

C)Rate= (k [N2H2O2])/[H]