Chem Midterm # 1

A reaction is found to have an activation energy of 108 kJ/mol. If the rate constant for this reaction is 4.60 x 10-6 s-1 at 275 K, what is the rate constant at 366 K?

A) 1.85 x 10-4 s^-1
B) 0.580 s^-1
C) 5.40 x 10-5 s^-1
D) 1.72 s^-1
E) 11.7 s^-1

Which of the following statements is FALSE?
A) The average rate of a reaction decreases during a reaction.
B) The half life of a first order reaction is dependent on the initial concentration of reactant.
C) It is not possible to determine the rate of a reaction from its balanced equation.
D) None of the statements is false.
E) Zero order reactions are not dependent on concentration.

Note if you chose “a”, that is acceptable since in the case of zero order reaction that statement is false,
and it does not specify the reaction order.

Which of the following reactions would you predict to have the smallest orientation factor?
A) X₂ + Y₂ >> 2 XY
B) N + O₂ >> NO₂
C) NOCl₂ + NO >> 2 NOCl
D) All of these reactions should have nearly identical orientation factors.
E) N₂ + O2 >> 2 NO

What is the overall order of the following reaction, given the rate law?
2 X + 3 Y >> 2 Z Rate =k[X]¹[Y]²
a) 3^rd order
b) 5^th order
c) 2^nd order
d) 1^st order
e) 0^th order

Consider the following reaction, equilibrium concentrations, and equilibrium constant at a particular
temperature. Determine the equilibrium
concentration of H2O(g).
C₂H₄(g) + H₂O(g) ↔ C₂H₅OH(g) Kc = 9.0 x 10³
[C₂H₄]_eq = 0.015 M [C₂H₅OH]_eq = 1.69 M
A) 1.0 M
B) 9.9 x 10^-7 M
C) 0.013 M
D) 1.68 M
E) 80. M

What are the units of k in the following rate law?
Rate = k[X]2[Y]
a) 1 Ms²
b) 1 M²s
c) M²s
d) M²s
e) 1 M³s

The first-order decomposition of cyclopropane has a rate constant of 6.7 x 10^-4 s^-1. If the initial
concentration of cyclopropane is 1.33 M, what is the concentration of cyclopropane after 644 s?
A) 0.43 M
B) 0.15 M
C) 0.94 M
D) 0.86 M
E) 0.67 M

The first-order rearrangement of CH₃NC is measured to have a rate constant of 3.61 x 10^-15 s^-1 at 298 K and a rate constant of 8.66 x 10^-7 s^-1 at 425 K. Determine the activation energy for this reaction.
A) 240. kJ/mol
B) 160. kJ/mol
C) 338 kJ/mol
D) 417 kJ/mol
E) 127 kJ/mol

Write a balanced chemical equation that corresponds to the following equilibrium constant expression.
K = [F-][H3O+]
[HF]
A) HF(aq) ↔ F^-(aq) + H₃O⁺(aq)
B) F^-(aq) + H₃O⁺(aq) ↔ HF(aq)
C) H⁺(aq) + OH^-(aq) ↔ H₂O(l)
D) F^-(aq) + H₃O⁺(aq) ↔ HF(aq) + H₂O(l)
E) HF(aq) + H₂O(l) ↔ F^-(aq) + H₃O⁺(aq)

Given the following rate law, how does the rate of reaction change if the concentration of Y is doubled?
Rate = k[X][Y]²
A) The rate of reaction will decrease by a factor of 2.
B) The rate of reaction will remain unchanged.
C) The rate of reaction will increase by a factor of 2.
D) The rate of the reaction will increase by a factor of 4.
E) The rate of reaction will increase by a factor of 5.