Exam 1 Review
Supplemental Instruction
Iowa State University
Leader: Lindsey
Course: CHEM 178
Instructor:
Date: 9/16/15
Free Response
CH. 14
1. A chemical reaction that has a very large rate constant should be expected to have a
relatively low value of this energy. _______________
2. For the reaction 2𝐻2 (𝑔) + 2𝑁𝑂(𝑔) → 𝑁2 (𝑔) + 2𝐻2 𝑂(𝑔)
a. Write the relationship between the rate of disappearance of NO and the rate of
appearance of N2.
b. What is the rate law if the reaction is first order with respect to H2 and second
order with respect to NO?
3. Using the rate law expression found in question 2, predict the effect if:
a. The concentration of NO is doubled
b. The concentration of NO is reduced by two-thirds
c. The temperature is reduced
4. Given the following data for the reaction 𝐶𝐹4 (𝑔) + 𝐻2 (𝑔) → 𝐶𝐻𝐹3 (𝑔) + 𝐻𝐹(𝑔)
determine the rate law for the reaction.
[CF3] initial (M)
[H2] initial (M)
Rate (M/s)
0.10
0.10
45
0.15
0.10
67.5
0.20
0.20
180
0.20
0.30
270
5. An alteration in the structure of a certain virus follows first-order kinetics with an
activation energy of 587 kJ/mol. The half-life of the reaction at 29.60C is 1.62x104 s (1 yr
= 3.154x107s). What are the rate constant at 29.60C and the half-life at 320C for the
alteration of structure of the virus?
CH. 15
1. Write Kc expressions for the following reactions:
a. 𝐶𝑙2 (𝑔) ⇔ 𝐶𝑙2 (𝑙)
b. 𝐴𝑔2 𝑆𝑂4 (𝑠) ⇔ 2𝐴𝑔+ (𝑎𝑞) + 𝑆𝑂42− (𝑎𝑞)
c. 𝐶3 𝐻6 (𝑔) + 𝐻2 (𝑔) ⇔ 𝐶3 𝐻8 (𝑔)Cl2 (g) ⇔ Cl2 (l)
d. 2𝐶3 𝐻6 (𝑔) + 9𝑂2 (𝑔) ⇔ 6𝐻2 𝑂(𝑙) + 6𝐶𝑂2 (𝑔)
2. A closed container at 250C is charged with N2O4 a partial pressure of 0.54 atm, and
NO2 at a partial pressure of 0.50 atm at equilibrium. What is Kp? 2𝑁𝑂2 (𝑔) ⇔ 𝑁2 𝑂4 (𝑔)
3. What is the value of the equilibrium constant for the reaction 2 NO2(g)
100o C?
N2O4(g)
2 NO2(g) Kc = 0.212 @ 100oC
4. Calculate the value of Kc for the reaction: 2 N2O(g) + 3 O2(g)
following information.
Equation
2 N2O4(g), using the
Equilibrium Constant
2 N2 (g) + O2(g)
N2O4(g)
N2O4(g) at
2 N2O(g)
2 NO2(g)
½ N2(g) + O2(g)
NO2(g)
Kc = 1.2 x 10-35
Kc = 4.6 x 10-3
Kc = 4.1 x 10-9
Multiple Choice
1. A catalyst increases the rate of a reaction by doing which of the following?
a. Increasing reactant concentrations
b. Increasing temperature
c. Decreasing temperature
d. Increasing activation energy of a reaction
e. Decreasing activation energy of a reaction
2. Given the following mechanism for a reaction:
Cl2(g)  2Cl(g)
2NO(g) + 2Cl(g)  N2(g) + 2 ClO(g)
2ClO(g)  Cl2(g) + O2(g)
Which of the following is a catalyst in the reaction?
a. Cl2
b. N2O5
c. N2
d. ClO
e. O2
3. What are the units of k for the rate law Rate=k[A][B]2 when the concentration unit is
mol L-1?
a. s-1
b. s
c. L mol-1 s-1
d. L2 mol-2 s-1
e. L2 – s2 mol-2
4. The type of chemical equilibrium exemplified by the following reaction is:
BaSO4(s) ⇌ BA2+(aq) + SO42-(aq)
a. Chemical equilibrium
b. Haber
c. Heterogeneous
d. Homogeneous
e. Mass action
5. The position of equilibrium for the reaction
ZnO(s) + H2(g) ⇌ Zn(s) + H2O(g)
does not depend upon which of the following: (1) concentration of ZnO(s); (2)
concentration of H2(g); (3) concentration of Zn(s); (4) concentration of H2O(g); (5)
the value of Kc?
a. (1), (2), (5)
b. (2), (3), (5)
c. (1), (3)
d. (2), (4)
e. (5)
6. Which statement about catalysts and equilibrium is correct?
a. A catalyst does not appear in a rate equation; thus it does not affect the
equilibrium.
b. A catalyst finds a new mechanistic pathway that affects concentrations
differently.
c. A catalyst affects the rates of the forward and reverse reactions equally; thus,
there is no net change in concentrations.
d. Solid catalysts, which are common in several industrial applications, would not
affect the equilibrium constant since solids do not appear in the equilibriumconstant expression.
e. A different and unique catalyst is needed for every equilibrium at different
temperatures.
7. What is the value of Kc for the following reaction if the equilibrium concentrations are
[A] = 0.60 M [B] = 0.35 M [C] = 0.55 M?
2 A (aq) + B (aq) ⇌ 2 C (aq)
a. 0.38
b. 0.42
c. 2.40
d. 2.62