CHEM1200

Practice Test 2

Note: These questions are representative of the types you can expect on the test. The actual test will be longer, typically between 20-40 questions.
You will need to bring a SCANTRON and pencil to each class test.
Instructions: Select the best answer then click on "get answer" box.


Question 1. For the reaction, C6H14 (g) ® C6H6 (g) + 4 H2 (g),     DP(C6H14)/D t was found to be -6.2 x 10-3 atm/sec.

Determine the value of DP(H2)/Dt at the same time.
a. 6.2 x 10-3 atm/sec
b. 1.6 x 10-3 atm/sec
c. 2.5 x 10-2 atm/sec
d. - 1.6 x 10-3 atm/sec
e. -2.5 x 10-2 atm/sec



Question 2. The reaction, A + 2 B ® products, was found to have the following rate law:    rate = [A][B]2

While holding the concentration of A constant, the concentration of B was increased three fold. Predict by what factor the rate of the reaction will increase.  
a. 3
b. 6
c. 9
d. 27
e. 30



Question 3. The units for a first-order rate constant are:
a. M/s
b. 1/M.s
c. 1/s
d. 1/M2.s



Question 4. Nitric oxide reacts with hydrogen to form nitrous oxide and water. Use the following data to determine the rate equation for the reaction.

2 NO + H2 ® N2O + H2O

Expt.#          [NO]o           [H2]o          Initial Rate
===================================
     1               0.021          0.065            1.46 M/min
     2               0.021          0.260            1.46 M/min
     3               0.042          0.065            5.84 M/min
===================================
a. rate = k[NO]
b. rate = k[NO]2
c. rate = k[NO][H2]
d. rate = k[NO]2[H2]
e. rate = k[NO]2[H2]2



Question 5. Ammonium ion (NH4+) reacts with nitrite ion (NO2-) according to the following equation:

NH4+ (aq) + NO2- (aq) ® N2 (g) + 2 H2O (l)

The following initial rates of reaction have been measured for the given reactant concentrations:

Expt.#          [NH4+]           [NO2-]          Rate (M/hr)
=====================================
     1               0.010              0.020               0.020
     2               0.020              0.020               0.040
     3               0.010              0.010               0.005
=====================================

Which of the following is the rate law (rate equation) for this reaction?
a. rate = k [NH4+][NO2-]4
b. rate = k [NH4+][NO2-]
c. rate = k [NH4+][NO2-]2
d. rate = k [NH4+]2[NO2-]
e. rate = k [NH4+]1/2[NO2-]1/4



Question 6. An increase in the temperature of the reactants causes an increase in the rate of reaction. The best explanation is: As the temperature increases
a. the collision frequency increases
b. the concentration of the reactants increases
c. the activation energy decreases
d. the activation energy increases



Question 7. Complete the statement: A catalyst
a. increases the activation energy
b. alters the reaction mechanism
c. increases the average kinetic energy of the reactants
d. increases the concentration of reactants
e. increases the collision frequency of reactant molecules



Question 8. Suppose that the reaction:    Cl2 (g) + 3 F2 (g) ® 2 ClF3 (g)
is first order in F2 and second order in Cl2. Which of the following is not true?
a. If [F2] is doubled, the rate of the reaction doubles
b. If [Cl2] is doubled, the rate of the reaction increases four fold
c. If both [F2] and [Cl2] are doubled, the rate of the reaction is increased eight fold
d. If [F2] is doubled and [Cl2] is halved, the rate of the reaction remains the same
e. The rate of the reaction is third order overall



Question 9. The equilibrium constant expression for the reaction below is:

2 BrF5 (g) ⇋ Br2 (g) + 5 F2 (g)
a. Keq = [Br2][F2]/[BrF5]
b. Keq = [Br2][F2]5/[BrF5]2
c. Keq = [Br2][F2]2/[BrF5]5
d. Keq = [BrF5]2/[Br2][F2]5
e. Keq = [BrF5]5/[Br2][F2]2



Question 10. Kc = 0.040 for the reaction below at 450oC. If a reaction begins with 0.40 mole of Cl2 and 0.20 mole of PCl3 in a 1.0 liter container, what is the concentration of Cl2 at equilibrium?

PCl3(g) + Cl2(g) ⇋ PCl5(g)
a. 0.07 M
b. 0.16 M
c. 0.11 M
d. 0.04 M
e. 0.26 M



Question 11. At 700 K, the reaction: 2 SO2 (g) + O2 ⇋ 2 SO3 (g)

has an equilibrium constant Kc = 4.3 x 106, and the following concentrations are present:

[SO2]eq = 0.010 M       [SO3]eq = 10 M      [O2]eq = 0.010 M

Is the mixture at equilibrium, yes or no? If not at equilibrium, in which direction, left to right, or right to left, will reaction occur to reach equilibrium?
a. Yes
b. No, left to right
c. No, right to left
d. there is not enough information to tell



Question 12. For the following reaction at equilibrium, which one of the changes below would cause the equilibrium to shift to the left?

2 NOBr (g) ⇋ 2 NO (g) + Br2 (g)          DHo = 30 kJ
a. increase the container volume
b. remove some NO
c. remove some Br
d. add more NOBr
e. decrease the temperature



Question 13. Consider the following equilibrium system:

PCl5 ⇋ PCl3 + Cl2        DHo = +87.8 kJ

Which of the following statements is false?
a. Increasing the concentration of PCl5 causes the system to reach an equilibrium that has more product
b. Increasing the temperature shifts the equilibrium to the right
c. A catalyst speeds up the approach to equilibrium and shifts the position of equilibrium to the left
d. When the total pressure of the system is decreased, the equilibrium is shifted to the right
e. Increasing the temperature causes the equilibrium constant to increase