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This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. V1:1, V2:1, V3:1, V4:1, V5:2. You will have 20 minutes for the quiz. Please make sure you write your version num- bers on your scantron. Good luck!
Mlib 07 1133 21:02, general, multiple choice, > 1 min, fixed. 001 (part 1 of 1) 5 points What would be the expression for Kc for the reaction
4 NH 3 (g) + 5 O 2 (g) ⇀↽ 4 NO(g) + 6 H 2 O(g)
at equilibrium?
- [NO]^4 [H 2 O]^6
- [NH 3 ]^4 [O 2 ]^5
[NO]^4 [H 2 O]^6
[NH 3 ]^4 [O 2 ]^5
correct
[NH 3 ]^4 [O 2 ]^5
[NO]^4 [H 2 O]^6
[NO]^4 [H 2 O]
[NH 3 ]^4
Explanation:
Msci 17 0514 21:11, general, multiple choice, > 1 min, fixed. 002 (part 1 of 1) 5 points Kc = 2. 6 × 108 at 825 K for the reaction
2 H 2 (g) + S 2 (g) ⇀↽ 2 H 2 S(g)
The equilibrium concentration of H 2 is 0. M and that of S 2 is 0.0010 M. What is the equilibrium concentration of H 2 S?
- 10 M
- 1.02 M correct
- 0.10 M
- 0.0010 M
Explanation: Kc = 2. 6 × 108 [H 2 ]eq = 0.0020 M [S 2 ]eq = 0.0010 M
2 H 2 (g) + S 2 ⇀↽ 2 H 2 S
Kc =
[H 2 S]^2
[H 2 ]^2 [S 2 ]
[H 2 S] =
Kc [H 2 ]^2 [S 2 ]
=
(2. 6 × 108 ) (0.0020 M)^2 (0.0010 M)
= 1.0 M
Msci 17 0503 21:11, general, multiple choice, > 1 min, fixed. 003 (part 1 of 1) 5 points Suppose the reaction
A ⇀↽ B has an equilibrium constant of 1.0 and the ini- tial concentrations of A and B are 0.5 M and 0.0 M, respectively. Which of the following is the correct value for the final concentration of A?
- 0.500 M
- 0.250 M correct
- 1.00 M
- 1.50 M
- None of these is correct. Explanation: K = 1. 0 [A]ini = 0.5 M [B]ini = 0 M A ⇀↽ B ini, M 0.5 0. ∆, M −x x eq, M 0. 5 − x x
K =
[B]
[A]
x
- 5 − x
x = 0.25 M
[A] = 0. 5 − x = 0.25 M
Msci 17 0509 21:11, general, multiple choice, > 1 min, fixed. 004 (part 1 of 1) 5 points The equilibrium constant for the gaseous re- action
CO + H 2 O ⇀↽ CO 2 + H 2
is 4.0 at a certain temperature. A reaction is carried out at this temperature starting with 2.0 mol/L of CO and 2.0 mol/L of H 2 O. What will be the equilibrium concentration of H 2?
- 2.0 M
- 0.75 M
- 1.33 M correct
- 0.67 M
- 1.5 M
Explanation: K = 4. 0 [CO]ini = 2.0 mol/L [H 2 O]ini = 2.0 mol/L
CO + H 2 O ⇀↽ CO 2 + H 2
Ini, M 2 2 − − ∆, M −x −x +x +x Final, M 2 − x 2 − x x x
Subsitute the final concentrations into the equation for K:
K =
[CO 2 ] [H 2 ]
[CO] [H 2 O]
(x) (x) (2 − x) (2 − x)
4 =
x^2 4 − 4 x + x^2 x^2 = 4(4 − 4 x + x^2 ) = 16 − 16 x + 4x^2 03 x^2 − 16 x + 16
Solving the quadratic equation,
x = 1.33 or x = 4
Since all of the ratios in the reaction are one to one, you cannot end up with a greater number of moles of H 2 than 2 mol/L, so the correct value of x must be 1.33 M.
ChemPrin3e T09 44 21:10, general, multiple choice, < 1 min, fixed. 005 (part 1 of 1) 5 points The equilibrium constant Kc for the reaction
2 SO 2 (g) + O 2 (g) → 2 SO 3 (g)
is 11.7 at 1100 K. A mixture of SO 2 , O 2 , and SO 3 , each with a concentration of 0.015 M, was introduced into a container at 1100 K. Which of the following is true?
- SO 2 (g) and O 2 (g) will be formed until equilibrium is reached. correct
- [SO 3 ] = 0.045 M at equilibrium.
- [SO 3 ] = 0.015 M at equilibrium.
- SO 3 (g) will be formed until equilibrium is reached.
- [SO 3 ] = [SO 2 ] = [O 2 ] at equilibrium.
Explanation:
Mlib 06 0003 21:15, general, multiple choice, > 1 min, fixed. 006 (part 1 of 1) 5 points For the system
H 2 (g) + CO 2 (g) ⇀↽ H 2 O(g) + CO(g)
at equilibrium, the addition of H 2 (g) would cause (according to LeChatelier’s principle)
- only more H 2 O(g) to form.
- only more CO(g) to form.
- more H 2 O(g) and CO(g) to form. cor- rect
- only more CO 2 (g) to form.
