CHEM 1202 Sect 1 & 5
EXAM 1 Equilbrium
Spring 2014
Dr. Kolniak
FORM 1
IMPORTANT: On the SCANTRON SHEET FILL IN YOUR NAME and STUDENT NUMBER IN THE BOX’s
and BUBBLE in the corresponding letter/numbers. Ask a question if you are not sure about what to do
on a question or you are confused about the content of the question.
Select the best answer (4pts each). R = 0.0821 Latm/molK
1.
The generic reaction reaches equilibrium at 25C.
W (g) + 2 X (g)
Y (g) + 2 Z (g)
At EQUILIBRIUM it is found that:[W] = 2.0 M, [X] = 3.0 M, [Y] = 4.0 M and [Z] = 5.0 M.
What is the value of KC at this temperature?
a.
b.
c.
d.
e.
3.33
0.180
5.56
16.7
0.300
2.
Which of the following expressions is the correct equilibrium-constant expression for the
following reaction?
CO2 (g) + 2H2 (g)
a.
b.
c.
d.
e.
CH3OH 
CO2 
CH3OH 
CO2  H 2 
2
CO2  H 2 
CH3OH 
CO2  H 2 
CH3OH 
CH3OH 
2
CO2  H 2 
CH3OH (g)
3.
A sample of the following reaction mixture was found to contain: 2.0 M of A, 2.0 M of B
and 3.0 M of C. What is the algebraic expression that describes the equilibrium
concentration for C?
2 A (g) + B (g)
2 C (g)
Kc 10 at some temperature
a.
b.
c.
d.
e.
2x
3.0 + 2x
3.0 – 2x
3.0 – x
3.0 + x
4.
What is the molar solubility of La(IO3)3, where La is a La+3, KSP = 6.00 x 10-12?
a.
b.
c.
d.
e.
6.87 x 10-4 M
2.06 x 10-3 M
1.57 x 10-3 M
1.19 x 10-3 M
6.06 x 10-5 M
5.
Consider the following reaction:
A (g)
2 B(g) + 3 C (g)
The initial concentrations for [A]=[B]=[C] = 1.0 M. When the reaction reaches equilibrium
the equilibrium concentration of [B]eq= 0.60 M. What is the equilibrium concentration
for, C?
a.
0.60 M
b.
1.6M
c.
0.20 M
d.
0.80 M
e.
0.40 M
6.
Of the following equilibria, only __________ will shift to the left in response to a decrease in
volume or increase in overall pressure.
a.
b.
c.
d.
e.
H2 (g) + Cl2 (g)
2 HCl (g)
2 SO3 (g)
2 SO2 (g) + O2 (g)
N2 (g) + 3 H2 (g)
2 NH3 (g)
4 Fe (s) + 3 O2 (g)
2 Fe2O3 (s)
2HI (g)
H2 (g) + I2 (g)
7.
If the initial concentrarion of NO is 0.5 M, what is the equilibrium concentration of NO?
Consider the KC, is 2 at some temperature.
2 NO (g)
N2 (g) + O2 (g)
a.
b.
c.
d.
e.
0.207 M
0.185 M
0.293 M
0.130 M
0.087 M
8.
The equilibrium constant for reaction I. is some value for K. The equilibrium constant, K’,
for reaction II is defined as __________.
I. SO2 (g) + (1/2) O2 (g)
II. 2SO3 (g)
SO3 (g) where K = #
2SO2 (g) + O2 (g)
K’ = ?
a.
b.
c.
d.
e.
K2
2K
1/2K
1/K2
1-K2
9.
Consider the following generic heterogeneous reaction:
A(s) + 2 B(g)
If [B]in = 2.0 M, what is the [B]eq?
a.
b.
c.
d.
0.30 M
0.60 M
0.80 M
0.40 M
e.
0.50 M
C(g)
Keq= 2
10.
The equilibrium constant for the gas phase reaction
N2 (g) + 3H2 (g)
2NH3 (g)
is Keq = 4.34 × 10-3 at 300°C. At equilibrium, __________.
a.
b.
c.
d.
e.
products predominate
reactants predominate
roughly equal amounts of products and reactants are present
only products are present
only reactants are present
11.
Initially all of the components of the below reaction start off at 1.0M. At equilibrium the
flask contained 0.5 M of C. What is the algebraic expression that describes the equilibrium
concentration for A?
4 A(g) + 3 B(g)
2 C(g) + D(g)
a.
b.
c.
d.
e.
1– x
1+x
1 + 4x
1 – 4x
4x
12.
The initial concentrations of A and B are both 1.0 M. What is the algebraic expression for
the equilibrium concentration of B? KC = something
4 A (g) + 3 B (g)
2 C (g) + 4 D (g)
a.
b.
c.
d.
e.
1.0 - 3x
3x
x
1.0 + 3x
3x +1.0
13.
Calculate the KSP for Zn(OH)2, given the the maximum concentration of
Zn+2 is 2.32 x 10-6 M.
a.
b.
c.
d.
e.
5.00 x 10-17
1.25 x 10-17
1.08 x 10-11
6.24 x 10-18
3.12 x 10-18
14.
Consider the following compounds are dissolved in water. Given their KSP’s, place the
following ionic compounds inorder of increasing solubility, beginning with the least soluble.
Compound
HgS
CaSO4
BaSO4
PbCl2
KSP
2 x 10-23
2.4 x 10-5
1.1 x 10-10
1.7 x 10-5
a.
HgS < BaSO4< PbCl2< CaSO4
b.
PbCl2< CaSO4< BaSO4< HgS
c.
CaSO4< PbCl2< BaSO4< HgS
d.
HgS < BaSO4< CaSO4 < PbCl2
e.
BaSO4< HgS < CaSO4< PbCl2
15.
What is the KP for the following reaction, if the partial pressures in an equilibrium mixture
of N2, O2 and NO at 298 K are: PN2 = 2.2 PO2 = 1.8 atm and PNO= 0.50 ?
a.
b.
c.
d.
e.
0.0630
15.8
0.126
7.92
0.250
16.
Given the following reaction:
N2 (g) + O2 (g)
Fe(OH)2 (s) + H2O (l)
2 NO (g)
Fe+2 (aq) + 2 OH- (aq)
Ksp = 8.0 x 10-16 (@ 298K
Excess Fe(OH)2 is added to an 0.1 M NaOH solution. Calculate the equilibrium
concentration of [Fe+2] under these conditions.
a.
0.05 M
b.
8.0 x10-14 M
c.
8.0 x 10-18 M
d.
8.0 x 10-15 M
e.
2.0 x 10-14 M
17.
A 5.00 g sample of NO2 (MM = 44 g/mol) is placed in a 1.00 L container and heated to
350K. The NO2 decomposes to N2 and O2. R = 0.0821 L-atm/mol-K
2 NO2 (g)
N2 (g) + 2 O2 (g)
At equilibrium the total pressure in the container is 3.60 atm. Calculate the equilibrium PO2.
a.
b.
c.
d.
e.
0.335 atm
0.168 atm
2.60 atm
0.672 atm
0.134 atm
18.
Which of the following reaction(s) at equilibrium will have equilibrium mixtures that
produce mostly Reactants?
I.
II.
III.
IV.
Keq = 1020
Keq = 1
Keq = 0.23
Keq = 2 x 10-8
a.
b.
c.
d.
e.
I only
II only
III only
IV only
III and IV only
19.
The equilibrium constant, KC, for the following reaction is 2.12 at some temperature.
A (g) + 1/3 B (g)
C (g)
What is the value of K’C reaction below:
3 A (g) + B (g)
3 C (g)
a.
b.
c.
d.
e.
9.53
6.36
0.707
257
27.9
20.
Given that the concentrations [A] = [B] = 2.0 M and [C] = 4.0 M, in comparing Q to K, what
does this information tell you about the equilibrium of the reaction?
A (g) + B (g)
a.
b.
c.
d.
e.
2 C (g)
Kc = 1
The reaction is at equilibrium.
Q<K and the reaction will proceed in the reverse direction to make more reactants.
Q>K and the reaction will proceed in the forward direction to make more products.
Q<K and the reaction will proceed in the forward direction to make more products.
Q>K and the reaction will proceed in the reverse direction to make more reactants.
21.
Which of the following reactions is AT equilibrium?
Init. Conc. 1 M
0.5 M
I.
A2 (g) + B2 (g)
Init. Conc. 0.25 M 0.10 M
II.
A (g) + B (g)
3M
2 AB (g)
0.50 M
2 C (g)
Kc = 3
Kc = 10
a.
b.
c.
d.
e.
I only
II only
All are at equilibrium.
None are at equilibrium.
Not enough information.
22.
What is the correct equilibrium expression for the following reaction:
(NH4)2Se (s)
a.
2NH3 (g) + H2Se (g)
b.
[NH3][H2Se] / [(NH4)2Se]
[(NH4)2Se] / [NH3]2[H2Se]
c.
1 / [(NH4)2Se]
d.
e.
[NH3]2[H2Se]
[NH3]2[H2Se] / [(NH4)2Se]
23.
Initially, we start with PAB = 2 atm, what will be the equilibrium PC. KP = 2 at some Temp.
2 AB (g)
C (g) + D (g)
a.
b.
c.
d.
e.
0.80 atm
0.74 atm
1.2 atm
0.67 atm
0.33 atm
24.
According to the Le Chatlier’s Principle, which of the following would shift the following
reaction to produce HBr (g)? H = -250 kJ/mol
H2 (g) + Br2 (g)
I.
II.
III.
IV.
a.
b.
c.
d.
e.
2 HBr (g)
Add more H2 & Br2 to the reaction
Remove some HBr from the reaction
Cool down the reaction
Increase the pressure on the system
I only
II only
II & III only
I, II & III only
All are would produce more HBr.
25.
What is the equilibrium concentration for [OH] from a saturated Mg(OH)2 solution, where
the Ksp (Mg(OH)2) = 1.6 x 10-12 ?
a.
b.
c.
d.
e.
1.79 x 10-6 M
2.52 x 10-4 M
5.04 x 10-4 M
1.47 x 10-4 M
1.86 x 10-4 M
26.
(BONUS) Consider the following reaction:
A (g) + B (g)
C (g) + D (g)
Kc = 2 at some temperature
The following concentrations are [A] = 1.0 M and [B] = 2.0 M then [C] = 2.0 M and
[D] = 1.0 M. What is the equilibrium concentration of [B]? Check by subs your [ ] eq into EE
compare to Kc
a.
2.00 M
b.
1.77 M
c.
1.23 M
d.
0.770 M
e.
1.54 M

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