MATH ANSWERS
More Equilibrium Constants Practice!
ICE, ICE Baby!
I.
Using the Equilibrium Constant
1.
Based on the value of Kc, determine whether the reaction favors the products, the reactants,
or neither.
2.
a)
N2 (g) + O2 (g)
b)
C2H4 (g) + H2 (g)
c)
2 NO (g) + 2 H2 (g)
d)
CO2 (g) + C (s)
2 NO (g)
Kc = 4.6 x 10-31
C2H6 (g)
Kc = 1.3 x 1021
N2 (g) + 2 H2O (g)
2 CO (g)
Kc = 6.5 x 10113
Kc = 1.17
Hydrogen fluoride, HF, decomposes according to the following equation:
2 HF (g)
H2 (g) + F2 (g)
 The value of Kc at room temperature is 1.0 x 10-95. Do you think the decomposition
occurs to any great extent at room temperature?
 If an equilibrium mixture in a 1.0 L vessel contains 1.0 mol HF, what is the amount
of H2 formed? Does this result agree with your previous answer?
3.2 x 10-48 mol H2
3.
The following reaction has Kc = 3.07 x 10-4 at 24°C: 2 NOBr (g)
2 NO (g) + Br2 (g)
For each of the following reaction compositions, decide whether the reaction is at
equilibrium, or if it is not, which way the reaction will go. *Calculate Q, compare to Kc!
a) [NOBr] = 0.0720 M, [NO] = 0.0162 M, [Br2] = 0.0123 M
Q = 6.22 x 10-4
b) [NOBr] = 0.103 M, [NO] = 0.0134 M, [Br2] = 0.0181 M
Q = 3.06 x 10-4
c) [NOBr] = 0.121 M, [NO] = 0.0159 M, [Br2] = 0.0139 M
Q = 2.40 x 10-4
II.
Calculating Equilibrium Constants
1.
Phosgene, COCl2, is used in the manufacturing of polyurethane plastics and is prepared
from CO and Cl2. An equilibrium mixture at 395°C contains 0.012 M CO and 0.025 M Cl2
with a Kc = 1.23 x 103. What is the [COCl2] in this equilibrium mixture?
CO (g) + Cl2 (g)
COCl2 (g)
.37 M
2.
Nitrogen monoxide, NO, is formed in automobile exhaust by the reaction of the N2 and O2
in the air. The Kc of this reaction at 2127°C is 0.0025. If an equilibrium mixture at this
temperature contains 0.023 mol N2 and 0.031 mol O2 per liter, what is the [NO]?
N2 (g) + O2 (g)
2 NO(g)
.0013 M
1.3 x 10-3 M
3.
d
The reaction of CO with H2O has Kc = 0.58 at 1000°C and is used to increase the ratio of
hydrogen in synthesis gas. Suppose you start with 1.00 mol of CO and 1.00 mol H2O in a
50.0 L vessel. How many moles of each substance are in the equilibrium mixture at
1000°C?
CO (g) + H2O (g)
CO2 (g) + H2 (g)
CO and H2O = 0.57 mol
CO2 and H2 = 0.43 mol
4.
Iodine and bromine react to create iodine monobromide, IBr. What is the equilibrium
composition, in both moles and Molarity, of a mixture at 150°C that initially contained
0.15 mol each of both iodine and bromine in a 5.0 L vessel? Kc = 120 at this temperature.
I2 (g) + Br2 (g)
2 IBr (g)
I2 and Br2 = .005 M and .025 mol
IBr = .05 M and .25 mol
5.
Hydrogen and iodine react to produce hydrogen iodide. Suppose 1.00 mol H2 and
2.00 mol I2 are placed in a 1.00 L vessel at 458°C. How many moles of substances are
in the gaseous mixture when it comes to equilibrium at this temperature? (Kc = 49.7)
H2 (g) + I2 (g)
2 HI (g)
H2 = .07 mol
I2 = 1.07 mol
HI = 1.86 mol
6.
Calculate the composition of the gaseous mixture obtained when 12.5 mol of CO2 is exposed
to hot carbon at 800°C in a 2.00 L vessel. Kc = 14.0 for this reaction at this temperature.
CO2 (g) + C (s)
2 CO (g)
CO2 = 6.02 mol
CO = 13.0 mol