Equilibrium Problem Set 1
Name______________________________
Equilibrium Concepts and Equilibrium Expressions
Period _______
Date _____________
Conceptual Equilibrium (7 points)
1.
The following diagrams represent a hypothetical reaction A  B, with A represented by black spheres and B
represented by white spheres. The sequence from left to right represents the system as time passes. Do the
diagrams indicate the system reaches an equilibrium state? Explain.
1 point
2.
Consider an initial mixture of N2 and H2 gases that can be represented as follows:
The gases react to form ammonia gas (NH3) as represented by the following concentration profile:
2 points
3.
a.
Label each plot on the graph as N2, H2, or NH3, and explain your answers.
b.
Explain the relative shapes of the plots.
c.
When is equilibrium reached? How do you know?
Can the equilibrium constant ever be a negative number? Explain.
1 point
4.
1 point
When the following reactions come to equilibrium, does the equilibrium mixture contain mostly reactants or
mostly products?
Kc = 1.5 x 10-10
a. N2 (g) + O2 (g)  2 NO (g)
b.
2 SO2 (g) + O2 (g)  2 SO3 (g)
Kc = 2.5 x 109
5.
Suppose a reaction has the equilibrium constant K = 1.3 x 108. What does the magnitude of this constant tell you
about the relative concentrations of products and reactants that will be present once equilibrium is reached?
Compare the rate constants of the forward and reverse reaction – are they the same or is one larger? Which one?
2 points
6.
The following diagram represents an equilibrium mixture produced a reaction of the type A + X  AX. If the
volume is 1 L, is K greater than or smaller than 1? Justify numerically.
2 points
Writing Equilibrium Expressions (3 points)
7. Write the equilibrium expression (K) for each of the following gas-phase reactions:
a. N2 (g) + O2 (g)  2 NO (g)
1 point
b.
N2O4 (g)  2 NO2 (g)
c.
SiH4 (g) + 2 Cl2 (g)  SiCl4 (g) + 2 H2 (g)
d. 2 PBr3 (g) + 3 Cl2 (g)  2 PCl3 (g) + 3 Br2 (g)
8.
Write the expression for Kc for the following reactions. In each case, indicate whether the reaction is a
homogeneous or heterogeneous equilibrium.
a. 3 NO (g)  N2O (g) + NO2 (g)
b. CH4 (g) + 2 H2S (g)  CS2 (g) + 4 H2 (g)
2 points
c. Ni(CO)4 (g)  Ni (s) + 4 CO (g)
d. HF (aq)  H+ (aq) + F- (aq)
9.
The following diagram represents a reaction shown going to completion.
a.
Letting A = white spheres and B = black spheres, write a balanced equation for the reaction based on the
reactants that are being consumed and the products that being made.
b.
Write the equilibrium-constant expression for the reaction.
3 points
Manipulations of K (2 points)
10. Consider the following equilibrium, for which Kp = 0.0752 at 480°C:
2 Cl2 (g) + 2 H2O (g)  4 HCl (g) + O2 (g)
a. What is the value of Kp for the reaction 4 HCl (g) + O2 (g)  2 Cl2 (g) + 2 H2O (g)?
1 point
b.
What is the value of Kp for the reaction Cl2 (g) + H2O (g)  2 HCl (g) + ½ O2 (g)?
1 point
11. Calculate a value for the equilibrium constant for the reaction O2 (g) + O (g)  O3 (g)
K = 6.8 x 10-49
NO2 (g)  NO (g) + O (g)
O3 (g) + NO (g) NO2 (g) + O2 (g)
K = 5.8 x 10-34
1 point
given: