17.1 a) APPLICATION OF EQUILBRIUM LAW (CALCULATIONS)
*CALCULATING EQUILIBRIUM CONCENTRATIONS (USING AN “ICE” TABLE)
I = ______________ __________________ of reactant and products (before reaction)
C = _____________ ___ _________________ of reactants and products between the start and the point at
which equ’m is achieved
E = _____________ of reactants and products at ___________________
**Concentration units must be: mol dm-3 (equivalent units  M…or mol/L)
Example: Consider the following equilibrium:
H2(g) + F2(g)
2HF(g) + energy
*Try the following:
a) At a temperature of 308 K, hydrogen and fluorine both have an initial concentration of 1.00 mol dm-3. Once a state
of dynamic equilibrium is established, the concentration of fluorine is determined to be 0.24 mol dm-3. Determine
the equilibrium concentrations of the other entities in the system.
b) Determine the percent reaction.
c) Sketch a concentration-time graph that represents this system from time = 0 seconds to time = 60 seconds.
Assume equilibrium is established at the 40 second mark.
d) Write the equilibrium constant expression for the system and then determine its magnitude at 308 K.
e) How would the magnitude of Kc be affected if a catalyst were used? Explain.
f) Determine the magnitude of Kc for the reverse reaction at 308 K.
g) Would the magnitude of Kc increase or decrease at a temperature of 400 K? Explain.
h) How would an increase in pressure affect this equilibrium system? Explain.
*Start by constructing an “RICE” table as follows:
Reaction
H2(g)
+
F2(g)
Initial
Change
Equilibrium
2HF(g)
MORE PRACTICE:
1. The esterification reaction between ethanol and ethanoic acid produces the ester, ethyl ethanoate, and water.
1.0 mol of ethanol and 1.0 mol of ethanoic acid are dissolved in an inert organic solvent to produce 1 dm3 of the
solution and heated in the presence the catalyst, sulfuric acid. When equilibrium is reached 0.60 mol of each
reactant remains. Calculate the equilibrium constant, Kc.
2. Sulfur dioxide, SO2, is oxidized in the presence of the catalyst vanadium(V) oxide, V2O5. In this reaction 2.0
mol of SO2 and 1.4 mol of O2 are mixed in a 3.0 dm3 sealed container and the system is allowed to come to
equilibrium. At 700 K a conversion rate of 15% is achieved. Calculate the equilibrium constant for this reaction.
3. When carbon dioxide is heated in a closed container, it decomposes into carbon monoxide and oxygen
according to the following equilibrium equation: 2CO2(g)
2CO(g) + O2(g)
When 2.0 mol of CO2(g) is placed in a 5.0 L closed container and heated to a particular temperature, the
equilibrium concentration of CO2(g) is measured to be 0.39 mol dm-3. Determine the equilibrium concentrations
of the other entities in the system.
4. Consider the following equilibrium system: CO(g) + 2H2(g)
CH3OH(g)
The initial concentration of methanol is 4.0 mol dm-3; at equilibrium its concentration is 1.5 mol dm-3.
Determine the concentrations of the other entities at equilibrium.
5. Consider the following equilibrium system: N2(g) + 3H2(g)
2NH3(g) Kc = 626 @ 200°C
The equilibrium concentrations of hydrogen and nitrogen are 0.50 mol dm-3 and 0.46 mol dm-3, respectively.
Calculate the equilibrium concentration of ammonia.
6. If 1.00 mol each of carbon dioxide and hydrogen is initially injected into a 10.0 L reaction chamber at 986°C,
what would be the concentrations of each entity at equilibrium?
CO2(g) + H2(g)
CO(g) + H2O(g)
Kc = 1.60 @ 986°C
7. If 0.50 mol of iodine and 0.50 mol of chlorine are initially placed into a 2.0 L reaction chamber at 25°C,
what would be the concentrations of each entity at equilibrium?
I2(g) + Cl2(g)
2ICl(g)
Kc = 81.9 @ 25°C
THE REACTION QUOTIENT, Q
8. Consider the following equilibrium system: PCl5(g)
PCl3(g) + Cl2(g)
Kc = 12.5 @ 60°C
A 1.0 L reaction vessel is analyzed and found to contain 3.2 mol Cl2(g), 1.5 mol PCl3(g), and 2.0 mol PCl5(g).
Show that the reaction mixture has not yet reached equilibrium.