Equilibrium – Cumulative Problems
1. At 633C, 3.60 mole of ammonia are placed in a 2.00 L vessel and allowed to decompose to the elements:
2NH3(g)
N2(g) + 3 H2(g) If Kc = 6.56 x 10-3 for this reaction at this temperature, calculate the equilibrium
concentration of each reagent.
2. Nitrogen, hydrogen and NH3 are in t equilibrium in a 1.00L container: N2(g) + 3 H2(g)
2NH3(g) where the H =
+68kJ. How will each of the following changes affect the indicated quantities? Write increases, decreases or no change.
CHANGE
[H2]
[NH3]
Kc
a) Some H2 is added to the container
b) The temperature of the gases in the container is increased
c) Partial pressure of NH3 is increased
d) Volume of the flask increases
3. The Kp for the following reaction is 0.16 at 25C. The enthalpy change for the reaction at standard conditions is -344kJ.
2NOBr(g)
2NO(g) + Br2(g) Predict the effect of the following changes on the position of the equilibrium: state
which way the equilibrium will shift (left, right, no change) when each of the following changes is made.
a) Addition of more Br2(g)
b) Removal of some NOBr(g)
c) Increase in the container volume
d) Decrease in the temperature
4. Consider the n-butane
isobutene system where kc = 2.5 The system is originally at equilibrium with [n] = 1.0M
[iso] = 2.5M.
a) If 0.50M of isobutene is suddenly added and then the system shifts to a new equilibrium position, what are the
equilibrium concentrations of each gas?
b) If 0.50M of n-butane is added and the system shifts to a new equilibrium position, what are the equilibrium
concentrations of each gas?
5. The decomposition of ammonium hydrogen sulfide at 25C is: NH4HS(s)
NH3(g) + H2S(g) The Kp for this
decomposition at 25C is 0.11.
a) When the pure salt decomposes in a flask, what are the equilibrium pressures of NH3 and H2S?
b) If NH4HS is placed in a flask already containing 0.50atm of NH3 and then the system is allowed to come to equilibrium,
what are the equilibrium pressures of NH3 and H2S?
c) Do your results in parts a) and b) conform to LeChatelier’s Principle?
6. The equilibrium constant, Kc, for the decomposition of COBr2 is 0.190 at 73C.
COBr2(g)
CO(g) + Br2(g)
a) If 1.50 mol of COBr2 are placed in a 2.00 L flask and heated to 73C, what are the equilibrium concentrations of each
compound?
b) If 1.00 mol of CO is added to the system at equilibrium, what are the concentrations of each compound after
equilibrium is reestablished?
7. The equilibrium constant, Kp=0.087at 300Cfor the formationofPCl5 fromPCl3andCl2.
PCl3(g) + Cl2(g)
PCl5(g) If you place1.0molefo each reactant in a5.0Lflask and heat to 300C, what is the
maximum concentration of PCl5 that can exist at equilibrium?
8. At 1800K,oxygen dissociates very slightly into its atoms: O2(g)
2O(g) Kp = 1.7 x 10-8 If you place 1.0 mol of
O2 in a 10.0 L vessel and heat it to 1800K, how many O atoms are present in the flask?