1. The document contains 7 chemistry problems involving calculation of equilibrium constants (Keq and Kc) for various chemical reactions. 2. Problem 3 calculates Keq as 1.84x10-2 for the decomposition of HI gas into H2 and I2 gases at 425C, given the partial pressures of reactants and products at equilibrium. 3. Problem 7 involves a multiple step chemical equilibrium problem, calculating the initial and equilibrium partial pressures and concentrations of gases in a reaction between CO2, H2 and H2O, and determining the equilibrium constant Kp.

1. KEY
GENERAL CHEMISTRY-II (1412)
S.I. # 17
1. Write the Keq for the reaction:
NiCO3 (s) + 2H+ (aq)   Ni2+ (aq) + CO2(g) + H2O (l)
Keq = [CO2]
2. Write (Kc) Equilibrium constant for
AgCl (s) + 2 NH3(aq)  [Ag(NH3)2]+ (aq) + Cl- (aq)
Kc = [Ag(NH3)2+][Cl-] / [NH3]2
3. Gaseous hydrogen Iodide is placed in a closed1.0 L container at 425°C where it
partially decomposes to hydrogen and iodine. 2HI (g)  H2 (g) + I2 (g). At
equilibrium, it is found that PH I =3.53x10-3 atm and PH2 = 4.79x10-4 atm, PI2 =
4.79x10-4. What is the value of Keq at this temperature?
Keq = [H2][I2] = [4.79x10-4][4.79x10-4] = 1.84x10-2
[HI]2 [3.53x10-3]2
4. What is the value of equilibrium constant Keqif at equilibrium PH2 = 6.5x10-7 atm,
PI2 = 1.06x10-5 atm, PHI = 1.87x10-5 atm. 2HI (g)  H2 (g) + I2 (g).
Keq = PH2 PI2 = (6.5x10-7)(1.06x10-5) = 2.0x10-2
PHI2 (1.87x10-5)2
5. Calculate the equilibrium constant for the reaction below if a 3.25 L tank is
found to contain 0.343 atm O2, 0.0212 atm SO3, and 0.00419 atm SO2.
2SO3 (g)  2 SO2 (g) + O2 (g)
Keq = PO2 PSO22 = (0.343)(0.00419)2 = 1.34x10-2
PSO32 (0.0212)2

2. KEY
6. A mix of 0.10 mol of NO, 0.050 mol of H2, and 0.10 mol of H2O is placed in a 1.0 L
vessel at 300K. At equilibrium PNO = 0.062, calculate the equilibrium concentrations
of H2, N2 and H2O and Kc.
2NO (g) + 2H2 (g)  N2 (g) + 2H2O (g)
.1 .05 ? .1
NO H2  N2 H2O
I .1 .05 0 1
C .1 - .062 = -0.038 -0.038 (1/2)X X
=X X +0.019 +0.038
E 0.062 .05 - .038 = .012 0.019 0.138
(.1-x) (.05-x) ( 1/2x ) (x)
Kc = [N2][H2O]2 = (0.019)(0.138)2 = (0.02)(0.14)2 = 653.7 = 7x102
[NO]2[H2]2 (0.0620)2(0.012)2 (0.06)2(0.01)2
7. A mixture of 0.2000 mol of CO2, 0.1000 mol of H2 and 0.1600 mol of H2O is
placed in a 2.000 L vessel. The following equilibrium is established at 500K:
CO2(g) + H2(g)  CO(g) + H2O (g)
a) calculate the initial partial pressures of CO2, H2 and H2O.
b) At equilibrium PH2O = 3.51 atm. Calculate the equilibrium partial pressures of
CO2, H2 and CO.
c) Calculate Kp for the reaction.
a) P = nRT/V;
PCO2 = 0.2000 mol x 500K x 0.08206 L atm = 4.103 atm
2L K mol
PH2 = 0.1000 mol x 500K x 0.08206 L atm = 2.0515 atm
2L K mol
PH2O = 0.16000 mol x 500K x 0.08206 L atm = 3.282 atm
2L K mol
b) The change in PH2O is 3.51 – 3.28 = 0.2276 = 0.23 atm. From the reaction
stoichiometry, calculate the change in the other pressures and the equilibrium pressures.
CO2 H2  CO H 2O
I 4.1 atm 2.05 atm 0 atm 3.28 atm
C -0.23 atm -0.23 atm +0.23 atm +0.23 atm
E 3.87 atm 1.82 atm 0.23 atm 3.51 atm
c) Kp = PCO PH2O = (0.23)(3.51) = 0.11
PCO2 PH2 (3.87)(1.82)