The Equilibrium Constant 1. Given the reaction at equilibrium 2A + B C + 3D, calculate the value of K if the equilibrium concentrations are found to be [A] = 10 M, [B] = 15 M, [C] = 5 M and [D] = 25 M. (Ans: 52) 2. At 773°C a mixture of CO(g), H2(g) and CH3OH(g) was allowed to come to equilibrium. The following equilibrium concentration were then measured [CO] = 0.105 M, [H2] = 0.250 M, [CH3OH] = 0.00261 M. Calculate Keq for the reaction CO(g) + 2H2(g) CH3OH(g) (Ans: 0.398) 3. In the reaction Fe+2(aq) + Ag+(aq) Fe+3(aq) + Ag(s) at equilibrium the following concentrations were found: [Fe+2] = 0.50 M, [Ag+1] = 1.0 M; [Fe+3] = 1.50 M. (a) Calculate the equilibrium constant for the reaction. (b) If at equilibrium [Fe+2] is found to e 0.20 M and [Ag+] is 0.30 M, what must be the concentration of Fe+3? (Ans: a) 3.0 b) 0.18 M) 4. A substance (CD) decomposes into C and D. CD (g) C (g) + D (g). At equilibrium the concentration of CD is 0.17 mol/L. (a) If the initial concentration of CD is 0.2 mol/L, what are the equilibrium concentrations of C and D? (Ans: 0.03, 0.03) (b) What is the K for the reaction at this temperature? (Ans: 5.3x10-3) 5. Fluorine gas F2 reacts with hydrogen gas H2 according to the equation F2(g) + H2(g) 2HF(g) 0.50 mol of each F2 and H2 are placed in a 1.0L vessel and allowed to reach equilibrium at a given temperature. The equilibrium concentration of HF is found to be 0.025 mol/L. What is the value of the equilibrium constant, k for the reaction? (Ans: 2.63x10 -3) 6. When 0.60 mol of gas X and 0.40 mol of gas Y react in a 2.0 L container to produce Z, equilibrium is reached in which [Z] is found to be 0.080 mol/L. The reaction is X(g) + 2Y(g) 2Z(g). Calculate the value of Keq. (Ans: 1.71) 7. Given the equilibrium reaction A(g) + B(g) C(g) when 1.00 mole of both A and B are placed in a 4.0L container, the equilibrium constant is 2.5x10-5. What is the equilibrium concentration of C? (Ans: 1.6x10-6 mol/L) 8. Two moles of NO2(g) are injected into an evacuated 1.0 L flask. The equilibrium constant is 1.23 for 2 NO2(g) N2O4(g). What are the equilibrium concentration of NO2 and N2O4? (Ans: 0.72M, 0.64M) 9. A reaction may be represented by A2(g) + B2(g) 2AB (g). At a given temperature 1.0 mol of A and 1.0 mol of B are placed in the 2.0 L vessel. The K value for this reaction is 3.0x10 -2. What are the equilibrium concentrations of each of the substances? (Ans: 0.46, 0.46, 0.080) 10. For the reaction 2 NH3 (g) N2 (g) + 3 H2 (g) the K value is 16.6. At equilibrium the concentration of H2 is 0.36 mol/L. What was the initial concentration of ammonia? (Ans: 0.26)