Part A Given the two reactions H2SHS+H+, K 1 = 9.65×10 8 , and HSS2+H+, K 2 = 1.
ID: 531644 • Letter: P
Question
Part A
Given the two reactions
H2SHS+H+, K1 = 9.65×108, and
HSS2+H+, K2 = 1.40×1019,
what is the equilibrium constant Kfinal for the following reaction?
S2+2H+H2S
Enter your answer numerically.
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Part B
Given the two reactions
PbCl2Pb2++2Cl, K3 = 1.78×1010, and
AgClAg++Cl, K4 = 1.14×104,
what is the equilibrium constant Kfinal for the following reaction?
PbCl2+2Ag+2AgCl+Pb2+
Express your answer numerically.
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Kfinal =Explanation / Answer
Part A
The given reactions are:
H2S <=====> H+ + HS-; K1 = 9.65*10-8 …..(1)
HS- <=====> H+ + S2-; K2 = 1.40*10-19 …..(2)
The required reaction is
S2- + 2 H+ <=====> H2S ….(3)
Expression (3) obtained by reversing (2) and (1) and adding the reverse equations. The reverse equations are below:
H+ + HS- <=====> H2S; K1’ = 1/K1 = 1/(9.65*10-8) = 1.036*107
S2- + H+ <======> HS-; K2’ = 1/K2 = 1/(1.40*10-19) = 7.143*1018
The overall equilibrium constant is
K = [H2S]/[S2-][H+]2 = {[H2S]/[H+][HS-]}*{[HS-]/[S2-][H+]} = K1’*K2’ = (1.036*107)*(7.143*1018) = 7.400*1025 7.4*1025 (ans)