In: Chemistry
Part A. Given the two reactions:
H2S⇌HS−+H+, K1 = 9.52×10−8,
HS−⇌S2−+H+, K2 = 1.18×10−19, what is the equilibrium constant Kfinal for the following reaction? S2−+2H+⇌H2S
Enter your answer numerically.
Part B. Given the two reactions:
PbCl2⇌Pb2++2Cl−, K3 = 1.87×10−10
AgCl⇌Ag++Cl−, K4 = 1.22×10−4
what is the equilibrium constant Kfinal for the following reaction? PbCl2+2Ag+⇌2AgCl+Pb2+
Express your answer numerically.
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Part - A: The given equilibrium reactions are
H2S <-----> HS- + H+ ; K1 = 9.52x10-8 -------(1)
HS- <-----> S2- + H+ ; K2 = 1.18x10-19 ------(2)
Adding equation(1) and (2) we get
H2S <-----> S2- + 2H+ ; K' = K1xK2 = 9.52x10-8x1.18x10-19 = 1.12336x10-26 ----- (3)
Now reversing the equation(3) we will get the desired equation.
S2- + 2H+ ------ > H2S, K'' = 1 / K' = 1 / 1.12336x10-26 = 8.90x1025 (answer)
Part - B: The given equilibrium reactions are
PbCl2 <-----> Pb2+ + 2Cl- ; K3 = 1.87x10-10 -------(4)
AgCl <-----> Ag+ + Cl- ; K4 = 1.22x10-4 ------(5)
Adding equation(5) by 2 and then reversing the multiplied equation we get
2Ag+ + 2Cl- <-----> 2AgCl ; K' = 1 / (1.22x10-4 )2 = 6.72x107 ----- (6)
Now we will get the desired equation by adding equation (4) and equation (6)
PbCl2 + 2Ag+ + 2Cl- <------> Pb2+ + 2Cl- + 2AgCl
or PbCl2 + 2Ag+ <------> Pb2+ + 2AgCl; K" = K3 x K' = 1.87x10-10 x 6.72x107 = 1.26x10-2 (answer)