Question

Part A

Given the two reactions

H2S⇌HS−+H+,   K1 = 9.02×10⁻⁸, and

HS−⇌S2−+H+,   K2 = 1.47×10⁻¹⁹,

what is the equilibrium constant Kfinal for the following reaction?

S2−+2H+⇌H2S

Enter your answer numerically.

Hints

Kfinal=

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Part B

Given the two reactions

PbCl2⇌Pb2++2Cl−,   K3 = 1.81×10⁻¹⁰, and

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.

Hints

Answer 1

part A
adding the two given reaction
we get,
H2S < -- > 2H+ + S2-
when we add equlibrium constant of final reaction is product of equlibrium constant of given
K5 = k1*k2
= 9.02*10^-8*1.47*10^-19
= 1.33*10^-26

so, equlibrium constant of S2−+2H+⇌H2S which is reverse of above reaction
= 1/K5
= 1/(1.33*10^-26)
= 7.52*10^25

Answer : 7.52*10^25
part B
multiply AgCl⇌Ag++Cl− by 2 we get
2AgCl⇌2Ag++2Cl−
equlibrium constant of these reaction will be square of K4
K6 = (1.22*10^-4)^2
= 1.49*10^-8
now add third reaction and the reaction we got by multiplying by 2
we will get the required one of equlibrium constant K7
k7 = K6*K3
= 1.49*10^-8*1.81×10−10
= 2.70*10^-18

Answer : 2.70*10^-18