c C+ d D? e E+ f F K 2=[E] e [F] f [C] c [D] d a A+ b B? e E+ f F K 3=[E] e [F]

Question

cC+dD?eE+fF

K2=[E]e[F]f[C]c[D]d

aA+bB?eE+fF

K3=[E]e[F]f[A]a[B]b=[C]c[D]d[A]a[B]b?[E]e[F]f[C]c[D]d

K3=K1?K2

Thus, when a chemical equation is the sum of two chemical equations for which equilibrium constants are already known, the equilibrium constant for the reaction is the product of the equilibrium constants for the individual reactions. Keep in mind that equilibrium equations do not include expressions for any pure solids or liquids that may be involved in the reaction.

Part A

H2S?HS?+H+,   K1 = 9.64

cC+dD?eE+fF

the equilibrium equation is given by

K2=[E]e[F]f[C]c[D]d

If the first two equations are added together such that

aA+bB?eE+fF

then the equilibrium equation is given by

K3=[E]e[F]f[A]a[B]b=[C]c[D]d[A]a[B]b?[E]e[F]f[C]c[D]d

or

K3=K1?K2

Thus, when a chemical equation is the sum of two chemical equations for which equilibrium constants are already known, the equilibrium constant for the reaction is the product of the equilibrium constants for the individual reactions. Keep in mind that equilibrium equations do not include expressions for any pure solids or liquids that may be involved in the reaction.

Part A

Given the two reactions

H2S?HS?+H+,   K1 = 9.64

Explanation / Answer

H2S ---->HS- + H+ K1=9.64x10^8 K1=[HS-]x[H+] / [H2S]

2HS- ----->S2+ 2H+ K2=1.43x100^19 K2=[S2]x[H]^2 /[HS]^2

S2 +4H+------>2H2S K=? K=[H2S]^2 /[S2]x[H]^4

K=1/K1^2 xK2 =1/92.64 x1.43x10^3=0.01538x10^3

2-PbCl2----->Pb^+2 + 2Cl^ K3=1.8X10 K3=[Pb^+2]x[Cl]^2

2AgCl--------->2Ag^+ +2Cl^- K4^2=(1.13x10^4)^2 ( K4)^2=[Ag]^2x [Cl]^2/[AgCl]^2

PbCl2 + 2Ag^+ ------>2AgCl +Pb^+2 K=[Pb]^2 x[AgCl]^2 /[PbCl2]x[Ag]^2

K=K3 / K4^2 =1.8x10 /1.4428x10^8=1.247574x10^-7

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