Question

The Ksp of PbBr, is 6.60 x 10-6. What is the molar solubility of PbBr, in pure water? molar solubility: What is the molar solñbility of PbBr, in 0.500 M KBr solution? molar solubility: What is the molar solubility of PbBr, in a 0.500 M Pb(NO,), solution? molar solubility:

Answer 1

1)

At equilibrium:

PbBr2 <----> Pb2+ + 2 Br-

   s 2s

Ksp = [Pb2+][Br-]^2

6.6*10^-6=(s)*(2s)^2

6.6*10^-6= 4(s)^3

s = 1.182*10^-2 M

Answer: 1.18*10^-2 M

2)

KBr here is Strong electrolyte

It will dissociate completely to give [Br-] = 0.5 M

At equilibrium:

PbBr2 <----> Pb2+ + 2 Br-

   s 0.5 + 2s

Ksp = [Pb2+][Br-]^2

6.6*10^-6=(s)*(0.5+ 2s)^2

Since Ksp is small, s can be ignored as compared to 0.5

Above expression thus becomes:

6.6*10^-6=(s)*(0.5)^2

6.6*10^-6= (s) * 0.25

s = 2.64*10^-5 M

Answer: 2.64*10^-5 M

3)

Pb(NO3)2 here is Strong electrolyte

It will dissociate completely to give [Pb2+] = 0.5 M

At equilibrium:

PbBr2 <----> Pb2+ + 2 Br-

   0.5 +s 2s

Ksp = [Pb2+][Br-]^2

6.6*10^-6=(0.5 + s)*(2s)^2

Since Ksp is small, s can be ignored as compared to 0.5

Above expression thus becomes:

6.6*10^-6=(0.5)*(2s)^2

6.6*10^-6= 0.5 * 4(s)^2

s = 1.817*10^-3 M

Answer: 1.82*10^-3 M