Question

A.) Solid lead acetate is slowly added to 50.0 mL of a 0.0624 M sodium chromate solution. The concentration of lead ion required to just initiate precipitation is __M

B.) Solid potassium hydroxide is slowly added to 50.0 mL of a 0.0636 M nickel(II) acetate solution. The concentration of hydroxide ion required to just initiate precipitation is __M

Answer 1

A)

Ksp of PbCrO4 = 1.8 x 10^-14

PbCrO4 (s)   -------------> Pb2+ (aq) +   CrO42- (aq)

Ksp = [Pb2+] [CrO42-]

1.8 x 10^-14 = [Pb2+] (0.0624)

[Pb2+] = 2.88 x 10^-13

concentration of lead ion = 2.88 x 10^-13 M

B)

Ksp of Ni(OH)2 = 2.8 x 10^-16

Ni(OH)2 (s)   ---------------> Ni2+ (aq) + 2 OH- (aq)

Ksp = [Ni2+][OH-]^2

2.8 x 10^-16 = 0.0636 x [OH-]^2

[OH-] = 6.64 x 10^-8 M