Question

question. Solid magnesium hydroxide and solid cobalt(II) hydroxide are in equilibrium with a solution containing 1.18x10-2 M magnesium nitrate. Calculate the concentration of cobalt(II) ion present in this solution. [cobalt(II)] = M

could you please use the ksp values from this list

Answer 1

Mg2+] = [Mg(NO3)2) = 1.18 x 10-2 M

For magnesium hydroxide

Mg(OH)

Ksp = [Mg2+1 x fo - = 1.5 x 10-11

Substitute in above expression

+zw

1.18 x 10-4 x [OH-= 1.5 x 10-11

1.5 x 10-11 OH] = 1.18 x 10-2

JOH-] = 1.27 x 10-

OH-] = V1.27 x 10-9

[OH-] = 3.56 x 10-5 M

For cobalt hydroxide

COOH)2

Ks = [Co2+] * [OH-]2 = 2.5 x 10-16

Substitute in above expression

ОН-

Co2+1 x (3.56 x 10-5)2 = 2.5 x 10-16

Co2+1 x 1.27 x 10-9 = 2.5 x 10-16

2.5 x 10-16 C02+= 1.27 x 10-9

Co2+1 = 1.97 x 10-7 M