Question

A)

Solid nickel(II) nitrate is slowly added to 175 mL of a 0.0527 M potassium cyanide solution. The concentration of nickel ion required to just initiate precipitation is __________ M ?

B)

Solid manganese(II) acetate is slowly added to 150 mL of a 0.0530 M potassium hydroxide solution. The concentration of manganese(II) ion required to just initiate precipitation is ______ M.?

Answer 1

A) concentration of nickel ion = 1.08 x 10^-20 M

B) concentration of manganese ion = 1.64 x 10^-11 M

Explanation

A) K_sp Ni(CN)₂ = 3.0 x 10^-23

Also, K_sp Ni(CN)₂ = [Ni²⁺][CN^-]²

3.0 x 10^-23 = [Ni²⁺][CN^-]²

3.0 x 10^-23 = [Ni²⁺] * (0.0527 M)²

[Ni²⁺] = 3.0 x 10^-23 / (0.0527 M)²

[Ni²⁺] = 1.08 x 10^-20 M