Question

1. You add 34 g of cobalt (ll) hydroxide to a hot tub (V=2500 L). The Ksp of cobalt (ll) hydroxide is 1.3*10^-15. If the hot tub is filled with water, what is the concentration of the cobalt (ll) in the hot tub when it reaches equilibrium?
2. If the hot tub is filled with a solution containing 5.2*10^-5 NaOH, what is the concentration of the cobalt (ll) in the hot tub when it reaches equilibrium?
   

Answer 1

Reaction:

$$\text{Co(OH)}_2=\text{Co}^{2+}+2\text{OH}^-,$$

the solubility constant is

$$K_{sp}=[\text{Co}^{2+}]^1[\text{OH}^-]^2.$$