Question

Mg(OH)2 is a sparingly soluble compound, in this case a base, with a solubility product, Ksp, of 5.61×10−11. It is used to control the pH and provide nutrients in the biological (microbial) treatment of municipal wastewater streams. Based on the given value of the Ksp, what is the molar solubility of Mg(OH)2 in pure H2O?

Answer 1

0.000241 M is the molar solubility of
`Mg(OH)_2` in pure water.

Step-by-step explanation:

Solubility product of metal hydroxide =
`K_(sp)=5.61* 10^(-11)`

`M(OH)_2\rightleftharpoons M^(2+)+2OH^-`

S 2S

The expression of a solubility product is given by :

`K_(sp)=[M^(2+)][OH^-]^2`

`K_(sp)=S* (2S)^2=4S^3`

`5.61* 10^(-11)=4S^3`

Solving for S:

`S=0.000241 M`

0.000241 M is the molar solubility of
`Mg(OH)_2` in pure water.