Question

Calculate pH at which `Mg(OH)_(2)` begins to precipitate from a solution containing `0.10M Mg^(2+)` ions. `(K_(SP)of Mg(OH)_(2)=1xx10^(-11))`
A. 4
B. 6
C. 9
D. 7

Answer 1

Correct Answer - C
`K_(sp)" for "Mg(OH)_(2)=1.0xx10^(-11)`
`[Mg^(2+)][OH^(-)]^(2)=(0.1)xx10[OH^(-)]^(2)=1.0xx10^(-11)`
`[OH^(-)]^(2)=(1xx10^(-11))/(0.1)=10^(-10)`
`[OH^(-)]=10^(-5),[H^(+)]=(10^(-14))/(10^(-5))=10^(-9)`
`pH=9`