`K_(sp)` for `Cr(OH)_(2)` is `2.7 xx 10^(-13)` . What is its solubility in moles `//` litre ?

Options

A. `1.7 xx 10^(-8)`
B. `2.7 xx 10^(-8)`
C. `1 xx 10^(-8)`
D. `1. 36 xx 10^(-8)`

Answer

C

Explanation

Let solubility of `Cr(OH)_(3)` is s mol `L^(-1)`
`:. [Cr^(3+)]=s mol L^(-1) ` and `[OH^(-)]=3 s mol L^(-1)`
`:. K_(sp)=[Cr^(3+)][OH^(-)]^(3)`
`2.7 xx 10^(-31)=s (3s)^(3)`
`27 s^(4)=2.7 xx 10^(-31)`
`s^(4) =10^(-32)`
`s=1 xx 10^(-8)`