What is the molar solubility of `MgF_(2)` in a 0.2 M solution of KF? `(K_(sp)=8xx10^(-8))`

Options

A. `8xx10^(-8)M`
B. `8xx10^(-7)M`
C. `2xx10^(-6)M`
D. `2.7xx10^(-4)M`

Answer

C

Explanation

`Ksp=[Mg^(+2)][F]^(2)`
`Ksp=(5^('))(25^(')+c)^(2)`
`8xx10^(-8)=5^(')c^(2)`
`s^(')=(8xx10^(-8))/(4xx10^(-2))`
`=2xx10^(-6) M`