Chemistry

Problem

The molar concentration of

\text{SO}_4^{2-}

required to precipitate

\text{RaSO}_4

for

2 \times 10^{-4}

mole of

\text{Ra}^{2+}

in 500 mL is

10^{-a} M

. If

K_{sp}

\text{RaSO}_4

4 \times 10^{-11}

then value of

a

is.....