Solubility product of silver bromide is 5.0x10^-13

• Equilibrium

Solubility product of silver bromide is 5.0x10^-13. The quantity of potassium bromide (molar mass taken as 120 g mol^–1) to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is

1. 6.2 x 10^-5 g
2. 5.0 x 10^-8 g
3. 1.2 x 10^-9 g
4. 1.2 x 10^-10 g

Answer

For precipitation

[Ag⁺][Br^-] > K_sp[AgBr]

[Br^-]_min = (5 x 10^-13)/0.05 = 10^-11 M

Mass of potassium bromide needed = 10^-11 x 120

= 1.2 x 10^-9 g

The correct option is C.