Question

At what minimum value of pH a 0.5 M aqueous solution of metal bromide [MBra] saturated with 01 M H S will cause precipitation of salt MS?​

Answer 1

Answer:

For the precipitation of MS from a solution of MBr2 by passing H2S

KspMS=[M2+][S2−]

or 6×10−21=[0.05][S2−]

or [S2−]=1.2×10−19M

i.e., precipitation of MS will start when H2S provides

1.2×10−19M ion of S2−

For H2S

H2S⇌2H++S2−

$k = k_{1} \times k_{2} = \frac{ {h}^{1} {s}^{2 - } }{ s_{2}s } =$

or 10−7×1.3×10−13=

$\frac{ {h}^{ + }1.2 \times {10}^{ - 19} }{0.1}$

or [H+]=1.04×10−1

∴ pH=0.9826