What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01 M Z n C l2 and saturated with 0.10 M H2S ? [Given Ks p=10- 21, Ka1 × Ka2=10- 20 ]

Question

What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01 M Z n C l2 and saturated with 0.10 M H2S ? [Given Ks p=10- 21, Ka1 × Ka2=10- 20 ] (A) 0 (B) 1 (C) 2 (D) 4

Tardigrade Admin · Accepted Answer

K sp for ZnS =[ Zn 2+][ S 2-] [ S 2-]=(10-21/0.01)=10-19 H 2 S leftharpoons H ++ HS - K a 1=( H + HS -/ H 2 S ) HS - leftharpoons H ++ S 2- K a 2=( H + S 2-/ HS -) for K a 1 ⋅ K a 2=([ H +]2[ s 2-]/[ H 2 s ]) 10-20=([ H +]2 × 10-19/0.1) ⇒[ H +]=0.1 or pH =1

Q. What is the minimum $p H$ required to prevent the precipitation of $Z n S$ in a solution that is $0.01 M Z n C l_{2}$ and saturated with $0.10 M H_{2} S$ ?
[Given $K_{s p} = 1 0^{- 21}, K_{a_{1}} \times K_{a_{2}} = 1 0^{- 20}$ ]

$0$

$1$

$2$

$4$

Q. What is the minimum pH required to prevent the precipitation of ZnS in a solution that is 0.01MZnCl2​ and saturated with 0.10MH2​S ? [Given Ksp​=10−21,Ka1​​×Ka2​​=10−20 ]

0

1

2

4

Ksp​ for ZnS=[Zn2+][S2−] [S2−]=0.0110−21​=10−19 H2​S⇌H++HS−Ka1​​=H2​SH+HS−​HS− ⇌H++S2−Ka2​​=HS−H+S2−​ for Ka1​​⋅Ka2​​=[H2​s][H+]2[s2−]​ 10−20=0.1[H+]2×10−19​⇒[H+]=0.1 or pH=1

Q. What is the minimum $p H$ required to prevent the precipitation of $Z n S$ in a solution that is $0.01 M Z n C l_{2}$ and saturated with $0.10 M H_{2} S$ ?
[Given $K_{s p} = 1 0^{- 21}, K_{a_{1}} \times K_{a_{2}} = 1 0^{- 20}$ ]

$0$

$1$

$2$

$4$