Question

The solubility product of CuS, Ag₂S and HgS are 10^-31, 10^-44 and 10^-54 respectively. The solubilities of these sulphides are in the order 

(a) HgS > Ag₂S > CuS 

(b) CuS > Ag₂S > HgS 

(c) Ag₂S > CuS > HgS 

(d) AgS > HgS > CuS

Answer 1

The correct option is: (c)  Ag₂S >CuS > HgS 

Explanation:

For CuS &HgS Ksp=S²  (where s= solubility) & for Ag₂S ; Ksp=4S³(s= solubility) now put the values of Ksp and check in which case the value of S is highest & lowest.         

Solubility of CuS :  (10^-31)^1/2 = ( 10^-31/2); 

 Ag₂S :  (10^-44)^1/3 =( 10^-44/3);  

HgS ;  

(10^-54)^1/2 = (10 ^-54/2) =(10^-27);  

The order of solubility will be as per above values:  

Hence ,the order of solubility is:  Ag₂S> CuS > HgS

Comments

But the answer given here is (C)