Question
Sun August 28, 2011 By: Piyush Das

Why AgCl dissolves in CH3NH2 solution?

Expert Reply
Wed September 14, 2011

 

Amines containing 1 to 4 carbon atoms are water soluble, and like MH3 they are weak bases. For example,

CH3NH2(aq)     +    H2O(l)         CH3NH3+(aq)     +    OH-(aq)

Methylamine                               Methylammonium

                                                         ion

The solubility product, Ksp, for AgCl is 1.6 x 10?10, now when it reacts with CH3NH2,there is formation of of soluble and stable complex  ,i.e.,[Ag(NH3CH3)2]+, i.e.,

‘2’ reactions involved:- The reaction for the solubility of a saturated solution of sparingly soluble salt ‘AgCl’

AgCl (saturated,sparingly soluble)Ag+(aq) +Cl-(aq)     (1)     , Ksp=[Ag+][Cl-]                        

The stability constant  representing the formation of complex ,[Ag(NH3CH3)2]+,

Ag+(aq) + CH3NH3+(aq)  [Ag(NH3CH3)2]+(aq),                                  (2)

So, Ag+ is getting consumed to form a stable complex i.e.[Ag(NH3CH3)2]+and AgCl gets dissolved in CH3NH2 solution.

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