Question

Silver chloride is only slightly soluble in pure water at 25∘C:AgCl(s)⇌Ag+(aq)+Cl−(aq)K=1.8×10−10Calculate the concentration of Ag+ and Cl−in a solution that is saturated with AgCl (i.e., the system is at equilibrium and there is still solid AgCl visible).

Answer 1

Ans . For the reaction at 25C AgCl(s)⇌Ag+(aq)+Cl−(aq) ,there exists an equilibrium between the undissolved solid and ions i.e.( Ag+(aq) and Cl- (aq) ) in solution. The equilibrium expression can be written:

K_c = ( [Ag⁺] [Cl¯] ) / [AgCl]

The solid AgCl term in the denominator is actually constant being in the solid state and thus the expression can be written as :

K_c [AgCl] = [Ag⁺] [Cl¯]

Since K_c [AgCl] is a constant , the modified expression becomes K_sp = [Ag⁺] [Cl¯]

Given : K_sp = 1.8 * 10^-10  = s² .

s = (1.8 * 10^-10)^0.5 = 1.341 * 10^-5 M.

Thus the concentration of Ag⁺ and Cl^- = 1.341 * 10^-5 M at equilibrium conditions.