Question

Which is more soluble in water, silver chromate (AgCrO4, [Ksp=2.6*10-^-12], or silver chloride (AgCl, [Ksp=1.8*10^-10])? Justify your answer.

Answer 1

First of all Silver chromate is Ag₂CrO_4, not AgCrO4.

Ksp refers to the dissolution reaction:

Ag2CrO4(s) 2Ag+ (aq) + CrO4 - (aq)

Ksp(Ag2CrO4) = [Ag+ (aq)]2 [CrO4 - (aq)]

Ksp = 4s³

  2.6*10-^-12 = 4s³

s³  = 0.65*10^-12

s = (0.65*10^-12)^1/3

   ⁼ 0.000065 M

= 6.5 X 10^-5  M

Soubility of Silver chromate is 6.5 X 10^-5  M

For AgCl,

AgCl(s) Ag+ (aq) + Cl- (aq)

Ksp(AgCl) = [Ag+ (aq)][Cl- (aq)]

Ksp = s²

1.8*10^-10 = s²

s = (1.8*10^-10)^1/2

   ⁼ 0.000013416 M

= 1.34 X 10^-5 M

Solubility of silver chloride = 1.34 X 10^-5 M

Hence, Silver chromate  is more soluble.