Silver chromate is sparingly soluble in aqueous solutions. The 𝐾sp of Ag2CrO4 is 1.12×10−12 .

Question

What is the solubility (in mol/L) of silver chromate in pure water?

Answer 1

The solubility of Ag₂CrO₄ looks like this:

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

Ksp = [Ag⁺]²[CrO₄^2-]

We ignore Ag₂CrO₄ (s) because it is a solid and solids do not appear in our equilibrium constant (where Ksp is the equilibrium constant of solubility).

If we set up an ICE table to find our equilibrium concentrations of our ions:

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

I -- 0 0

C -- +2x +x

E --- 2x x

We start with no product because it is asking how much product is present after the solid dissolves and we ignore the solid all together.

So

Ksp = [Ag⁺]²[CrO₄^2-]

we plug in our "E" values

Ksp = [2x]²[x] = 1.12x10^-12

4x³=1.12x10^-12

when we solve for x, we get x = 0.0000654.

x represents our molar solubility... this is how much our solid dissolves in mol/L so our answer is 0.0000654 mol/L