Question

At 25 °c only 0.0470 mol of the generic salt ab3 is soluble in 1.00 l of water. what is the ksp of the salt at 25 °c?

Answer 1

when we have the balanced equation for this reaction:
AB3 ↔ A+3 + 3B-
So we can get Ksp:
when Ksp = [A+3][B-]^3
when [A+3] = 0.047 mol and from the balanced equation when
1 mol [A+3] → 3 mol [B-]
0.047 [A+3] → ??
[B-] = 3*0.047 = 0.141
so by substitution in Ksp formula:
∴Ksp = 0.047 * 0.141^3
= 1.32x10^-4