At a certain temperature, the solubility of strontium arsenate, sr3 (aso4) 2, is 0.0590 g/l. what is the ksp of this salt at this temperature?

First, we have to change Sr3 (ASO4) 2 from 0.059 g/L to moles:

and when the molar mass of Sr3 (ASO4) 2 = 87.6*3 + 74.9*2 + 16*8

= 540.6 g/mol

Molarity (X) = 0.059 g/L * 1 mol / 540.6 g/mol

= 1.1 x 10^-4 moles

When the solubility equation is:

Sr3 (ASO4) 2 ↔ 3Sr + + (aq) + 2ASO-3 (aq)

so, Ksp = [Sr++]^3[ASO-3]^2

from ICE table and the balanced equation:

[Sr++] = 3 X

= 3 * 1.1 x 10^-4 = 3.3x10^-4 M

[ASO-3] = 2X

= 2 * 1.1 x 10^-4 = 2.2 x 10^-4 M

So, by substitution:

∴Ksp = (3.3 x 10^-4) ^3 * (2.2 x 10^-4) ^2

= 1.74 x 10^-18