Barium sulfate (BaSO₄) is a slightly soluble salt, with K_sp = 1.1 × 10^-10. What mass of Ba²⁺ ions will be present in 1.0 L of a saturated solution of barium sulfate?

Question

Quizplus · Accepted Answer

Using the solubility product expression:
KS1U1B1spS1U1B0 = [Ba2+S1U1P][(SO4)2-S1U1P]
1.1 × 10S1U1P1-10S1S1P0 = x2(1 - 2x)
where x is the molar solubility of BaSO4.
Solving for x gives:
x = 1.4 × 10S1U1P4S1S1P0 M
So the concentration of Ba2+ ions is also 1.4 × 10S1U1P4S1S1P0 M.
Therefore, the mass of BaS1U1P12+S1S1P0 ions present in 1.0 L of solution is:
(1.4 × 10S1U1P4S1S1P0 M)(1.0 L)(2 mol BaS1U1P12+S1S1P0/mol) = 2.8 × 10S1U1P4S1S1P0 g
However, we need to take into account the slight solubility of BaSO4, which means that the actual mass of BaS1U1P12+S1S1P0 ions present will be less than this. The correct answer is therefore A) < 10S1U1P1-7S1S1P0 g, which is the only choice less than 2.8 × 10S1U1P4S1S1P0 g. 
The closest choice to this is C) 0.0014 g, which is the correct answer considering significant figures.

Barium Sulfate (BaSO4) Is a Slightly Soluble Salt, with Ksp

Barium Sulfate (BaSO₄) Is a Slightly Soluble Salt, with K_sp