Question

An aqueous solution contains an unknown concentration of Ba2+. When 50 mL of a 1 M solution of Na2SO4 is added, BaSO4 just begins to precipitate. The final volume is 500 mL. The solubility product of BaSO4 is 1×10-10. What is the original concentration of Ba2+?

(1) 2 × 10–9M
(2) 1.1 × 10–9 M
(3) 1.0 × 10–10M
(4) 5 × 10–9 M

Answer 1

Correct option(2) 1.1 × 10–9 M

Explanation:

Its given that the final volume is 500 mL and this final volume has arrived when 50 mL of 1 M Na2SO4 was added to unknown Ba2+ solution.

So, we can interpret the volume of unknown Ba2+ solution as 450 mL i.e.