JEE Main2018ChemistryIonic EquilibriumActual
An aqueous solution contains an unknown concentration of Ba 2 + . When 50 mL of a 1 M solution of Na 2 SO 4 is added, BaSO 4 just begins to precipitate. The final volume is 500 mL . The solubility product of BaSO 4 is 1 × 10 - 10 . What is the original concentration of Ba 2 + ?
Options
- A1 .0 × 10 - 10 M
- B5 × 10 - 9 M
- C2 × 10 - 9 M
- D1 .1 × 10 - 9 M
Correct answer
D. 1 .1 × 10 - 9 M
Step-by-step solution
Ba + 2 + SO 4 2 − ⇌ BaSO 4 ( s ) ppt Final conc. of [ SO 4 2 − ] = MV 1 V 1 + V 2 = 1 × 50 500 = 0 .1 M Final conc.of [ Ba + 2 ] When BaSO 4 start precipitating K SP = Q SP = [ Ba + 2 ] [ SO 4 2 − ] 10 − 10 = [ Ba + 2 ] ( 0 .1 M ) Initial conc. [ Ba + 2 ] ; initial volume was = 500 - 50 = 450   ml M 1 V 1 = M 2 V 2 M 1 = M 2 V 2 V 1 = 10 − 9 × 500 450 M 1 = 1 .1 × 10 − 9 M