Bleaching powder and bleach solution are produced on a large scale and used in several household products. The effectiveness of bleach solution is often measured by iodometry.
25 mL of household bleach solution was mixed with 30 mL of 0.50 M KI and 10 mL of 4 N acetic acid. In the titration of the liberated iodine, 48 mL of was used to reach the end point. The molarity of the household bleach solution is
25 mL of household bleach solution was mixed with 30 mL of 0.50 M KI and 10 mL of 4 N acetic acid. In the titration of the liberated iodine, 48 mL of was used to reach the end point. The molarity of the household bleach solution is
- (A)0.48 M
- (B)0.96 M
- (C)0.24 M✓ Correct
- (D)0.024 M
Answer: (C)
Solution
The bleach (OCl⁻) oxidizes I⁻ to I₂. The I₂ is then titrated with Na₂S₂O₃. Millimoles of Na₂S₂O₃ = 48 × 0.25 = 12. Since 2 moles of Na₂S₂O₃ react with 1 mole of I₂, millimoles of I₂ = 6. Each mole of OCl⁻ produces 1 mole of I₂, so millimoles of bleach = 6. Molarity = 6/25 = 0.24 M. The answer is (C).
JEE Advanced · 2012 · 08 Apr 2012 · Paper 2 · Single correct option