JEE MainChemistryRedox Reactions
A 10.0 mL sample of an aqueous H ₂ O ₂ solution is treated with an excess of KI in an acidic medium. The liberated iodine requires 50.0 mL of 0.5 M Na ₂ S ₂ O ₃ solution for complete titration. The volume strength of the H ₂ O ₂ solution is ____. (Given: Molar volume of an ideal gas at STP is 22.4 L )
Correct answer
14
Step-by-step solution
The reactions involved are: H ₂ O ₂ + 2 I ^- + 2 H ^+ I ₂ + 2 H ₂ O I ₂ + 2 Na ₂ S ₂ O ₃ 2 NaI + Na ₂ S ₄ O ₆ From the principle of equivalence: Milliequivalents of H ₂ O ₂ = Milliequivalents of Na ₂ S ₂ O ₃ The n-factor for Na ₂ S ₂ O ₃ is 1 . Milliequivalents of Na ₂ S ₂ O ₃ = 50.0 0.5 1 = 25 Therefore, milliequivalents of H ₂ O ₂ = 25 Let N be the normality of the H ₂ O ₂ solution. N 10.0 = 25 N = 2.5 N The volume strength of H ₂ O ₂ is related to its normality by the formula: Volume strength = 5.6 N (This is de