30.0 mL of 0.0250 M iodine solution is titrated with 0.100 M Na2S2O3. The volume of thiosulfate needed is:

JEE Main levelSingle correct optionDifficulty 2 of 3eq138

30.0 mL of 0.0250 M iodine solution is titrated with 0.100 M $Na X_{2} S X_{2} O X_{3}$ . The volume of thiosulfate needed is:

I X_{2} + 2 S X_{2} O X_{3} X^{2 -} 2 I X^{-} + S X_{4} O X_{6} X^{2 -}

, so 1 mol

I X_{2}

needs 2 mol thiosulfate.

I X_{2}

= 0.0250

\times

30.0 = 0.750 mmol, thiosulfate = 1.50 mmol, volume = 1.50/0.100 = 15.0 mL.