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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3rx220

In iodimetric determinations with $I X_{2}$ as the titrant (I = 127, As = 75, S = 32, C = 12, H = 1, O = 16), which equivalent masses are correct?

A $As X_{2} O X_{3}$ (to arsenate), molar mass 198: equivalent mass 49.5
B $H X_{2} S$ (to S), molar mass 34: equivalent mass 34
CAscorbic acid $C X_{6} H X_{8} O X_{6}$ (to dehydroascorbic acid), molar mass 176: equivalent mass 88
D $Na X_{2} S X_{2} O X_{3} \cdot 5 H X_{2} O$ (to $S X_{4} O X_{6} X^{2 -}$ ), molar mass 248: equivalent mass 248

Answer: A, C, D

As X_{2} O X_{3}

gives 2 As(III) to As(V), 4 electrons: 198/4 = 49.5.

H X_{2} S

(S: -2 to 0) loses 2 electrons: 34/2 = 17, not 34. Ascorbic acid loses 2 electrons: 176/2 = 88. Thiosulphate loses 1 electron per ion: 248. A, C and D are correct.

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