A solution is analysed for a reductant. 25.0 mL of it needs 20.0 mL of 0.0100 M K2Cr2O7 in acid, assuming a quantitative reaction. Which of the following could be the solution? (Fe^2+ to Fe^3+, Sn^2+ to Sn^4+, SO3^2- to SO4^2-)

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3rx217

A solution is analysed for a reductant. 25.0 mL of it needs 20.0 mL of 0.0100 M $K X_{2} Cr X_{2} O X_{7}$ in acid, assuming a quantitative reaction. Which of the following could be the solution? ( $Fe X^{2 +}$ to $Fe X^{3 +}$ , $Sn X^{2 +}$ to $Sn X^{4 +}$ , $SO X_{3} X^{2 -}$ to $SO X_{4} X^{2 -}$ )

Dichromate supplies

20.0 \times 0.0100 \times 6 = 1.20

meq, so the 25.0 mL sample must be 1.20/25.0 = 0.0480 N.

FeSO X_{4}

has n = 1: 0.0480 M.

SnCl X_{2}

and

Na X_{2} SO X_{3}

have n = 2: 0.0240 M. A 0.0480 M sulphite solution is 0.0960 N, twice too concentrated. A, B and C are correct.