JEE Main 2026 — Jan 23, Shift 2 — Chemistry solution

JEE Main2026Jan 23, Shift 2Chemistry

200 cc of $x \times 1 0^{- 3}$ M potassium dichromate is required to oxidise 750 cc of 0.6 M Mohr's salt solution in acidic medium. Here $x =$ ________

Your answer

Solution

In acidic medium, $C r_{2} O_{7}^{2 -}$ is reduced from $C r^{+ 6}$ to $C r^{+ 3}$ (gain of 6 electrons per dichromate), and $F e^{2 +}$ in Mohr's salt is oxidised to $F e^{3 +}$ (loss of 1 electron each).

Equivalents must balance:

$n_{K_{2} C r_{2} O_{7}} \times 6 = n_{F e^{2 +}} \times 1$

$(200 \times x \times 1 0^{- 3}) \times 6 = (750 \times 0.6) \times 1$

(volumes in mL, $\times$ molarity = millimoles)

$1.2 x = 450$

$x = 375$ .

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