JEE Main · 2026 · 23 Jan 2026 · Shift 2 · Redox Reactions and Electrochemistry

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 =

Answer: 375

Solution

Mohr's salt supplies Fe

^{2 +}

, oxidised to Fe

^{3 +}

with

n = 1

, while dichromate is reduced,

C r_{2} O_{7}^{2 -} + 14 H^{+} + 6 e^{-} \to 2C r^{3 +} + 7 H_{2} O

, with

n = 6

. Equating milliequivalents,

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

, so

1.2 x = 450

and

x = 375

JEE Main · 2026 · 23 Jan 2026 · Shift 2 · Integer answer