Question
200 cc of x 10^ -3 M potassium dichromate is required to oxidise 750 cc of 0.6 M Mohr's salt solution in acidic medium. Here x= \_\_\_\_.
JEE Main
Chemistry
Redox Reactions
2026
JEE Main 2026 (23 January Shift 2)
JEE Main Chemistry Question (2026) — Solution
Options
- A. A
- B. B
- C. C
- D. D
Answer
A. A
Step-by-step solution
Mohr's salt (FeSO_4 (NH_4)_2SO_4 6H_2O) is a source of Fe^ 2+ ions. The redox reaction with potassium dichromate in acidic medium is: 6Fe^ 2+ + Cr_2O_7^ 2- + 14H^+ 6Fe^ 3+ + 2Cr^ 3+ + 7H_2O. Moles of Fe^ 2+ from Mohr's salt solution: n(Fe^ 2+ ) = 0.6 M 0.750 L = 0.45 mol . From the stoichiometry, 6 moles of Fe^ 2+ require 1 mole of Cr_2O_7^ 2- . Moles of Cr_2O_7^ 2- required: n(Cr_2O_7^ 2- ) = 0.45 6 = 0.075 mol . Molarity of potassium dichromate: M = 0.075 mol 0.200 L = 0.375 M = 375 10^ -3 M . Therefore, x = 375.
Related: Chemistry — Redox Reactions · All PYQ Banks