JEE Main 2026 — Apr 4, Shift 1 — Chemistry solution

JEE Main2026Apr 4, Shift 1Chemistry

Correct statements from the following are

A. Potassium dichromate is an oxidising agent and it oxidises $FeS O_{4}$ to $F e_{2} (S O_{4})_{3}$ in acidic medium.

B. Sodium dichromate can be used as primary standard in volumetric estimation.

C. $Cr O_{4}^{2 -}$ and $C r_{2} O_{7}^{2 -}$ are interconvertible in aqueous solution by varying the pH of the solution.

D. Cr $-$ O $-$ Cr bond angle in $C r_{2} O_{7}^{2 -}$ is $12 6^{\circ}$ .

Choose the correct answer from the options given below :

A
A, B and C only
B
A, C and D only
C
A and C only
D
B and D only

Solution

A. $K_{2} C r_{2} O_{7}$ in acidic medium oxidises Fe $^{+ 2}$ to Fe $^{+ 3}$ , converting $FeS O_{4}$ to $F e_{2} (S O_{4})_{3}$ . Correct.

B. $N a_{2} C r_{2} O_{7}$ is deliquescent (absorbs moisture from air), so it cannot be weighed accurately and is not used as a primary standard. $K_{2} C r_{2} O_{7}$ is the one used as a primary standard. Incorrect.

C. The equilibria $2 Cr O_{4}^{2 -} + 2 H^{+} ⇌ C r_{2} O_{7}^{2 -} + H_{2} O$ and $C r_{2} O_{7}^{2 -} + 2 O H^{-} ⇌ 2 Cr O_{4}^{2 -} + H_{2} O$ confirm pH-driven interconversion. Correct.

D. The bridging Cr $-$ O $-$ Cr angle in dichromate is indeed about $12 6^{\circ}$ . Correct.

Hence A, C and D.

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