Chemistry Q61 – JEE-MAIN 2026

Home Chemistry Periodicity & ElementsQuestion #505

Correct statements from the following are A. Potassium dichromate is an oxidising agent and it oxidises

F e S O_{4}

F e_{2} (S O_{4})_{3}

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

C r 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 -}

126^{\circ}

. Choose the correct answer from the options given below:

Clue 1 of 3: Properties of Chromium Compounds

Recall the oxidizing nature of dichromates, their use as primary standards, and the interconversion between chromate and dichromate ions.

🧠 Full Solution Path

Step 1: Analyze Oxidizing Properties and Primary Standard Criteria✦ Active

Statement A: Potassium dichromate ( $K_{2} C r_{2} O_{7}$ ) is a strong oxidizing agent in acidic medium, oxidizing $F e^{2 +}$ to $F e^{3 +}$ . The reaction is $C r_{2} O_{7}^{2 -} + 14 H^{+} + 6 F e^{2 +} \to 2 C r^{3 +} + 6 F e^{3 +} + 7 H_{2} O$ . This statement is correct.

Statement B: A primary standard must be highly pure, stable, and non-hygroscopic. Sodium dichromate ( $N a_{2} C r_{2} O_{7}$ ) is hygroscopic, meaning it absorbs moisture from the air, which makes it unsuitable as a primary standard. Potassium dichromate ( $K_{2} C r_{2} O_{7}$ ) is non-hygroscopic and is used as a primary standard. This statement is incorrect.

Step 2: Examine Interconversion and Molecular Structure○ Expand

Statement C: Chromate ( $C r O_{4}^{2 -}$ ) and dichromate ( $C r_{2} O_{7}^{2 -}$ $) i o n s a r e i n t e r c o n v e r t i b l e i n a q u e o u s s o l u t i o n, w i t h t h e e q u i l i b r i u m b e i n g p H - d e p e n d e n t . I n a c i d i c c o n d i t i o n s,$ 2CrO_4^{2-} + 2H^+ \rightleftharpoons Cr_2O_7^{2-} + H_2O $. I n b a s i c c o n d i t i o n s,$ Cr_2O_7^{2-} + 2OH^- \rightleftharpoons 2CrO_4^{2-} + H_2O$. This statement is correct.

Statement D: The dichromate ion ( $C r_{2} O_{7}^{2 -}$ $) c o n s i s t s o f t w o$ CrO_4 $t e t r a h e d r a s h a r i n g o n e o x y g e n a t o m . T h e C r - O - C r b o n d a n g l e i n t h e d i c h r o m a t e i o n i s e x p e r i m e n t a l l y f o u n d t o b e a p p r o x i m a t e l y$ 126^\circ$. This statement is correct.

Step 3: Identify the Correct Combination of Statements○ Expand

Based on the analysis, statements A, C, and D are correct. Therefore, the option that includes A, C, and D is the correct answer.

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Chemistry Question 61 – JEE-MAIN 2026

Clue 1 of 3: Properties of Chromium Compounds

🧠 Full Solution Path