Correct statements from the following are A. Potassium dichromate is an oxidising agent and it oxidises FeSO_4 to Fe_2(SO_4)_3 in acidic medium. B. Sodium dichromate can be used as primary standard in volumetric estimation. C. CrO_4^ 2- and Cr_2O_7^ 2- are interconvertible in aqueous solution by varying the pH of the solution. D. Cr-O-Cr bond angle in Cr_2O_7^ 2- is 126^ . Choose the correct answer from the options given below:
B. A, C and D Only
Statement A is correct. Potassium dichromate acts as a strong oxidising agent in acidic medium and oxidises Fe^ 2+ to Fe^ 3+ , converting FeSO_4 to Fe_2(SO_4)_3. Statement B is incorrect. Sodium dichromate is deliquescent (absorbs moisture from the atmosphere), which prevents it from being weighed accurately. Therefore, it cannot be used as a primary standard in volumetric estimation. Potassium dichromate is used instead. Statement C is correct. Chromate (CrO_4^ 2- ) and dichromate (Cr_2O_7^ 2- ) ions are interconvertible in aqueous solution depending on the pH of the solution. In acidic medium, chromate changes to dichromate, and in basic medium, dichromate changes to chromate: 2CrO_4^ 2- + 2H^+ Cr_2O_7^ 2- + H_2O. Statement D is correct. The structure of the dichromate ion consists of two tetrahedral CrO_3 groups joined by a bridging oxygen atom, and the Cr-O-Cr bond angle is 126^ . Therefore, statements A, C, and D are correct. Answer: A, C and D Only
Related: Chemistry — d and f Block Elements · All PYQ Banks