Transition and InnerTransition Elements - Result Question 142

####42. The correct statement(s) about Cr2+ and Mn3+ is/are [atomic number of Cr=24 and Mn=25 ]

(2015 Adv.)

(a) Cr2+ is a reducing agent

(b) Mn3+ is an oxidising agent

(c) both Cr2+ and Mn3+ exhibit d4 electronic configuration

(d) when Cr2+ is used as a reducing agent, the chromium ion attains d5 electronic configuration

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Answer:

Correct Answer: 42. (a,b,c)

Solution:

  1. In aqueous solution Cr2+(3d4) acts as a reducing agent, oxidising itself to Cr3+(3d3) that gives a completely half-field t2g level in octahedral ligand field of H2O.

(b) Mn3+(3d4) is an oxidising agent as it is reduced to Mn2+(3d5), a completely half-filled stable configuration.

(c) Both Cr2+ and Mn3+ have d4 configuration.

(d) 3d4Cr2+(aq) R.A Cr3+(aq)+e

Hence (d) is wrong statement.



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