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MCQEasyJEE 2023Oxidation States & Ionisation Energies

JEE Chemistry 2023 Question with Solution

The set of correct statements is: (i) Manganese exhibits +7+7 oxidation state in its oxide. (ii) Ruthenium and Osmium exhibit +8+8 oxidation in their oxides. (iii) Sc shows +4+4 oxidation state which is oxidizing in nature. (iv) Cr shows oxidising nature in +6+6 oxidation state.

  • A

    (i) and (iii)

  • B

    (i), (ii) and (iv)

  • C

    (i) and (iii)

  • D

    (ii), (iii) and (iv)

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: Four statements about oxidation states and oxidizing nature of d-block elements are to be checked.

Find: The correct set of statements.

From the provided explanation:

  • Statement (i) is correct because manganese shows +7+7 oxidation state in Mn2O7\text{Mn}_2\text{O}_7.
  • Statement (ii) is correct because ruthenium and osmium show +8+8 oxidation state in RuO4\text{RuO}_4 and OsO4\text{OsO}_4 respectively.
  • Statement (iii) is incorrect because scandium does not show +4+4 oxidation state; it generally shows +3+3 oxidation state.
  • Statement (iv) is correct because chromium in +6+6 oxidation state, such as CrO3\text{CrO}_3, is strongly oxidizing.

Therefore, the correct set of statements is (i), (ii) and (iv), so the correct option is B.

Common mistakes

  • Assuming Sc can commonly show +4+4 oxidation state is incorrect. Scandium predominantly shows +3+3 oxidation state, so statement (iii) must be rejected.

  • Confusing high oxidation state with stability in all elements is wrong. Some elements like Cr in +6+6 state are strongly oxidizing, so statement (iv) is correct.

  • Ignoring well-known oxides such as Mn2O7\text{Mn}_2\text{O}_7, RuO4\text{RuO}_4, and OsO4\text{OsO}_4 can lead to eliminating true statements. Use these standard oxides to verify oxidation states.

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