PractifyUs

NEET Chemistry · d- and f-Block Elements

Potassium dichromate and potassium permanganate

Taught in NCERT Class 12 Chemistry, Chapter 4: The d- and f-Block Elements.

3 verified questions: Easy 0 · Medium 2 · NEET level 1

Sample questions

Sample 1Medium

The dichromate ion is drawn as two tetrahedra, each with a chromium atom at its centre and oxygen atoms at its four corners, the two tetrahedra sharing one corner oxygen atom. What are the oxidation state of chromium and the number of Cr–O–Cr linkages in the ion?

  1. A

    +3 and one

  2. B

    +6 and one

  3. C

    +7 and one

  4. D

    +6 and two

Show the answer
The answer is B.

In Cr2O7²⁻, 2x + 7(−2) = −2, so x = +6. The two CrO4 tetrahedra share one corner oxygen, which forms a single Cr–O–Cr linkage.

  • A.

    +3 is the state of chromium after dichromate is reduced, not in the dichromate ion.

  • C.

    +7 is the oxidation state of manganese in permanganate; for Cr2O7²⁻, 2x − 14 = −2 gives x = +6.

  • D.

    The two tetrahedra share only one corner, so there is a single Cr–O–Cr bridge.

NCERT: Class 12 Chemistry, Chapter 4

Sample 2NEET level

Consider the following statements: I. Chromate and dichromate ions are interconvertible in aqueous solution depending on its pH. II. In acidic solution, the permanganate ion is reduced to Mn²⁺, gaining five electrons. III. Both the manganate and the permanganate ions are paramagnetic. IV. In the dichromate ion, two tetrahedra share one corner with a Cr–O–Cr bond. Which of the statements are correct?

  1. A

    I, II and IV only

  2. B

    I and III only

  3. C

    II, III and IV only

  4. D

    I, II, III and IV

Show the answer
The answer is A.

Chromate and dichromate interconvert with pH, and in acid MnO4⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H2O. The green manganate ion is paramagnetic with one unpaired electron but permanganate is diamagnetic, so III is false; dichromate has two tetrahedra sharing one corner (Cr–O–Cr).

  • B.

    Statement III is false, and II and IV are also correct.

  • C.

    Statement III is false: permanganate is diamagnetic, and I is also correct.

  • D.

    Statement III is false: permanganate is diamagnetic.

NCERT: Class 12 Chemistry, Unit 4 (The d- and f-Block Elements), Some Important Compounds of Transition Elements: Potassium dichromate and Potassium permanganate

Practise Potassium dichromate and potassium permanganate

Practice at the level you choose, with the answer after every question; timed tests with the answers when you submit. Every question is verified against NCERT first.

Sign in to practise

More in d- and f-Block Elements