Question

During oxidation of ferrous sulphate using mixture of dil.H2SO4 and potassium dichromate; oxidation state of chromium changes from____. a)+6 to +2. b)+6 to +3. c)+6 to +1. d) +6 to +4

Answer 1

Answer:

b)

Explanation:

Potassium has oxidation state of 6 at the initial state which changes to 3 ... Check out for a video for calculating oxidation state on youtube and then refer me.!

Answer 2

The oxidation state of chromium changes from

b)+6 to +3.

The reaction which occurs between ferrous sulphate (FeSO₄) with potassium dichromate (K₂Cr₂O₇) and H₂SO₄ is shown below.

K₂Cr₂O₇ + 6FeSO₄ + 7H₂SO₄ → Cr₂(SO₄)₃ + 3Fe₂(SO₄)₃ + K₂SO₄ + 7H₂O

Here, K₂Cr₂O₇ changes to Cr₂(SO₄)₃ at the end of the reaction.

The oxidation no. of K is +1 and for O it is -2 and for the SO₄ entity it is -2.

Let the oxidation no. of Cr in K₂Cr₂O₇ be x.

So, 2 + 2x + 7(-2) = 0

⇒ 2x - 14 + 2 = 0

⇒ 2x = 12

⇒ x = 12/2 = +6

Let the oxidation no. of Cr in Cr₂(SO₄)₃ be y.

So, 2y + 3(-2) = 0

⇒ 2y - 6  = 0

⇒ 2y = 6

⇒ y = 6/2 = +3

So, option (b) is correct.