Page No 189: - Chapter 7 P Block Elements Intext Solutions class 12 ncert solutions Chemistry - SaraNextGen [2024-2025]

Updated By SaraNextGen

On April 24, 2024, 11:35 AM

Question 7.20:

What happens when sulphur dioxide is passed through an aqueous solution of Fe(III) salt?

Answer:

SO₂ acts as a reducing agent when passed through an aqueous solution containing Fe(III) salt. It reduces Fe(III) to Fe(II) i.e., ferric ions to ferrous ions.

Question 7.21:

Comment on the nature of two S−O bonds formed in SO₂ molecule. Are the two S−O bonds in this molecule equal?

Answer:

The electronic configuration of S is 1s² 2s² 2p⁶ 3s² 3p⁴.

During the formation of SO₂, one electron from 3p orbital goes to the 3d orbital and S undergoes sp² hybridization. Two of these orbitals form sigma bonds with two oxygen atoms and the third contains a lone pair. p-orbital and d-orbital contain an unpaired electron each. One of these electrons forms pπ- pπ bond with one oxygen atom and the other forms pπ- dπ bond with the other oxygen. This is the reason SO₂ has a bent structure. Also, it is a resonance hybrid of structures I and II.

Both S−O bonds are equal in length (143 pm) and have a multiple bond character.

Question 7.22:

How is the presence of SO₂ detected?

Answer:

SO₂ is a colourless and pungent smelling gas.

It can be detected with the help of potassium permanganate solution. When SO₂ is passed through an acidified potassium permanganate solution, it decolonizes the solution as it reduces