The polymer formed on heating Novolac with formaldehyde is :

Solution

Chemistry ma’am · 4 steps

Novolac is only half-built Bakelite: more formaldehyde links its chains into a rigid network.

1. Where Novolac comes from. Phenol reacts with formaldehyde to give o- and p-hydroxymethylphenols. These condense with more phenol through -CH₂⁻ bridges, giving Novolac, a linear polymer.
2. Heat with HCHO. Heating Novolac with more formaldehyde adds further -CH₂⁻ bridges between neighbouring chains. The chains get cross-linked into one giant three-dimensional network.
3. Name the product. This hard, infusible cross-linked phenol–formaldehyde resin is Bakelite, a thermosetting polymer. That is why it is used for electrical switches and handles of utensils.
4. So. Heating Novolac with formaldehyde gives Bakelite, option (a).

The idea to keep. Phenol + HCHO gives linear Novolac first. Heat it with more HCHO and the chains cross-link into Bakelite. Linear stage and cross-linked stage, same pair of monomers.

Answer from the NTA final answer key. Solution by PrepWiser.