What type of reaction is polymerisation?

• A. Condensation reaction
• B. Addition reaction
• C. Redox reaction
• D. Dehydration reaction

Answer: (B)

Polymerisation, in this context, is about joining many small molecules into a long chain without losing a small molecule with each bond formed. That describes addition polymerisation, where repeated opening of a double bond (like in alkenes) leads to a growing polymer chain and no byproduct is released.

If polymerisation were a condensation reaction, there would be a small molecule (often water) produced with each linkage. Dehydration is a kind of condensation, but it’s not the general description of polymerisation. Redox involves electron transfer and isn’t the characteristic mechanism for forming polymers.

So the best answer is addition reaction.