ANS:A - catalyst supply is stopped.

The statement "Termination of polymerisation reaction occurs if the catalyst supply is stopped" is incorrect. Explanation: In polymerization processes, the catalyst initiates the reaction by facilitating the formation of active species (such as radicals or ions) from the monomer molecules. These active species then react with other monomer molecules to form polymer chains. However, the presence or absence of the catalyst does not directly determine the termination of the polymerization reaction. Here's why:

1. Role of Catalyst: The catalyst's primary role is to initiate the polymerization reaction by breaking chemical bonds in the monomer molecules, thereby generating reactive species capable of initiating chain growth. The catalyst is not directly involved in controlling the termination of the reaction.
2. Termination Mechanisms: Polymerization reactions can terminate through various mechanisms, such as:
   • Exhaustion of monomer supply: Once all the monomer molecules have been consumed, the polymerization reaction naturally ceases.
   • Deactivation of catalyst: Catalysts can become inactive over time due to factors such as degradation, contamination, or depletion of active sites. However, the deactivation of the catalyst does not necessarily terminate the polymerization reaction if sufficient active species are still present to continue chain growth.
   • Chain transfer reactions: During polymerization, growing polymer chains may transfer to other molecules (e.g., solvent molecules or monomer molecules) instead of continuing to grow. This can result in the termination of the polymerization process or the formation of shorter polymer chains.
3. Continuous vs. Batch Processes: In continuous polymerization processes, the catalyst is typically supplied continuously to maintain the reaction. However, the termination of the reaction is not determined solely by the presence or absence of the catalyst. In batch processes, the catalyst may be added initially, but the termination of the reaction is still governed by other factors such as monomer depletion or chain transfer reactions.

Therefore, while the catalyst is essential for initiating the polymerization reaction, its absence or cessation of supply does not directly lead to the termination of the reaction. Termination typically occurs due to other factors such as monomer exhaustion, catalyst deactivation, or chain transfer reactions.