In a chain mechanism, a reaction in which two free radicals combine to form a stable molecule would be called the
A) initiation step
B) termination step
C) propagation step
D) inhibition step
E) branching step
To determine the answer, let's break down the given options and understand each one of them. In a chain mechanism, three main steps occur: initiation, propagation, and termination. Let's analyze each option to identify which step describes the reaction where two free radicals combine to form a stable molecule.
A) Initiation step: This step involves the formation of free radicals from stable molecules. It does not describe the reaction where two free radicals combine to form a stable molecule.
B) Termination step: This step occurs when two free radicals combine, effectively terminating the chain reaction. However, this option describes the opposite of what we are looking for, as it represents the end of the chain reaction rather than the combination of two free radicals to form a stable molecule.
C) Propagation step: This step describes the process in which free radicals are generated and react with stable molecules, creating more free radicals. It does not represent the reaction where two free radicals combine to form a stable molecule.
D) Inhibition step: This step refers to the process by which a substance prevents or slows down a chemical reaction, typically by reacting with a radical. It is not related to the combination of two free radicals to form a stable molecule.
E) Branching step: This step occurs when a radical reacts with a stable molecule, leading to the formation of additional radicals. It does not describe the reaction where two free radicals combine to form a stable molecule.
Based on this analysis, the correct answer is C) propagation step.