Question

Explain the term chain reaction with a suitable example

Answer 1

HOPE IT HELP U


The reaction H2 + Br2 → 2 HBr proceeds by the following mechanism:

Initiation

Br2 → 2 Br• (thermal) or Br2 + hν → 2 Br• (photochemical)each Br atom is a free radical, indicated by the symbol « • » representing an unpaired electron.

Propagation (here a cycle of two steps)

Br• + H2 → HBr + H•H• + Br2 → HBr + Br•the sum of these two steps corresponds to the overall reaction H2 + Br2 → 2 HBr, with catalysis by Br• which participates in the first step and is regenerated in the second step.

Retardation (inhibition)

H• + HBr → H2 + Br•this step is specific to this example, and corresponds to the first propagation step in reverse.

Termination 2 Br• → Br2

recombination of two radicals, corresponding in this example to initiation in reverse.