In the context of radical halogenation of alkanes, chain termination steps are those in which reactive radicals combine to form more stable, non-radical products, thus stopping the chain reaction process. Let's analyze each option:
A) [tex]\( CH_4 + Cl \longrightarrow^{\circ} CH_3+ HCl \)[/tex]
- This is not a chain termination step. This represents a reaction where a methane molecule reacts with a chlorine radical, forming a methyl radical ([tex]\(^{\circ} CH_3 \)[/tex]) and HCl. This is more aligned with a propagation step.
B) [tex]\(^{\prime} CH_3 + Cl_2 \longrightarrow CH_3 Cl + ^{\circ}Cl \)[/tex]
- This is also not a chain termination step. This describes a methyl radical reacting with molecular chlorine to form methyl chloride and a chlorine radical, another propagation step.
C) [tex]\(^{\prime} CH_3 + ^{\prime} CH_3 \longrightarrow CH_3 CH_3 \)[/tex]
- This is a chain termination step. Two methyl radicals combine to form ethane (CH_3CH_3), ceasing the propagation of further radical reactions.
D) [tex]\(^{-} CH _3+ Cl \longrightarrow CH _3 Cl \)[/tex]
- This is not a properly written radical reaction. The correct representation should be considering radicals, but since candidates can clearly see that the radicals combination into stable product is ideal thus properly being a termination step.
Thus, the correct options that indicate chain termination during radical halogenation of alkanes are those where two radicals combine to form a stable product. The correct answer here would be:
C
