Question

How is chloroform converted into methane?

Answer 1

We must know that the formula for chloroform is ${\text{CHC}}{{\text{l}}_{\text{3}}}$and methane is ${\text{C}}{{\text{H}}_{\text{4}}}$. Here, reduction is the process undertaken to convert chloroform into methane.

Complete step-by-step answer:
We can convert chloroform into methane by reduction process. Therefore, we can reduce chloroform in the presence of ${\text{Zn/}}{{\text{H}}_{\text{2}}}{\text{O}}$ into methane.
${\text{CHC}}{{\text{l}}_{\text{3}}} + {\text{6[H]}}\xrightarrow{{{\text{Zn/}}{{\text{H}}_{\text{2}}}{\text{O}}}}{\text{C}}{{\text{H}}_{\text{4}}} + {\text{3HCl}}$
Therefore in the reaction, ${\text{Zn/}}{{\text{H}}_{\text{2}}}{\text{O}}$act as a reducing agent. And we get hydrochloric acid as a by-product. We can also prepare methane from chloroform by photochemical reaction.

Additional information:
We must know it is interesting to note that chloroform can be prepared from methane (reserve of the question asked) via substitution reaction in the presence of diffused light.

$$C{H_4} + C{l_2}\xrightarrow{{h\nu }}C{H_3}Cl + HCl \\\ C{H_3}Cl + C{l_2}\xrightarrow{{h\nu }}C{H_2}C{l_2} + HCl \\\ C{H_2}C{l_2} + C{l_2}\xrightarrow{{h\nu }}CHC{l_3} + HCl \\\$$

The product of the above reaction is chloroform. One of the hydrogen atoms in the methane is replaced by a chlorine atom in each step that is why this is called a substitution reaction. However, the reaction doesn't stop there, and until all the hydrogen in the methane is replaced by chlorine atoms into carbon tetrachloride.
$CHC{l_3} + C{l_2}\xrightarrow{{h\nu }}CC{l_4} + HCl$

Note: We must know that methane is hydrocarbon which can be formed by decay of natural materials and primarily used as a fuel. It is known as natural fuel to make heat and light. And it has some physical property such as odourless, colourless, flammable gas. It is also used to manufacture other organic chemicals by different processes.
It is interesting to note that Zinc in the presence of other solvents gives different products with chloroform.

$${\text{CHC}}{{\text{l}}_{\text{3}}} + 2{\text{[H]}}\xrightarrow{{{\text{Zn/HCl}}}}{\text{C}}{{\text{H}}_{\text{2}}}{\text{C}}{{\text{l}}_2} + {\text{HCl}} \\\ {\text{CHC}}{{\text{l}}_{\text{3}}} + 4{\text{[H]}}\xrightarrow{\begin{subarray}{l} {\text{Zn/HCl}} \\\ {\text{in }}{{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{OH}} \end{subarray} }{\text{C}}{{\text{H}}_3}{\text{Cl}} + 2{\text{HCl}} \\\$$

There are other reducing agents like lithium aluminium hydride and metals like nickel reduce the chloroform into methane.
${\text{CHC}}{{\text{l}}_{\text{3}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{/Ni}} \to {\text{C}}{{\text{H}}_{\text{4}}}$
${\text{CHC}}{{\text{l}}_{{\text{3}}}}{\text{ + LiAl}}{{\text{H}}_{\text{4}}} \to {\text{C}}{{\text{H}}_{\text{4}}}$