Question

Which of the following not only decolourises alkaline potassium permanganate but also gives red precipitate with ammoniacal cuprous chloride solution ?

• A. Ethane
• B. Methane
• C. Ethene
• D. Acetylene

Answer 1

The correct option is D Acetylene

$CH$$\equiv$$CH$+ $C{u}_{2}C{l}_2$ + $N{H}_{4}OH$ $\to$ + $Cu-C$$\equiv$$C-Cu$ + $N{H}_{4}Cl$ + $2H_{2}O$

$C_2{H}_2$ acetylene is an alkyne and thus forms precipitate with ammonical cuprous chloride solution. Also alkynes decolourises alkaline potassium permanganate solution.

The right option is D