Question

To distinguish between ethene and ethyne, we should use:

• A. bromine water
• B. potassium permanganate solution
• C. all of the above
• D. ammonical cuprous chloride

Answer 1

Answer: (D)

The two hydrocarbons can be easily distinguished by simple chemical tests, as ethyne molecule is supposed to have acidic hydrogen.

1. When ethyne is bubbled through ammoniacal silver nitrate solution, a yellow-white precipitate of silver acetylide would be formed.

$C_2{H}_2$ + $2AgN{O}_3$ = $A{g}_2{C}_2$ + $2HN{O}_3$

2. Similarly, ethyne forms a red precipitate of copper acetylide ($C{u}_2{C}_2$) when it is passed through ammoniacal cuprous chloride solution.

Ethene does not react with $AgN{O}_3$ or $C{u}_2{C}_2$ solution.

Hence, the correct option is $\text{C}$