Question

Which of the following is used to distinguish ethylene and acetylene ?

• A. Alkaline $KMn{O}_4$
• B. Bromine water
• C. Ammoniacal cuprous chloride
• D. Conc. $H_{2}S{O}_4$

Answer 1

Answer: (C)

On reaction with ammoniacal cuprous chloride, ethyne forms a red precipitate of copper acetylide. Ethyne can react with cuprous chloride since it has acidic hydrogen atoms. The carbon in ethyne is sp hybridized and is highly electronegative. Thus the hydrogen atoms attached to it are acidic.

Ethene on the other hand does not have acidic hydrogen atoms and does not react with ammoniacal cuprous chloride solution.