Question
How will you separate acetylene from a mixture of acetylene and ethylene?
Solution
Bubble the gaseous mixture through an ammoniacal solution of silver nitrate (Tollen's reagent) when acetylene products white precipitate of disilver acetylide. Ethylene will remain in the gaseous state and can be separated. 
The precipitate is separated, treated immediately with dilute HNO3 to get back acetylene in pure form.
