Ethyne gas is prepared by the reaction of water with calcium carbide (CaC2). Ethyne gas is a colourless gas.
Main Chemicals required
- Calcium Carbide (CaC2) [also known as calcium dicarbide] – A white/gray solid
- Acidified copper (II) sulfate solution
- Set up the apparatus as shown in the diagram.
- Place few pieces of calcium carbide in a Büchner flash.
- Add water from the dropping funnel, few drops at a time.
- Collect the gas produced in the test tube.
- Discard the first test tube as it a mixture of air and ethyne.
The ethyne gas burns with a luminous smoky flame with soot as a result of unburnt carbons.
Addition of Bromine Test
- Bromine water turns from yellow/red colour to colourless.
- The decolorisation of bromine is the standart test for unsaturation in a compound.
Addition of Acidified Potassium Permanganate (KMnO4) Test
- Purple colour to colourless.
- This is also used to test for presence of a C ≡ C triple bond (unsaturation).