Ethene and ethane.

Question

1. Ethene and ethane.
2. Ethyne and ethane.
3. Alkanes, alkenes and alkynes.

Answer 1

1. Ethene gas decolourises bromine solution and potassium permanganate solution. But, ethane gas does not change the colour of these solutions.
2. Ethyne gas forms a white precipitate with ammonical solution of silver nitrate and red ppt. with ammonical solution of copper (I) chloride. But, ethane does not respond to such tests.
3.

S.No.	Test	Alkanes	Alkenes	Alkynes
(i)	Bromine Test Add a few drops of sol. of bromine in carbon tetra-chloride to the hydrocarbon.	No change takes place.	The red colour of bromine is decolorised.	The red colour of bromine is decolorised.
(ii)	Alkaline Potassium Permanganate Test: Add a few drops of alkaline pot. permanganate sol. To the hydrocarbon.	No change takes place.	The purple colour of Potassium permanganate is decolorised.	The purple colour of potassium permanganate is decolorised.
(iii)	Ammoniacal Cuprous Chloride Test: Add a few drops of ammoniacal cuprous chloride sol. to thehydrocarbon.	No change takes place.	No change takes place.	A red ppt. of copper acetylide is formed.

Answer 2

1. Ethene gas decolourises bromine solution and potassium permanganate solution. But, ethane gas does not change the colour of these solutions.
2. Ethyne gas forms a white precipitate with ammonical solution of silver nitrate and red ppt. with ammonical solution of copper (I) chloride. But, ethane does not respond to such tests.
3.

S.No.	Test	Alkanes	Alkenes	Alkynes
(i)	Bromine Test Add a few drops of sol. of bromine in carbon tetra-chloride to the hydrocarbon.	No change takes place.	The red colour of bromine is decolorised.	The red colour of bromine is decolorised.
(ii)	Alkaline Potassium Permanganate Test: Add a few drops of alkaline pot. permanganate sol. To the hydrocarbon.	No change takes place.	The purple colour of Potassium permanganate is decolorised.	The purple colour of potassium permanganate is decolorised.
(iii)	Ammoniacal Cuprous Chloride Test: Add a few drops of ammoniacal cuprous chloride sol. to thehydrocarbon.	No change takes place.	No change takes place.	A red ppt. of copper acetylide is formed.