Question

Give a chemical test for to distinguish between 

1. Ethane, ethene and ethyne 

2. Ethanol and ethanoic acid.

Answer 1

1. Tests to distinguish between ethane, ethene and ethyne 

• Test — Br₂ water test: Pass the gas through Br₂ water, 

Ethane : Brown colour of Br₂ water is not discharged. 

Ethene : Brown colour of Br₂ water is discharged, 

Ethyne : Brown colour of Br₂ water is discharged.

• Test — Baeyer’s reagent : Pass the gas through Baeyer’s reagent (alkaline solution of KMnO₄ ). 

Ethane : Purple colour of Baeyer’s reagent is not discharged. 

Ethene : Purple colour of Baeyers reagent is discharged. 

Ethyne : Purple colour of Baeyers reagent is discharged.

• Test : Pass the gas through ammoniacal cuprous chloride solution. 

Ethane : No ppt. 

Ethene : No ppt. 

Ethyne : Red ppt. of copper acetylide is formed.

• Test : Pass the gas through ammonical silver nitrate solution. 

Ethane : No ppt. 

Ethene : No ppt. 

Ethyne : White ppt. of silver acetylide is formed.

2. Tests to distinguish between ethanol and ethanoic acid 

1. Test: Add a few drops of blue litmus solution to the given liquid. 

Ethanol: No change in colour. 

Ethanoic acid : Blue litmus turns red. 

2. Test: Add a pinch of sodium carbonate to the given liquid. Ethanol: No action. 

Ethanoic acid : Brisk effervescence with the evolution of CO₂.