Litmus test is used to distinguish between carboxylic acid and ethanol. When some blue litmus solution is added to the organic compound (to be tested), the colour of litmus solution turns red. It means the organic compound is acidic in nature, hence, it is a carboxylic acid. Ethanol has no effect on any litmus solution.

Litmus test: Some blue litmus solution is added to the organic compound (to be tested). If the blue litmus solution turns red, it shows that the organic compound is acidic in nature and hence it is a carboxylic acid (ethanoic acid). Ethanol has no effect on any litmus solution.