Check sibling questions

(i) You have three unlabelled test-tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identify the compounds in different test tubes by chemical tests using litmus paper and sodium metal.

(ii) Give the reason of formation of scum when soaps are used with hard water.

 

Answer

(i)

Solution

Blue litmus paper 

Red litmus paper

Sodium metal

Ethanol

No change

No change

H 2 gas released

Ethanoic acid

Red

No change

H 2 gas released

Soap

No change

Blue 

H 2 gas released

(ii) Soaps do not work in hard water because they react with calcium and magnesium ions and form a white sticky substance called scum.

CA Maninder Singh's photo - Co-founder, Teachoo

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CA Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo