Question

Hardness of water can be detected using:

• A. $N{a}_{2}C{O}_3$
• B. Scum formed by lathering soap
• C. Dilute $H_{2}S{O}_4$
• D. Zn-Cu couple

Answer 1

The correct option is B Scum formed by lathering soap

Soap is defined as long chain salts of palmic acid, stearic acid and oleic acid. When soap is used with water it forms lather. If $C{a}^{2+}$ or $M{g}^{2+}$ ions are present in water (hardness) they tend to form scum with soap. Hence option (b) is the right answer.