Question

Hardness of water can be detected by 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 in general, can be taken to be Sodium Stearate. 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. As a result, lather formed is lower when compared to that of soft water. Hence option (b) is the right answer.