Question

Soaps are not an effective cleansing agent in hard water. Explain.

Answer 1

Step 1:

Soaps contain Potassium $\left(\mathrm{K}\right)$ or Sodium $\left(\mathrm{Na}\right)$ salts of a long chain of carboxylic acids.

Soaps are biodegradable in nature.

Hard Water contains Calcium $\left({\mathrm{Ca}}^{2+}\right)$ and Magnesium $\left({\mathrm{Mg}}^{2+}\right)$ ion are present.

Step 2:

The cleansing action of soap depends on the hydrophilic and hydrophobic parts.

The ionic part of the soap is hydrophilic in nature and easily soluble in water.

The non-ionic part is hydrophobic in nature and dissolves in oil or grease.

In hard Water, Calcium and Magnesium ions are present.

Soaps are soluble in soft water but insoluble inorganic precipitate with Calcium and Magnesium ions are formed in hard water.

So, soaps are not effective in saline and hard water because soaps do not produce lather in hard Water.