Question

Name the water attracting ionic group in (a) a soap (b) a detergent.

Answer 1

Soap

• Soap is defined as the Sodium and Potassium salts of long-chain fatty acids.
• The general chemical formula of fatty acid is$\mathbf{RCOOH}$.
• A molecule of soap is made up of two parts that are, a polar part consists of ${\mathbf{COO}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$ and a nonpolar part consisting of a hydrocarbon chain.
• The polar part of the soap is water-soluble and the nonpolar part is oil-soluble.
• Therefore, the water-attracting ionic group in soap is ${\mathbf{COO}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$.

Detergent

• Detergent is the Sodium salt of a long chain Benzene Sulphonic acid that has cleansing properties in water.
• Synthetic detergents are prepared from the hydrocarbons that are obtained from petroleum.
• The ionic part in the synthetic detergent is $\mathbf{-}{\mathbf{SO}}_{\mathbf{3}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$ or $\mathbf{-}{\mathbf{OSO}}_{\mathbf{3}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$.
• Water attracting ionic group in detergent is $\mathbf{-}{\mathbf{SO}}_{\mathbf{3}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$or $\mathbf{-}{\mathbf{OSO}}_{\mathbf{3}}^{\mathbf{-}}{\mathbf{Na}}^{\mathbf{+}}$..