Question

What is Sodium Hydroxide in soap?

Answer 1

1. Soap is the Sodium or Potassium salts of long-chain fatty acids (Carboxylic acids).
2. Soap contains cleansing properties in water.
3. As the Fats and vegetable oil are naturally occurring esters of long chain fatty acids and an alcohol called Glycerol are the main constituents that help in making the soap.
4. The reaction of Soap with Sodium hydroxide$\left(\mathrm{NaOH}\right)$ in the presence of heat produces soap and Glycerol$\left(\mathrm{R}-\mathrm{OH}\right)$.
5. $\underset{\left(\mathrm{Ester}\right)}{\mathrm{Fat}\mathrm{or}\mathrm{oil}}+\underset{\left(\mathrm{alkali}\right)}{\mathrm{Sodium}\mathrm{hydroxide}\left(\mathrm{s}\right)}\to \underset{(\mathrm{Sodium}\mathrm{salt}\mathrm{of}\mathrm{fatty}\mathrm{acid})}{\mathrm{Soap}}+\underset{\left(\mathrm{Alcohol}\right)}{\mathrm{Glycerol}}$
6. The process is so called saponification reaction.
7. The Sodium hydroxide used in the reaction is good for the skin as it maintains the pH balance of the skin.