What is soap? Why are soaps not suitable for washing clothes when water is hard?

Asked by Omkar | 2nd Jan, 2018, 04:42: PM

Expert Answer:

  • Soaps are cleansing agents capable of reacting with water and dislodging the unwanted particles from clothes or skin.
  • The molecules of soap are sodium or potassium salts of long chain carboxylic acids.
  • A soap molecule has a tadpole-shaped structure.
  • At one end (long non-polar end) of soap, a molecule is a hydrocarbon chain which is insoluble in water but soluble in oil.
  • At the other end (short polar end) of soap molecule, there is a carboxylate ion which is hydrophilic i.e. water soluble but insoluble in oil.




  • Soap on mixing with water forms a concentrated solution and causes foaming.
  • The long non-polar end of soap gravitates towards and surrounds the dirt and absorbs the dust in it.
  • The short polar end with the carboxylate ion repels the water away from the dirt.
  • A spherical aggregate of soap molecules is formed in the soap solution in water and is called a micelle.
  • Thus, the soap molecule dissolves the dirt and our clothes get clean.

 soaps are not suitable for washing clothes when water is hard:

Soaps, when used with hard water, does not lather or produce foam easily because of the formation of a curdy precipitate or scum.

This scum is created when soaps react with the calcium and magnesium ions present in hard water.

Answered by Ramandeep | 3rd Jan, 2018, 09:52: AM