Why are soaps not suitable for washing clothes with hard water?

Why are soaps not suitable for washing clothes with hard water?

Answer:

Soaps are not suitable for washing clothes with hard water because of two reasons:

  1. Soap reacts with the calcium and magnesium ions present in hard water to form insoluble precipitate called scum. This results in the wastage of soap.
  2. The sticky scum sticks to the clothes being washed and interferes with the cleaning ability of soap. This makes the cleaning of clothes difficult.