Question

For studying the cleansing capacity of soap in hard water students were asked to take the following precautions;
Do not use tap water
Don't use excess soap
Why?

Answer 1

hard water consists of Mg and K which react with with soap to form Mg and K salts which is a precipitate (s  c  u  m  ) and nullifies the cleansing action of soap

Answer 2

the upper one is exactly right