Question

What contains dissolved compounds of calcium and magnesium which react with soap forming a scum instead of a useful lather

Answer 1

Answer:

Permanent hard water is also responsible for the bathtub "ring," or soap scum, seen after showering or bathing. As previously mentioned, permanent hard water contains calcium and magnesium cations. These cations react with soap to form insoluble compounds that are then deposited on the sides of the tub.