Question

How does presence of ca2+and mg2+ ions in water lead to the formation of scum

Answer 1

OK
because charged calcium and magnesium particles (called ions ) present in the water react with soap to form an insoluble substance. Scum builds up on clothes, baths and sinks. ... When scum forms, sodium is replaced with a calcium or magnesium particle. The new substance, scum, does not dissolve in water.