Question

what is scum ?how it is formed?

Answer 1

Scum is basically a stivky white substance which is insoluble in water. It mainly formed due to the reaction of magnesium and calcium ions with the sodium and potaasium salts of carboxylic acids.
when this reaction occurs,an insolube white precipitate is formed which is commonly called as scum.
Scum is normally formed in hard water as it contains magnesium ions or calcium ions, which on reaction with soap forms calcium stearate or magnesium stearate.
The calcium or magnesium stearate is a white precipitate and commonly known as scum.
2C₁₇ H₃₅ COO^- + Ca^₂₊ → Ca ( C₁₇ H₃₅ COO^- )₂