Question

A differentiate between soap and detergent b)explain why soap from scum with hard water whereas detergents do not

Answer 1

Soaps are Sodium or Potasium salts of long chain carboxylic acids and have general formula RCOONa.
whereas
Detergents are usually ammonium or sulphonate salts of long chain carboxylic acids.

Soaps forms come with hard water because of the reaction of soap with the calcium and magnesium salt which cause the hardness of water. Whereas the charged ends of detergents do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they are more effective in hard water.

Answer 2

Soaps :

Soaps are sodium or potassium salts of long chain carboxylic acids.

Soaps have lesser cleansing action or quality as compared to detergents.

Soaps are made from animal or plant fats.

Soaps are more biodegradable.

Detergents :

Detergents are ammonium or solphonate salts of long chain carboxylic acids.

Detergents have better cleansing action as compared to soaps.

Detergents are made from petrochemicals. Detergents are less biodegradable.

(b) Hard water contains ions of calcium and magnesium which react with soap molecules to form insoluble precipitates called soap scum.