Question

ordinary soap is wasted in hard water unlike synthesis detergent​

Answer 1

Ordinary soaps get wasted in hard water because hard water contains magnesium and calcium salts which when react with soap form scum which is insoluble in hard water therefore lot of soap gets wasted.

Whereas detergents doesn't react with magnesium and calcium to form scum they only react with dirt due to which they are best suited in hard water than soap.

Hope this answer is helpful.

Answer 2

soaps are made up potassium and sodium salt of long carbhylic acid when it reacts in hard water it does not form scum due presence of metals like Mg in hard water. But when detergents react in hard water it is formed of ammonium salt of long chain charbhylic acid so it doesn't reat with metal like Mg in hard water and forms scum quite quickly that's why soap is wasted in hard water.