In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
Assertion : Sodium chloride is added to precipitate soap after saponification .
Reason : Hydrolysis of esters of long chain fatty acids by alkali produces soap in colloidal form.
Answer & explanation
Correct answer: option 1
Sodium chloride is added to precipitate soap after saponification. Salt is added to decrease the solubility of soap and it help precipitate out (or salt out) from the aqueous solution.
Hydrolysis of esters of long chain fatty acids by alkali produces soap in colloidal form.
Thus, when oils and fats (glycerides) are heated with a solution of sodium hydroxide, they break down to sodium salt of the respective fatty acid (called soap) and glycerol The process is called saponification.