While studying the saponification reaction, what do you observe when you mix an equal amount of colourless vegetable oil and 20% aqueous solution of NaOH in a beaker?
(a) The colour of the mixture has become dark brown
(b) A brisk effervescence is taking place in the beaker
c) The outer surface of the beaker has become hot
(d) The outer surface of the beaker has become cold
Answer
Saponification is the conversion of fat, oil or lipids into soap and alcohol by the action of an aqueous alkali (NaOH).
A whitish suspension is seen. Since no CO 2 is evolved, no brisk effervescence is seen.
The outer surface of the beaker becomes hot because it is an exothermic reaction i.e. heat is released.
Checking the options
- (a) The colour of the mixture has become dark brown - This is not observed. A whitish suspension is seen as a result of the reaction.
- (b) A brisk effervescence is taking place in the beaker - This is not observed since carbon dioxide is not evolved as the result of the reaction.
- (c) The outer surface of the beaker has become hot - This is observed.
- (d) The outer surface of the beaker has become cold - This is not observed.
Therefore, the correct option is (c) the outer surface of beaker becomes hot
