A student puts a drop of reaction mixture of a saponification reaction first on a blue litmus paper and then on a red litmus paper. He may observe that :

(a) There is no change in the blue litmus paper and the red litmus paper turns white.

(b) There is no change in the red litmus paper and the blue litmus paper turns red.

(c) There is no change in the blue litmus paper and the red litmus paper turns blue.

(d) No change in colour is observed in both the litmus papers.

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Solution

(c) There is no change in the blue litmus paper and the red litmus paper turns blue.
Saponification which basically refers to the reaction between metallic alkali and a fat or oil to produce soap. It involves the hydrolysis of an ester under acidic or basic conditions and results in the formation of an alcohol and a salt of carboxylic acid.
We also know that the litmus paper is a kind of filter paper which is treated with water soluble dye and it can be used as a pH indicator. So, under basic conditions, the red litmus paper turns blue and under acidic conditions, blue litmus paper turns red.
Soaps are slightly basic because they are the salts of strong bases and weak acids.
Base does not affect blue litmus because it doesn’t consist of acidic ions which can turn blue litmus red.

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Q. A student puts a drop of the reaction mixture of a saponification reaction first on a blue litmus paper and then on a red litmus paper. He may observe that:

Q. What do we observe on pouring acetic acid on red blue litmus papers ?
(a) Red litmus remains red and blue litmus turns red.
(b) Red litmus turns blue and blue litmus remains blue.
(c) Red litmus turns blue and blue litmus turns red.
(d) Red litmus becomes colourless and blue litmus remains blue.

When a red litmus paper is dipped in the aqueous solution of $X$ there is no change in colour.
When a blue litmus paper is dipped in the same solution it turns red.
Which among the following options can be the chemical $X$ ?

Q. Dry ammonia has no action on litmus paper, but a solution of ammonia in water turns red litmus paper blue. Why?

Q. Read the following statements:
I. When a red litmus paper is dipped into reaction mixture of a saponification reaction, it turns blue and the reaction is exothermic.
II. When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is exothermic.
III. When a red litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is endothermic.
IV. When a blue litmus paper is dipped into reaction mixture of a saponification reaction, its colour does not change and the reaction is endothermic.
Which of the above statements are correct?

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