Question

(a) Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom? [3 marks]

(b) Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results. [2 marks]

Answer 1

(a) Dorji can decide which drink is to be served to whom in the following ways:

• Take red and blue litmus paper and test the nature of all the soft drinks with them. [1 mark]
• The drink in which red litmus paper turns blue is basic in nature. and the drink in which blue litmus paper turns red is acidic in nature. [1 mark]
• The drink in which both red and blue litmus paper shows no changes in colour neutral in nature. [1 mark]

(b) The possible cause for the variation in the colour of the solutions A, B and C after adding china rose solution to them is as follows:

• China rose solution is light pink in colour in neutral solutions, turns dark pink in acidic solutions and green in basic solutions. [1 mark]
• Therefore, solution A which turned dark pink must be acidic in nature, solution B which turned green must be basic in nature and solution C which didn't show any colour change must be neutral in nature. [1 mark]