Chapter 3: Let us answer these (Page-40)

Q1. From the observe facts draw your conclusion comparing with the results of the activity given in the following table: 

Sample Solution	Phenolphthalein	Blue Litmus	Red Litmus	Methyl orange
Hydrochloric acid	Colourless	Red	Red	Pink (Red)
Sulphuric  acid	Colourless	Red	Red	Pink (Red)
Acetic acid	Colourless	Red	Red	Pink (Red)
Oxalic acid	Colourless	Red	Red	Pink (Red)
Sodium hydroxide	Pink	Blue	Blue	Yellow (Orange)
Sodium carbonate	Pink	Blue	Blue	Yellow (Orange)
Ammonium hydroixde	Pink	Blue	Blue	Yellow (Orange)

Ans: The conclusion can be made as the following:

         a) All acids can change the colour of Blue litmus and methyl orange, but no change in Red litmus and phenolphthalein.

         b) All bases can change the colour of phenolphthalein, Red litmus and Methyl orange, but no change in the Blue litmus.

Q2. Suggest the usefulness of turmeric powder as an indicator. 

Ans: Usefulness of turmeric powder as an indicator:

Turmeric powder is a natural indicator beacuse it shows the acidic and basic solutions by changing their colours:

i) In acidic solution solution, the colour of the turmeric powder (i.e. yellowish colour) is changed into pink.

ii) In basic solution, the colour of the turmeric powder (i.e. yellowish colour) is changed into pink-orangee(i.e brown).

Q3. Is Sodium chloride Solution acidic or base?

Ans: Sodium chloride solution is neither acidic nor basic because the colour of litmus remains unaffected in this solution (or it conatins no replaceable hydrogen nor hydroxide ions).

Read this too