Course: Science - Class 7 (Chapter 01-10), Topic: Chapter 5 - Acids, Bases and Salts

Acids, Bases and Salts – Questions Page

Acids, Bases and Salts

Q37. 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?

Ans. Dorji can use red and blue litmus paper in order to test the drink.

i. The drink which does not change the colour of either red or blue litmus is the neutral drink.

ii. The drink which turns red litmus blue is the basic drink.

iii. The drink which turns blue litmus red is the acidic drink.

Q38. Complete the following table.

Ans.

Found in	Name of acid
Vinegar	Acetic acid
Ant’s sting	Formic acid
Citrus fruits such as oranges, lemons, etc.	Citric acid
Curd	Lactic acid
Spinach	Oxalic acid
Amla, Citrus fruits	Ascorbic acid (Vitamin C)
Tamarind, grapes, unripe mangoes, etc.	Tartaric acid

Q39. State few properties of base.

Ans. Properties of base

1. Bases are bitter in taste and soapy to touch.

2. Bases turn red litmus blue.

3. China rose indicator turns basic solutions to green.

4. Turmeric indicator turns basic solutions

5. Odorless (except ammonia).

6. Bases are slippery.

7. When the solution is basic, phenolphthalein gives a pink colour.

Q40. State few properties of acids.

Ans. Properties of acids

1. Acids are sour in taste

2. Acid turns blue litmus red.

3. China rose indicator turns acidic solutions to dark pink (magenta).

4. Turmeric indicator does not change its colour with acid

5. Gives burning sensation.

6. Acids are usually sticky.

7. When the solution is acidic, phenolphthalein remains colourless.

Q41 State the differences between acids and bases.

Ans. Difference between acids and bases

Acids	Bases
1. Acids are sour in taste	1. Bases are bitter in taste and soapy to touch.
2. Acid turns blue litmus red.	2. Bases turn red litmus blue.
3. China rose indicator turns acidic solutions to dark pink (magenta).	3. China rose indicator turns basic solutions to green.
4. Turmeric indicator does not change its colour with acid	4. Turmeric indicator turns basic solutions
5. Gives burning sensation.	5. Odorless (except ammonia).
6. Acids are usually sticky.	6. Bases are slippery.
7. When the solution is acidic, phenolphthalein remains colourless.	7. When the solution is basic, phenolphthalein gives a pink colour.

Q42. Three liquids are given to you. One is hydrochloric acid; another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.

Ans. Put a drop of each of the three liquids i.e. hydrochloric acid, sodium hydroxide and sugar solution on the turmeric indicator, the liquid which changes the colour of turmeric indicator to red is basic in nature, that is, sodium hydroxide.

Now, put a drop of sodium hydroxide on a drop of each of the other two liquids separately i.e. hydrochloric acid and sugar solution. After that, put the drops of these mixtures on turmeric indicator. The drop which will change colour of the turmeric indicator to red contains sugar solution. This is because the mixture of basic and neutral solution is basic in nature. On the other hand, the drop will not change the colour of turmeric indicator contains hydrochloric acid. This is because hydrochloric acid reacts with sodium hydroxide to form a neutral solution.