SCIENCE CHAP 5. Acids, Bases and Salts WORKBOOK ANSWER

 5. Acids, Bases and Salts

1. Name the following.

a) Salt and water

b) Blue Litmus paper/ Methyl orange

c) Antacids

2. Identify the organic acid present in the following.

a) Tartaric acid

b) Lactic acid

c) Citric acid

3. Match the columns.

a) iii

b) i.

c) iv

d) ii

4. Assertion and Reason type questions.

a) A is true but R is false

b) Both A and R are true and R is correct explanation of the assertion.

5. Answer the following questions in brief.

a) Litmus is obtained from lichens. It is used as a natural indicator to test the

acidic or basic nature of solutions.

b) Methyl orange is a synthetic indicator. It is red to orange in colour in

acidic solutions. It changes to yellow in neutral and basic solutions.

c) Methyl orange is a synthetic indicator. It is red to orange in colour in

acidic solutions. It changes to yellow in neutral and basic solutions.

6. State one use for each of the following substances.

a) Ammonium sulphate is used as a fertiliser

b) Potassium nitrate is used for manufacturing of gun powder and fireworks,

as a fertiliser.

7. Give reasons for the following statements.

a) Acids are corrosive. They corrode most metals. Hence, acids should not be

stored in metal containers.

b) Calamine lotion (contains zinc carbonate) which neutralise the ant sting.

Calamine solution is applied on the skin after an ant bite.

8. Three test tubes (A, B and C) are shown in the figure. Each test tube contains

a different solution. Complete the table by predicting how each solution will

react with litmus, China rose and phenolphthalein as indicators.

Test tube	Nature of the solution	Litmus	China rose	Phenolphthalein
A	Acid	Blue litmus red	Dark pink	Colourless
B	Acid	Blue litmus red	Dark pink	Colourless
C	Base	Red litmus blue	Green	Pink

9. Read the situation given below and answer the questions that follow:
a) Several industries produce waste which contains strong acids. If these
wastes are directly allowed to flow into rivers, they will adversely affect
aquatic life.
b) To avoid this, wastes are first treated with bases like calcium oxide or
magnesium oxide to neutralise the harmful effects of the acids before
they are disposed into water bodies.
10.Fill in the crossword with the help of the clues provided.

Across 1. pH scale 5. hydrochloric acid 6. sour 8. bitter 9. neutral

Down 2. hydroxide 3. acid 4. basic 7. green

11.Higher Order Thinking Skills (HOTS) questions:
Turmeric is a natural indicator which reacts with a base and changes to red
colour. The soap solution is basic hence the turmeric stain turns red.
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