Chapter – 5 Acid, Bases and Salt
A. Multiple Choice Questions (MCQ) Scientific/ Practical skills:
1. Baking soda solution turns pink china rose indicator green, it is __________ solution.
(a) an acidic (b) a basic (c) a neutral (d) none of these
Ans : b) a basic
2. A substance is sour in taste, not soapy to touch and has no effect on yellow turmeric solution.
It will affect______________ litmus paper.
(a) red (b) blue (c) green (d) black
Ans : b) blue
3. An acid reacts a base to produce_______________ .
(a) an acid (b) a base (c) only salt (d) salt and water
Ans : d) salt and water
B. Very Short Answer Questions:
1. Name two acids and bases.
Ans : Sulphuric acid and nitric acid are the names of two acids. Calcium hydroxide and magnesium hydroxide are the names of two bases.
2. How does litmus indicators work?
Ans : When the neutral litmus solution is added to an acidic solution, it turns red, and when it is added to a basic solution, it turns blue. It does not change its colour when we add a neutral solution to it.
3. Which acid is produced in our stomach?
Ans : Hydrochloric acid is produced in our stomach to digest the food we take.
C. Short Answer Type-I Questions:
1. Why do curd, lemon juice and tamarind taste sour?
Ans : Curd, lemon juice and tamarind taste sour because they all contain acids and acids are sour in taste. Curd contains lactic acid, lemon contains citric acid and tamarind contains tartaric acid.
2. What happens in the stomach when we eat very spicy food?
Ans : When we eat very spicy food our stomach produces a large amount of hydrochloric acid which leads to acidity in stomach. It is painful and can damage the wall of the stomach which can cause stomach ulcers, if not treated properly.
3. Why is an antacid tablet taken when you suffer from acidity?
Ans : Antacids are taken to cure the acidity because it contains weak bases that help to neutralise the excess acids present in our stomach.
D. Short Answer Type-II Questions?
1. Write one use each of (a) sulphuric acid, (b) hydrocholoric acid and (c) nitric acid.
Ans : a) Sulphuric acid is used in production of fertilizers.
b) Hydrochloric acid is used in production of batteries and fireworks.
c) Nitric acid is used in production of nitrate salts and coal tar.
2. Why should factory wastes be neutralised before discharging them into water bodies? Explain.
Ans : Most factory waste contain acids that can kill or cause harm to the aquatic organisms that live in the water bodies so, it must be treated and neutralised before dis charging them into water bodies.
3. Annie is playing in her garden with her friend, Ishrat. Suddenly, a bee bites Ishrat. Annie immediately brings soda and rubs it on the stung area.
(a) Why does Annie apply baking soda?
Ans : Annie applied baking soda on the stung area to neutralise the effect of the sting because being a base, baking soda nuutralises the formic acid injected by the bee.
(b) What value can you learn from Annie?
Ans : We can learn to help our friends and everyone in times of need as Annie did for friend Ishrat.
E. Long Answer Questions:
1. (a) How does the soil become too acidic in nature?
Ans : Acid rains, organic matter decay and excessive use of chemical fertilizers for harvesting high yielding crops can make the soil acidic in nature.
(b) What should be added in the soil when it is (i) too acidic and (ii) too basic?
Ans : (i) When the soil is too acidic, bases such as calcium oxide or calcium hydroxide can be added to neutralise the effect.
(ii) When the soil is too basic, organic matters such as manure or compost can be used because it is digested by bacteria and fungi to release acids.
2. Differentiate between acids and bases.
Ans : Some differences between acids and bases are as follows :
(i) Acids are sour in taste and bases generally taste bitter.
(ii) Acids turn blue litmus red while bases turn red litmus blue.
(iii) Acid has a pH value less than 7.0 when it is present in aqueous solution and base has a pH value higher than 7.0 when present in aqueous solution.
(iv) Acids are sticky when dissolved in water while bases are soapy and slippery when dissolved in water.
3. (a) What are organic acid?
Ans : The acids that are found in plants and animals are called organic acids.
(b) Name any two organic acids.
Ans : Citric acid and lactic acid are two organic acids.
(c) How are mineral acids different from organic acids?
Ans : Mineral acids are made with minerals of the earth by humans. Mineral acids are very strong and dangerous while organic acids are harmless and mostly useful to us.
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