science - acids, bases and salts

Class 7 - Science

Acids, Bases and Salts

Q&A
Question:

Explain why:
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamine solution is applied on the skin when an ant bites.
(c) Factory waste is neutralised before disposing it into the water bodies.

Answer:

(a) We take an antacid such as milk of magnesia to neutralises the excessive acid released in stomach.
(b) Ant injects an acidic liquid (Formic acid) into the skin on biting which causes inflammation, to the skin. The effect of the acid can be neutralised by rubbing. Calamine solution which contains zinc carbonate which is very weak base and causes no harm to the skin.
(c) The wastes of factories contain acids. If acids are disposed off in the water body, the acids will harm the organisms. So factory wastes are neutralised by adding basic substances.



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Questions and Answers


Acids, Bases and Salts - Questions
1.

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?


Answer
2.

Describe the process of neutralisation with the help of an example.


Answer
3.

Explain why:
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamine solution is applied on the skin when an ant bites.
(c) Factory waste is neutralised before disposing it into the water bodies.


Answer
4.

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.


Answer
5.

Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?


Answer
6.

Name the source from which litmus solution is obtained. What is the use of this solution?


Answer
7.

Is the distilled water acidic/basic/neutral? How would you verify it?


Answer
8.

Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.


Answer
9.

State differences between acids and bases?


Answer
10.

Mark 'T' if the statement is true and 'F' if it is false:
(i) Nitric acid turns red litmus blue. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)
(id) Indicator is a substance which shows different colours in acidic and basic solutions. . (T/F)
(v) Tooth decay is caused by the presence of a base. (T/F)


Answer
11.

Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator. Which of these statements are correct?
(i) All four (ii) (a) and (d) (iii) (b) and (c) (iv) only (d)


Answer
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