NCERT Science

Book: NCERT Science

Chapter: 5. Acids, Bases and Salts

Subject: Chemistry - Class 7th

Q. No. 8 of Exercise

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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 neutralized before disposing it into the water bodies.

a. Antacid is a substance that neutralizes the acidity in the stomach because it contains bases. We take antacid such as milk of magnesia, which contains magnesium hydroxide. These bases react with excess of acids released in stomach and neutralize their effects, thus giving us relief.

b. The sting of an ant contains formic acid. When an ant bites, it injects the formic acid into the skin which causes the burning sensation. The effect of acid can be neutralized by applying a base to it. Thus, by applying calamine solution which contain a base called zinc carbonate will neutralize the formic acid and relives us from the pain.

c. The wastes of many factories contain acids. If they are directly disposed into waters then, the water will become acidic and it will harm the aquatic life i.e. plants and animals inside the water. The acid can even kill the fish and the organism under water. Hence, these factory wastes are neutralized with basic substances before disposing to water bodies.


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