NCERT Class VII Science Solutions: Chapter 5-Acids, Bases and Salts Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 7:

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?


Dorji can use litmus test on these drinks. Just drop few drops of drink on litmus paper and take the decision according to the following:

  • If it turns blue, drink is basic.
  • If it turns red, drink is acidic.
  • If it turns green, drink is neutral.
As Showing in Images is a Result for Distilled Water Acid or …

Question 8:

Explain why:

  1. An antacid tablet is taken when you suffer from acidity.
As Showing in Images is a Result for a Antacid Tablet is Ta …
  1. Calamine solution is applied on the skin when an ant bites.
As Showing in Images is a Applied on the Skin when an Ant Bi …
  1. Factory waste is neutralized before disposing it into the water bodies.
As Showing in Images is a Result for the Wastes of Many Fact …


  1. Due to release of excess of hydrochloric acid, we suffer from acidity. An antacid tablet consists of a base like Milk of Magnesia (magnesium hydroxide) . It neutralizes the effect of excessive acid and brings relief.
  2. The sting of an ant contains formic acid which causes irritation on the skin. Calamine solution contains, zinc carbonate which is a base. Calamine solution neutralizes the acid effect of the ant bite when applied on the skin.
  3. The wastes of many factories contain acids. If they are allowed to flow into the water bodies, the acids will kill aquatic organisms. The factory wastes are, therefore, neutralized by adding basic substances.

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