NCERT Grade 7-Acids, Bases and Slats-Answers – MySchoolPage

NCERT Grade 7-Acids, Bases and Slats-Answers

NCERT Solutions for Class 7 Science

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1.     Acids are sour and turn blue litmus red. Bases are bitter and turn red litmus blue.

2.    Basic.

3.    Lichens. It is used as indicator.

4.    Distilled water is neutral.

5.    The reaction between an acid and a base is known as neutralization. Salts and water are produced in this process with the evolution of heat.

Acids + Bases → Salt + water

HCl + NaOH → NaCl + H2O

6.    (i) F       (ii) F        (iii) T              (iv) T          (v) F

7.    He can decide by the use of indicator. If the sample of drink turns red litmus blue, it is basic. If it does not turn blue litmus red, it is acidic. If it does not affect litmus, it is neutral.

8.    (a) Antacids are nothing but bases. When there is excess of acid in stomach, antacids are taken. Antacids neutralize the acids and relieve us.

(b) Ant injects an acid during bite which cuases the burning sensation. Calamine solution is basic in nature. It neutralizes the acid and relieves from the pain.

(c) Factory wastes contain both acidic and basic substances. These are harmful for the organisms living in water. So, these are neutralized.

9.    Turmeric solution turns red in contact with bases. It is not affected by acids and neutral substances.

At first we will identify the base.

The base is taken and turmeric is added. It will turn red. Then, one of the solution is added to it gradually. If the solution turns yellow again, the added liquid is Hydrochloric acid. Otherwise the added liquid is sugar solution.

10.  The solution may be neutral or basic. Both types of substance have no effect on blue litmus.

11.  (iv) Only d.

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