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NCERT Solutions Class 7 Science Chapter 5: Acids, Bases and Salts

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The NCERT Solutions Class 7 Science Chapter 5 Acids, Bases and Salts is crucial due to the applications it has in science and the impact it puts on your future studies as well as on CBSE Class 7 examinations. The NCERT solutions provided here are comprehensive and help to understand the concepts for students who are struggling to remember the concepts of Acids, bases and salts for a longer time.

NCERT Solutions for Class 7 Science Chapter 5 by Swiflearn are by far the best and most reliable NCERT Solutions that you can find on the internet. These NCERT Solutions for Class 7 Science Chapter 5 are designed as per the CBSE Class 7 Science Syllabus. These NCERT Solutions will surely make your learning convenient & fun. Students can also Download FREE PDF of NCERT Solutions Class 7 Science Chapter 5.

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NCERT Solutions Class 7 Science Chapter 5 Acids, Bases and Salts PDF

1. State differences between acids and bases.

Solution:
The differences between acids and bases are as follows:
Acids                                                                           Bases
They turn blue litmus red.                                             They turn red litmus blue.
They are sour in taste.                                                  They are bitter in taste.
They do change the colour of turmeric.                        They change the colour of                                                                                          turmeric to  red.

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

Solution:
Ammonia is basic in nature as it turns red litmus blue.

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

Solution:
Litmus is derived from lichens. Litmus is used to find out whether the given solution is acidic or basic.

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

Solution:
Distilled water is neutral. This can be verified by using blue and red litmus paper. The colour of neither red nor blue litmus changes when dipped in distilled water.

5. Describe the process of neutralization with the help of an example.

Solution:
The reaction between an acid and a base is known as the neutralization reaction. In such a reaction, both acids and bases get neutralized.
For example, when sodium hydroxide (NaOH) is added to hydrochloric acid (HCl), sodium  chloride (NaCl) and water (H2O) are obtained.
NaOH + HCl → NaCl + H2O + Heat

6. 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)
(iv) 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).

Solution:
(i) Nitric acid turns red litmus blue. (F)
(ii) Sodium hydroxide turns blue litmus red. (F)
(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T)
(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T)
(v) Tooth decay is caused by the presence of a base. (F).

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?

Solution: Dorji can taste a few drops of the soft drinks and decide which drink is to be served to whom.
An acidic solution is sour in taste, basic solution is bitter in taste, and the neutral solution has no taste.
Apart from tasting, Dorji can also use litmus paper to test the nature of soft drink.
An acidic solution turns blue litmus red, a basic solution turns red litmus blue, and the neutral solution does not change the colour of either red or blue litmus.

8. 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.

Solution:
1. The antacid tablet contains base like milk of magnesia which neutralises the acid produced in the stomach. Hence, it is used while suffering from acidity.
2. Ant bites inject formic acid inside the skin. Calamine consists of Zinc carbonate which is basic in nature. Thus, calamine neutralises the effect of formic acid and brings relief to the affected person.
3. Factory wastes can cause harm to the aquatic life as they are acidic in nature. Hence, the waste is neutralised by using a base before disposing it into the water bodies.

9. 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.

10.Solution:
The following procedure can be performed in order to identify the liquids:
Add solution to containers with turmeric indicator.
The turmeric indicator turns red when a basic solution is added to it. If the solution is sodium hydroxide, the turmeric indicator would turn red.
Now, slowly add solution 2 to the red turmeric indicator.
If the colour of the turmeric indicator turns yellow again, it means that neutralization has taken place and solution 2 is hydrochloric acid.
If the colour of turmeric indication does not change on adding solution 2, it means that solution 2 is neutral. That is solution 2 is sugar solution.

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

Solution:
If the colour of blue litmus does not change when it is dipped in a solution, implies that the solution can either be basic or neutral in nature.

12.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, c and d (iv) only d

Solution:
Only statement (d) is correct.

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