NCERT Solutions for Class 7 Science Chapter 5 – Acids, Bases and Salts, contains solutions to various questions in Exercise for Chapter 5. At the end of the Solutions, all the keywords and Notes which are important to understand NCERT Solutions for Class 7 Science Chapter 5- Acids, Bases and Salts, have been explained in a simple and easy to understand manner. NCERT Solutions for Class 7 help to check the concept you have learnt from detailed classroom sessions and application of your knowledge.
| Category | NCERT Solutions for Class 7 |
| Subject | Science |
| Chapter | Chapter 5 – Acids, Bases and Salts |
Download NCERT Solutions for Class 7 Science Chapter 5 – Acids, Bases and Salts
NCERT Solutions for Class 7 Science Chapter 5– Acids, Bases and Salts – Solutions to Question 1 to Question 5
Question 1:-
State differences between acids and bases.
Answer 1:-
| Acids have a sour taste | Bases have a bitter taste |
| Acids do not change the colour of turmeric | Bases change the colour of turmeric to red |
| Acids turn blue litmus red | Bases turn red litmus blue |
| They do not feel soapy on touching | They feel soapy on touching |
| Examples: acetic acid (vinegar), malic, acid (apple) etc. | Examples: Banking soda, caustic soda etc. |
Question 2:-
Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
Answer 2:-
Substances that turn red litmus blue are bases. Hence, ammonia is basic in nature.
Question 3:-
Name the source from which litmus solution is obtained. What is the use of this solution?
Answer 3:-
Litmus solution is obtained from lichens. It is a purple coloured solution which gives red colour in acids and blue colour in bases. Since it changes colour in presence of acids and bases, it is used as an indicator.
NCERT Solutions For Class 7 Science Chapter 5 – Acids, Bases and Salts – Video Explanation
Question 4:-
Is the distilled water acidic/basic/neutral? How would you verify it?
Answer 4:-
Distilled water is neutral in nature. This can be verified by litmus test. No change is observed in colour of litmus paper when it is dipped in distilled water.
Question 5:-
Describe the process of neutralisation with the help of an example.
Answer 5:-
The reaction of acids and bases to produce water and salt is called neutralisation.
For example-
Sodium hydroxide and sulphuric acid react together to form sodium sulphate (salt) and water.
Question 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)
Answer 6:-
(i) False
(ii) False
(iii) True
(iv) True
(v) False
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?
Answer 7:-
Dorji can decide which drink is to be served to whom by performing litmus test. Strips of blue and red litmus should be dipped in various drinks to decide nature of drinks. The drink which turns blue litmus red is acidic in nature, the drink which turns red litmus blue is basic in nature and the drink which has no effect on litmus paper is neutral in nature.
He can also taste a few drops from the bottles. Acidic drinks taste sour and basic drinks taste bitter.
Question 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.
Answer 8:-
(a)Antacid tablet contains a basic substance. When we take the tablet the acid in the stomach and base present in the tablet react together and neutralise the acid hence providing relief to the person
(b)Ant bites contain mild acid which causes irritation and inflammation on skin. When calamine solution is applied, the base present in the solution neutralises the acid by reacting with it hence providing relief from the bite.
(c)Water is neutral substance. The acid base proportion of water help aquatic life to survive in it. If factory waste is disposed without treating it, the fish and other animals in water will die. Hence, factory waste is treated first and then disposed into water bodies.
Question 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.
Answer 9:-
Turmeric indicator gives yellow colour in acidic and neutral solutions and red colour in basic solutions.
We can identify the three solutions by dropping a bit of each solution onto turmeric. The solution which turns it red is sodium hydroxide (base). Now we can add some amount of any one of remaining solutions into the base. If the new solution turns turmeric yellow then the solution that we added is hydrochloric acid (acid) and the remaining one is sugar solution. If the colour of turmeric does not change then the solution that we added is a sugar solution and the remaining one is acidic solution.
Question 10:-
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Answer 10:-
The solution may be basic or neutral in nature. The basic solution does not change the colour of blue litmus paper. Neutral solution does not change the colour of any litmus paper.
Question 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, c and d (iv) only d
Answer 11:-
(iv) only d
Topics Covered in Chapter 5 Acids, Bases and Salts Class 7 Science:-
- Acids and Bases
- Natural Indicators around us
- Neutralisation
- Neutralisation in Everyday Life
Important Terms Relevant to understand NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts:-
Acid: The substances which taste sour and turn blue litmus red are called acids. For example – acetic acid, hydrochloric acid etc.
Acidic: The substances which show all properties of acids are said to be acidic in nature.
Base: The substances which taste bitter and turn red litmus blue are called bases. For example – soap, baking soda etc.
Basic: The substances which show all properties of base are called basic in nature.
Indicator: The substances which change colour after coming in contact with acid or base are called indicators. For example – litmus, turmeric.
Neutral: The substances which do not show any properties of acids or bases and do not change the colour of indicators are called neutral in nature. For example – distilled water.
Neutralisation: The process in which acids react with bases which results in formation of salt and water is called neutralisation.
Salt: The substance formed along with after neutralisation reaction is called salt. For example – sodium chloride.
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