NCERT Solutions for Class 7 Science Chapter 5 Acids, Bases and Salts
Subject specialists have designed NCERT solutions for Science Class 7 Chapter 5 which includes thorough solutions for reference. These solutions are updated according to the latest CBSE syllabus for 2012-22 and are provided in easy language for understanding. Tips and tricks are also provided.
These solutions are provided so a student can clear his doubts and get help with deep understanding of the concept. Also you can refer them to make the chapter notes and revisions notes. PDF of this can also be downloaded from website.
1. State differences between acids and bases.
1) They are sour in taste 1) They are bitter in taste
2) They turn blue litmus to red 2) They turn red litmus to blue
3) Generally acids give H+ ions when they 3) Generally bases give OH– ions when they
dissolved in water Ex : Hydrochloric acid dissolve in water Ex ; Sodium Hydroxide (NaOH)
(HCl), Sulphuric acid (H2SO4), Ammonium Hydroxide (NH4OH)
Nitric acid (HNO3) etc… Calcium Hydroxide [Ca(OH)2] etc….
2. Ammonia is found in many house hold products, such as window cleaners. It turns red litmus to blue. What is its nature?
Ans : Ammonia turns red litmus to blue due to its basic nature.
3. Name the source from which litmus solution is obtained. What is the use of this solution ?
Ans : 1) Litmus solution is extracted from lichens.
2) It has a mauve (purple) colour in distilled water.
3) When added to an acidic solution, it turns Purple to Red.
4) When added to a basic solution, it turns Purple to Blue.
5) It is available in the form of a solution, (or) in the form of strips of paper known as litmus paper.
4. Is the distilled water acidic / basic / neutral ? How would you verify it ?
Ans : 1) The distilled water is neutral.
2) Put a drop of distilled water on the strips of red and blue litmus papers, each with the help of a dropper.
3) We observe that colour of the litmus paper is not changed.
4) Water is neither acidic nor basic i.e., water is neutral.
5. Describe the process of neutralisation with the help of an example.
Ans : 1) The reaction between an acid and a base is known as neutralisation.
2) Salt and water are produced in this process with the evolution of heat.
Acid + Base Salt + Water
(Heat is evolved)
Ex : Hydrochloric acid + Sodium Hydroxide Sodium chloride + Water
HCl + NaOH NaCl + H2O
6. Mark ‘T’ if the statement is true and ‘F’ if it is false.
Ans : i) Nitric acid turns red litmus blue (T/F) – False
ii) Sodium hydroxide turns blue litmus red (T/F) – False
iii) Sodium hydroxide and Hydrochloric acid neutralise each other and form salt and water
(T/F) – True
iv) Indicator is a substance which shows different colour in acidic and basic solutions (T/F) – True
v) Tooth decay is caused by the presence of a base (T/F) – False
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 wants neutral drink. How will Dorji decide which drink is to be served to whom ?
Ans : 1) Dorji tests the nature of these few bottles of soft drink with litmus paper.
2) Which soft drink bottle turns blue litmus to red i.e., acidic soft drink
3) Which soft drink bottle turns red litmus to blue i.e., basic soft drink
4) Which soft drink bottle does not change litmus paper i.e. neutral soft drink.
5) Finally he distributed these three different Acidic, basic and neutral soft drink bottles
individually to the customers.
8. Explain why :
a. An antacid tablet is taken when you suffer from acidity.
Ans : 1) Our stomach contains Hydrochloric acid.
2) It helps us to digest food.
3) Too much of acid in the stomach causes indigestion some times. Indigestion is painful.
4) To relieve indigestion, we take an antacid such as Milk of Magnesia, Which contains Magnesium hydroxide.
5) It neutralises the effect of excessive acid.
b. Calamine solution is applied on the skin when an ant bites.
Ans : 1) The sting of an ant contains Formic acid.
2) When an ant bites, it injects acidic liquid into the skin i.e, Formic acid.
3) The effect of the acid can be neutralised by rubbing moist baking soda (Sodium hydrogen
carbonate) or Calamine solution, Which contains Zinc carbonate.
c. Factory waste is neutralised before disposing it into the water bodies.
Ans : 1) The wastes of many factories contain acids.
2) If they are allowed to flow into the water bodies those acids will kill fish and other organisms
3) There fore the factory wastes are neutralised by adding basic substances.
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 ?
Ans : Turmeric is a natural indicator present in yellow colour. In acidic medium it remains same, where as in basic medium turns to reddish brown colour.
When we dip turmeric indicator into three test tubes containing HCl, NaOH and Sugar solution, in which test tube it turns to reddish brown it is NaOH. Then use the same Indicator and dip in remaining two solutions, in which test tube it turns back to yellow it is HCl and the remaining solution is sugar solution.
10. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution ? Explain.
Ans : The nature of the solution may be neutral or basic because the solutions which do not change the colour of blue litmus, are either neutral or basic.
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 b iii) b and c iv) only d
Ans : iv) only d
Important topics covered in NCERT Solutions for class 7 chapter 5 Acids, Bases and Salts
|Acids And Bases
|Natural Indicators Around Us
|Neutralisations In Everyday Life
The combination of acid and base forms the salt which can either be acidic, basic or neutral in nature. This process is called as neutralisation. Neutralization is consider as most important for exams. To avoid confusion between acids, bases and salts students are advised to make tables for that.
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Frequently Asked Questions on NCERT Solutions of this Chapter
From which source the litmus solution is obtained in these NCERT Solutions?
Litmus solution is obtained from Lichens. It is generally used as an indicator to determine the basic and acidic nature of solution. Students who are disable to understand this topic can refer to the NCERT Solutions from Infinite learn. The solutions are designed by subject matter experts having rich in experience in their subject to help students score well in the exam. Both chapter wise and exercise wise format of solutions can be utilize by the students to get their queries cleared instantly.
What are the benefits of using NCERT solutions?
NCERT solutions by Infinite Learn is designed strictly according to the latest CBSE syllabus and it is the best way to study this chapter containing all the important points and formulas. The subject matter experts designed these NCERT solutions with an aim to make the learning process a most convenient way.
What concepts can I learn from these NCERT Solutions?
The concepts like –
1. Acids And Bases
2. Natural Indicators Around Us
4. Neutralisations In Everyday Life