NCERT Solutions for Class 10 Science Chapter 2

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts intext questions answers given on Page 18, Page 22, Page 25, Page 28, Page 33 and chapter end Exercises in English Medium and Hindi Medium free to use.

Just like English Medium, Hindi Medium solutions of chapter 2 intext questions पेज 20 के उत्तर or पेज 24 के उत्तर or पेज 27 के उत्तर or पेज 31 के उत्तर or पेज 36 के उत्तर or अभ्यास के प्रश्न उत्तर are given to use free updated for new academic session 2020-21. Download CBSE Solutions Apps in Hindi & English Medium. These NCERT Solutions are based on latest CBSE Curriculum for 2020–2021.

NCERT Solutions for Class 10 Science Chapter 2

Class:10
Subject:Science – विज्ञान
Chapter 2:Acids, Bases and Salts

10th Science Chapter 2 Answers in English & Hindi Medium

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts Intext questions and chapter end exercises question answers are given below updated for new academic session 2020-21. NCERT Solutions are given in English and Hindi Medium free to use. Offline Apps 2020-21 are also in updated format free to download.




Define indicators. Name two natural indicators obtained from plants.

Indicators are substances which give different colour in acid or bases solutions. Natural indicators from plants are:
(a) Litmus,
(b) Vanilla extract.

What are antacids?

Antacids are mild alkalies. These are used for getting relief from acidity and indigestion and sometimes, even headache. When taken orally, it reacts with hydrochloric acid present in the stomach and reduces its strength by consuming some of it. For example, milk of magnesia is an antacid.

What are olfactory indicators? Give an example.

Olfactory indicators are substances which have different odour in acid and base solutions. For example, vanilla essence has characteristics pleasant smell in acid solution and no smell in alkali solution.

Tap water conducts electricity whereas distilled water does not. Why?

Tap water contains some impurities in the forms of salts. Due to presence of salts, it conducts electricity. Distilled water is free from all kinds of salts and hence does not conduct electricity.

While diluting an acid, why is it recommended that the acid should be added to water and not water into the acid?

When an acid is mixed with water, there is evolution of large amount of heat. Therefore, acid is slowly added to water. If on the other hand, water is added to acid, it might spill on your body and clothes due to explosion and evolution of sudden and large amount of heat.

What is meant by the term pH of a solution? The pH of rain water collected from two cities A and B was found to be 6 and 5 respectively. The water of which city is more acidic?

pH is a term which indicates whether a solution is acidic of basic and to what extent. Mathematically it is a measure of H+ ions concentration in water.
The rain water collected from city B is more acidic.

Tooth enamel is one of the hardest substance in our body. How does it undergo damage due to eating chocolates and sweets? What should we do to prevent it?

Sugar present in chocolates and sweets gets broken to acids by bacteria present in the mouth. This lowers the pH in the mouth. Tooth enamel is made up of calcium phosphate, which gets corroded when the pH in the mouth is below 5.5. To prevent tooth enamel from decay, toothpaste is used because it is alkaline and neutralises the acid produced in the mouth and helps to prevent lowering of pH in mouth.

Why are commercial samples of bleaching powder not completely soluble in water?

Bleaching powder is soluble in water. However, commercial samples of bleaching powder contains slaked lime that does not react with chlorine gas during the manufacture of bleaching powder. The insoluble part of bleaching powder is this white solid, i.e., slaked lime.




Questions for Practice on 10th Science Chpater 2

Question 1:
What is a neutralization reaction? Give some examples.
Answer 1:
When the effect of a base is nullified by an acid and vice versa, it is called neutralization reaction. In general, a neutralization reaction is written as:
Base + Acid ―> Salt + Water
Examples:
(a) Aqueous solution of base, NaOH is neutralized by aqueous hydrochloric acid.

neutralization reaction

(b) Aqueous solution of sulphuric acid is neutralized by aqueous solution of sodium hydroxide.

neutralization reaction 2

Question 2:
An alkali is an important base used for the laboratory work. Name the base and state how it can be prepared from common salt? What is this process called?
Answer 2:
An important alkali commonly needed for laboratory work is sodium hydroxide. It can be prepared from sodium chloride by the process of electrolysis. This is called chlor-alkali process.
Electrolysis of aqueous solution of sodium chloride: When electricity is passed through an aqueous solution of sodium chloride commonly called brine, it decomposes into chloride and sodium. Sodium is collected at the cathode where it reacts with water to form sodium hydroxide. Chlorine is formed at the anode and is collected as a gas.

electrolysis of NaCl

Cathode:

sodium hydroxide

At Anode:

Chlorine

The overall reaction is

chlor-alkali process



Questions from Board Papers

Question 1:
(a) How does baking soda helps to make cakes and bread soft and spongy? OR
Give reason: cake rise on adding baking powder.
(b) Write chemical equation for its preparation.
Answer 1:
(a) On heating , sodium bicarbonate decomposes to produce carbon dioxide. This causes biscuits and cakes etc. to expand and become light. The other constituents act as preservatives.
(b)

baking powder

Question 2:
Why does bleaching powder smell strongly of chlorine?
Answer 2:
Bleaching powder smells strongly of chlorine because it slowly reacts with carbon dioxide of air to evolve chlorine gas.

bleaching powder



Important Questions on 10th Science Chapter 2

Define indicators. Name two natural indicators obtained from plants.
Indicators are substances which give different colour in acid or bases solutions. Natural indicators from plants are: (a) Litmus, (b) Vanilla extract.
What are antacids?
Antacids are mild alkalies. These are used for getting relief from acidity and indigestion and sometimes, even headache. When taken orally, it reacts with hydrochloric acid present in the stomach and reduces its strength by consuming some of it. For example, milk of magnesia is an antacid.
What are olfactory indicators? Give an example.
Olfactory indicators are substances which have different odour in acid and base solutions. For example, vanilla essence has characteristics pleasant smell in acid solution and no smell in alkali solution.
What is a neutralization reaction? Give some examples.
When the effect of a base is nullified by an acid and vice versa, it is called neutralization reaction. In general, a neutralization reaction is written as:
Base + Acid ―> Salt + Water
Tap water conducts electricity whereas distilled water does not. Why?
Tap water contains some impurities in the forms of salts. Due to presence of salts, it conducts electricity. Distilled water is free from all kinds of salts and hence does not conduct electricity.
Why does distilled water not conduct electricity, whereas rain water does?
Distilled water is a pure form of water not containing any ionic species. Therefore, it does not conduct electricity. Rain water, being an impure form of water, contains many ionic species (dissolved in air) such as acids and therefore it conducts electricity.
Why do acids not show acidic behaviour in the absence of water?
Acids do not show acidic behaviour in the absence of water because the dissociation of hydrogen ions (H+ ) from an acid occurs in the presence of water only. It is the hydrogen ions (H+ ) that are responsible for the acidic behaviour.
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
The pH of milk is 6. As it changes to curd, the pH will reduce because curd is acidic in nature. The acids present in it decrease the pH.
Why does an aqueous solution of an acid conduct electricity?
Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of electricity.
Why does dry HCl gas not change the colour of the dry litmus paper?
Colour of the litmus paper is changed by the hydrogen ions. Dry HCl gas does not contain H+ ions. It is only in the aqueous solution that an acid dissociates to give ions. Since in this case, neither HCl is in the aqueous form nor the litmus paper is wet, therefore, the colour of the litmus paper does not change.
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
The process of dissolving an acid or a base in water is a highly exothermic one. Care must be taken while mixing concentrated nitric acid or sulphuric acid with water. The acid must always be added slowly to water with constant stirring. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.

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