Class 10 Science Chapter 2 Acids, Bases and Salts - Previous years appeared questions

    Class 10 Science 

   Chapter 2 Acids, Bases and Salts 

    Previous years appeared questions 

     Multiple Choice Questions 

1. As the pH value of a neutral solution increases (March 2020)

(A) basic property decreases and number of OH− ions increases

(B) acidic property increases and number of H+ ions decreases

(C) basic property increases and number of OH− ions increases

(D) acidic property decreases and number of H+ ions increases. 

Ans. : (C) basic property increases and number of OH− ions increases

2. The chemical equation that represents neutralization reaction among the following is  (March 2019, KSEEB MP 22-23)

Ans: C

3. As the pH value of a solution increases. (KSEEB MQP 2021)

A) number of H+ ions increases

B) number of OH– ions increases

C) number of OH– ions decreases

D) equal number of H+ and OH– ions

Ans: B) number of OH– ions increases

4. The gas liberated when an acid reacts with a metal is: (KSEEB MQP 2020)

A. Hydrogen                  B. Chlorine

C. Carbon dioxide        D. Nitrogen dioxide

Ans: A. Hydrogen 

5. The substance that converts red litmus paper into blue colour is (KSEEB MQP 22-23)

(A) KOH Solution

(B) distilled water

(C) dilute solution of HCl

(D) concentrated solution of HNO3

 

Ans : (A) KOH Solution 

6. The pH value of a solution that turns blue litmus paper into red colour is (May 2025)

(A) 5        (B) 7    (C) 9       (D) 14

Ans. :   (A) 5

7. The chemical formula of bleaching powder is (MQP-3 25-26)

(A) NaCl              (B) Na2CO3 

 (C) CaCO3        (D) CaOCl2 

Ans: (D) CaOCl2 

8. As the pH value of a neutral solution increases, (MQP - 4 25-26)

(A) basic property decreases and number of OH− ions increases. 

(B) acidic property increases and number of H+ ions decreases.

(C) basic property increases and number of OH− ions increases. 

(D) acidic property decreases and number of H+ ions increases. 

Ans: (C) basic property increases and number of OH− ions increases. 

   

    One Marks Questions 

1. Write any two uses of Plaster of Paris. (March 2022)

Ans. :  

• Plaster of Paris is used in :
• Supporting fractured bones
• Making toys
• Decorative materials
• Making smooth surfaces. ( Any two )

2. Name the acid present in the stinging hair of nettle leaves. (March 2019)

Ans:

Formic acid (Methanoic acid)

3. Name the ions responsible for acidic and basic natures of

the substances.(june 2023)

Ans. :

★ Acidic — H+ / H3O+ / Hydrogen / Hydronium

★ Basic — OH− Hydroxyl / Hydroxide

4. Write any two uses of washing soda. (April 2024)

Ans. : 

★ In glass, soap and paper industries. 

★In the manufacture of sodium compounds such as borax. 

★ As a cleaning agent for domestic purposes. 

★ For removing permanent hardness of water. (Any two)

5. How is concentrated acid diluted ? (April 2025)

Ans. : By adding the acid slowly to the water with constant stirring. 

6. By adding the acid slowly to the water with constant stirring. Aqueous solution of nitric acid (HNO3) shows acidic nature but the solution of alcohol does not show this nature. Why? (May 2025)

Ans. :

★ Nitric acid releases H+ in aqueous solution.

★ Alcohol does not release H+ ions in aqueous solution.

7. The solution of baking soda is applied on the part of the skin stung by the stinging hairs of the leaves of the nettle plant. Give reason. (May 2025)

Ans. :

Stinging hairs of nettle leaves inject methanoic acid to the skin causes burning.

To get relief from this burning, solution of baking soda is applied as it is a mild base ( neutralises the action of acid )

8. How do you detect a base using blue litmus paper? (MQP-1 2025-26)

Ans: The colour of litmus paper does not change when dipped in a basic solution. 

9. Hydrochloric acid is considered as a strong acid. Why? (MQP-2 25-26)

Ans: 

★ In water, hydrochloric acid completely dissociates into ions. 

★ Hydrochloric acid forms more H+ ions in water.                      (Any one) 

    Two Marks Questions 

1. The pH values of A, B and C solutions are 5, 6 and 7 respectively. Which of these solutions is more acidic in nature ? Why ? (March 2022)

Ans. :  

• Solution A is more acidic.
•  As it has more + H ions.

2. Draw the diagram of the arrangement of apparatus to show that acid solution in water conducts electricity and label the battery. (Sep 2020)

Ans:

3. Draw the diagram of the arrangement of apparatus showing the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning and label the zinc granules. (Sep 2020)

Ans:

4. Agricultural scientists have suggested to add a certain amount of lime powder to an agricultural field. What may be the reasons for this ? Explain. (March 2020)

Ans. :

★ Plants require a specific pH range for their healthy growth.

★ Soil of his land is acidic.

★ Lime powder is a base.

★ So adding lime powder to the soil, decreases the acidic property / soil is neutralised. 

5. Draw the diagram of the apparatus to show that acid solution in water conducts electricity. Label the following parts : i) Dil. HCl solution ii) Rubber cork. (March 2020)

Ans:

6. Draw the diagram of arrangement of the apparatus to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts : i) Test tube ii) Soap solution. (March 2020)

Ans. :

7. Name the gas liberated when an acid reacts with metallic carbonate. Write the chemical equation of the reaction when this gas is passed through lime water. What is the colour of the precipitate obtained in this reaction ? (June 2019)

Ans:

★ When an acid reacts with metallic carbonate , carbon dioxide gas is liberated.

★ When carbon dioxide gas is passed through lime water, calcium carbonate is produced as a white precipitate.

★ The chemical equation is :

Ca(OH)2 + CO2→ CaCO3 + H2O

8. Give scientific reason :

(i) While diluting an acid, the acid should be added to water.

(ii) Plaster of Paris should be stored in a moisture-proof container. (June 2019)

Ans:

★ adding water to a concentrated acid releases a large amount of heat, which can cause an explosion and acid burns on the skin, clothing, and other body parts.

★ Plaster of Paris in contact with moisture (water) changes to solid hard mass, gypsum. Therefore, it gets wasted. Hence it should be stored in moisture proof container

9. Draw the diagram of arrangement of apparatus used to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts. (i) Soap solution (ii) Delivery tube. (March 2019)

Ans:

10. There is no change in the colour of red litmus and blue litmus paper when introduced into an aqueous solution of sodium chloride. After passing direct current through the same solution, red litmus changes to blue colour. Which product is responsible for this change ? Mention any two uses of this product. (March 2019)

Ans:

★ Sodium Hydroxide is responsible for this change. Use of this product is:

★ Sodium hydroxide is used in drain and oven cleaners

★ It is also commonly used in the manufacture of fabric, plastic wrap, paper and soap

11. Write the molecular formula and two uses of each of the following compounds: a) Washing soda b) Bleaching powder (KSEEB MQP 2021)

Ans:

a)

Molecular formula : Na2CO3

Uses:

★ used in soap, glass and paper industries.

★ It helps in the removal of permanent hardness of the water.

b)

Molecular formula : CaOCl2

Uses

★ for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry.

★ as an oxidising agent in many chemical industries

★ to make drinking water free from germs. ( Any two uses)

12. Name the two gases liberated in Chlor-alkali process. Write one use of each. (KSEEB MQP 2021)

Ans:

two gases liberated in Chlor-alkali process are Hydrogen and Chlorine gas

Uses of chlorine

★ It is used in the production of bleaching powder.

Uses of Hydrogen gas

★ It is used as fuel for rockets.

13. The gas liberated when sodium carbonate reacts with dilute hydrochloric acid is passed through lime water, a white precipitate is formed. But when the same gas is passed through lime water in excess, precipitate is not visible. Why? (KSEEB MQP 2020)

Ans:

because of formation of calcium hydrogen carbonate. As calcium hydrogen carbonate is soluble in water, thus, the milky colour of solution mixture disappears.

14. What is the chemical name of bleaching powder ? Write any two uses of it. (KSEEB MQP 22-23)

Ans :

chemical name : Calcium oxy chloride( CaOCl2)

Uses : (i) for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry;

(ii) as an oxidising agent in many chemical industries; and

(iii) to make drinking water free from germs.                 (Any Two)   

15. What is concentrated acid? Name the acid present in the stinging hair of nettle leaves. (KSEEB MQP 22-23)

Ans :

★ Acid with more concentration of H+ /H3O+ ions per unit volume.

★ Methanoic acid    

16. Simultaneously red and blue litmus papers are dipped in the brine solution and in the aqueous product produced by subjecting that solution to electrolysis. What changes do you observe in litmus papers ? Support your answer with reasons.  (April 2024)

Ans: 

No colour change is observed in the litmus papers dipped in the brine solution. Because it is a neutral solution. 

Red litmus paper dipped in aqueous product obtained by electrolysis of brine solution turns to blue colour. Because it is a basic solution.  

17. What is brine solution ? What products will obtain when this solution is subjected to electrolysis ? (May 2025)

Ans. :

★  Aqueous solution of sodium chloride is called brine solution.

★  H2 / Hydrogen gas, Cl2/ Chlorine gas and NaOH / Sodium hydroxide  

18. What is water of crystallisation ? Write the molecular formula of any two salts that contain water of crystallisation. (July 2025)

Ans. : Water of crystallisation is the fixed number of water

molecules present in one formula unit of a salt.      

19. When concentrated sulphuric acid is added to a test tube containing solid sodium chloride the gas ‘X’ will be released. What are the ions formed when this gas is passed into water? What are the products formed when the gas ‘X’ is passed into an aqueous basic solution obtained in the chlor-alkali process? (MQP-2 25-26) 

Ans: 

 ★ Ions: Hydrogen ion / H+ OR Hydronium ion / H3O+ and   Chloride ion / Cl- 

★ Products:  Sodium chloride / NaCl  and Water / H2O 

20. A solution of baking soda is commonly applied to the area of a honey bee stung area. Justify this action. (MQP-3 25-26)

Ans: 

★ Stung of honey bee contains methanoic acid which causes pain and irritation.

 ★ Applying baking soda on stung area neutralises the acid and gives relief. 

21. Analyze the list of experiments in the table given below. In which of the experiments the following salts will be produced?      (MQP - 4 25-26)

(i) An acidic salt

(ii)  A neutral salt 

Ans. : 

(i)  Experiment No. 1 

(ii)  Experiment No. 3 and 4                  

     Three Marks questions 

1. Draw the diagram of arrangement of the apparatus to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts :

i) Zinc granules ii) Soap solution. (june 2022)

 Ans. :

Reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. 

2. a) What is neutralisation reaction ? Give an example.

b) What is the common name of the compound that has molecular formula CaSO4. 1/2 H2O. (june 2022)

Ans. :

a) Reaction between acids and bases to form salt and water is called neutralisation reaction. 

OR

Base + Acid → Salt + water.

Ex : NaOH + HCl → NaCl + H2O.  [ Consider any suitable example ]

b) Calcium sulphate hemihydrate or Plaster of Paris.

3. Draw the diagram of arrangement of the apparatus to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts : (March 2022)

i) Zinc granules ii)Delivery tube.

Ans. : 

Reaction of zinc granules with dilute sulphuric acid :

4. Write the molecular formulae and two uses of each of the following compounds : a) Bleaching powder b) Plaster of Paris. (Sep 2020)

Ans. :

a)

CaOCl2

Uses

★  for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry.

★  as an oxidising agent in many chemical industries

★  to make drinking water free from germs. ( Any two uses)

b)

CaSO4. 1/2 H2O

Uses

★  for making toys

★  making materials for decoration

★  for making surfaces smooth. ( Any two uses ) 

5. What is a strong acid ? Explain how tooth decay is caused. How can it be prevented ? (Sep 2020)

Ans: 

★  Acid that gives rise to more +H ions is said to be strong acid.

★  Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. So the pH in the mouth decreases and the tooth enamel gets corroded.

★  Using toothpastes which are generally basic, for cleaning the teeth.

6. When the brine solution is subjected to electrolysis, name the compound formed and the gases released at the cathode and the anode. Write one use of each product. (July 2025)

Ans:

★  Compound formed — NaOH / Sodium hydroxide

Use : 

Degreasing metals / Soaps & detergents / Paper making / Artificial fibres.

★  Gas released at anode : Cl2 / Chlorine gas

 Use : 

As disinfectant in water purification / in swimming pools / In the manufacture of PVC / CFC / As insecticide. ( Any one )

★  Gas released at cathode : H2 /Hydrogen gas.

Use : 

as fuels / in the preparation of Margarine / in the manufacture of Ammonia for fertilizers.

7. a) What is acid rain? 

b) Which gas is liberated when an acid reacts with a metal carbonate? 

c) Write the chemical name and molecular formula of baking soda. (MQP-2 25-26)

Ans: 

a) When pH of rain water is less than 5.6, it is called acid rain. 

b) Carbon dioxide / CO2 

c) Chemical name : Sodium hydrogen carbonate / Sodium bicarbonate Molecular formula : NaHCO3 

8. a) What is neutralization? 

 b) Name the acid present in the following substances. i) Curd ii) Gastric juice (MQP - 4 25-26)

Ans.: 

a) The reaction between an acid and a base to give salt and water is known as a neutralisation reaction. 

b) 

(i) Lactic acid 

(ii) Hydrochloric acid 

9. a) What is water of crystallisation? 

b) Name the salts used in the following processes. 

(i) Removing permanent hardness of water. 

(ii) Bleaching wood pulp in paper factories. (MQP-4 25-26)

Ans:

a) Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt. 

b) 

(i) Sodium carbonate / Na2CO3 / washing soda. 

(ii) Calcium oxychloride / CaOCl2 / Bleaching powder. 

     Four Marks Questions 

1. (i) What is neutralisation reaction ? 

(ii) Name the products of chlor-alkali process. Write one use of each. (June 2019)

Ans: 

(i) Neutralization is a type of chemical reaction in which an acid reacts with a base to form salt and water.

(ii) There are three products that are produced in the Chlor-alkali process. These are Sodium Hydroxide (NaOH), chlorine gas (Cl2), and hydrogen gas(H2).

Uses of sodium hydroxide

★  It is used in the manufacturing of paper.

Uses of chlorine

★  It is used in the production of bleaching powder.

Uses of Hydrogen gas

★  It is used as fuel for rockets.

2. a) NaOH, Ca (OH)2, H2 and Cl2 materials are given to you. By using which of these materials you can prepare bleaching powder ? Write the chemical name and one use of the bleaching powder.

b) i) How do you identify a solution as basic solution by using blue litmus paper ? 

ii) Under what condition does a farmer treat the soil of his field with slaked lime ? (April 2025)

Ans: 

a) 

★  Ca (OH)2 and Cl2

★  CaOCl2 / Calcium oxychloride

 ★ 

— for bleaching cotton and linen in the textile industry

— for bleaching wood pulp in paper factories

— for bleaching washed clothes in laundry

— as an oxidising agent in many chemical industries

— as disinfectant to make drinking water free from germs.

b) 

i) The blue litmus paper does not change its colour in basic solution. 

ii) 

 ★ When acidic property of soil increases

 ★ When pH value of soil decreases

 ★ When the concentration of   H+ /H3O+ ions in soil increases. ( any one )

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