MG SCHOOL SCIENCE

 Chapter 1: Chemical Reactions and Equations

MG SCHOOL SCIENCE - Class 10 Science Chapter 1 Previous Years Appeared Questions

Multiple Choice Questions

1. The metal that displaces copper from copper sulphate solution is  (June 2022)

(A) mercury  

(B) gold  

(C) iron  

(D) silver

Ans. : (C) iron

2. The gas liberated at the cathode in the electrolysis of water is  (March 2022)

(A) Oxygen  

(B) Hydrogen  

(C) Chlorine  

(D) Nitrogen.

Ans. : (B) Hydrogen

3. Fe2O3 + 2 Al → Al2O3 + 2 Fe
The type of above chemical reaction is  (June 2019)

(A) combination reaction  

(B) double displacement reaction  

(C) decomposition reaction  

(D) displacement reaction

Ans. : (D) displacement reaction

4. The reactants that exchange ions by reacting with each other and form a precipitate among the following are  (April 2023)

(A) BaCl2 and Na2SO4  

(B) Al2O3 and HCl  

(C) NaOH and H2SO4  

(D) Na2O and CO2

Ans. : (A) BaCl2 and Na2SO4

5. Chips manufacturers, flush bags of chips with nitrogen gas because, to  (June 2023)

(A) prevent corrosion of chips  

(B) prevent chips from getting oxidised  

(C) make chips undergo rancidity  

(D) prevent the chips from getting reduced.

Ans. : (B) prevent chips from getting oxidised

6. A type of chemical reaction in which a single product is formed by two or more reactants is  (KSEEB MQP 2024)

(A) chemical decomposition  

(B) chemical combination  

(C) chemical displacement  

(D) chemical double displacement

Ans. : (B) chemical combination

7. Ferrous sulphate crystals lose green colour when heated. Because this compound  (April 2024)

(A) decomposes into simpler products  

(B) loses water molecules  

(C) releases sulphur dioxide gas  

(D) produces brown fumes

Ans. : (B) loses water molecule

8. In the electrolysis of water the gases that are released at cathode and anode and their ratio respectively are,  (August 2024)

(A) Hydrogen:Oxygen ; 1:2  

(B) Oxygen:Hydrogen ; 2:1  

(C) Hydrogen : Oxygen ; 2:1  

(D) Oxygen : Hydrogen ; 1:2

Ans. : (C) Hydrogen : Oxygen ; 2:1

9. The electrolysis of water to form hydrogen and oxygen gases is  (MQP 2025)

(A) an endothermic reaction  

(B) a displacement reaction  

(C) an exothermic reaction  

(D) a redox reaction

Ans. : (A) an endothermic reaction

10. The reactants that exchange ions by reacting each other and form a precipitate among the following are  (MQP 2025)

(A) Aluminium oxide and hydrochloric acid  

(B) Sodium hydroxide and sulphuric acid  

(C) Aluminium oxide and hydrochloric acid  

(D) Barium chloride and sodium sulphate

Ans. : (D) Barium chloride and sodium sulphate

11. ZnO + C → Zn + CO ; the reactants that are oxidised and reduced in this chemical reaction respectively are  (MQP 2025)

(A) ZnO and C  

(B) C and ZnO  

(C) Zn and CO  

(D) Co and Zn

Ans. : (B) C and ZnO

12. 2AgCl → 2Ag + Cl2; the type of this chemical reaction is  (SLP - 2025)

(A) Combination reaction  

(B) Displacement reaction  

(C) Decomposition reaction  

(D) Double displacement reaction

Ans. : (C) Decomposition reaction

13. The gas flushed to the bags containing chips is  (May - 2025)

(A) Hydrogen  

(B) Oxygen  

(C) Chlorine  

(D) Nitrogen

Ans. : (D) Nitrogen

14. In this chemical reaction, CuO + H2 → Cu + H2O  (April 2025)

(A) hydrogen is reduced to form water  

(B) exchange of ions took place between the reactants  

(C) copper oxide is oxidised to form copper  

(D) copper oxide is reduced to form copper

Ans. : (D) copper oxide is reduced to form copper

15. Zn + CuSO4 → ZnSO4 + Cu
The above reaction is an example for  (July 2025)

(A) Endothermic reaction  

(B) Precipitation reaction  

(C) Displacement reaction  

(D) Double displacement reaction

Ans. : (C) Displacement reaction

16. Analyse the experiment expressed in the figure. The molecular formulae of the solution 'Y' that gives a yellow colour precipitate by reacting with KI solution and the another product that forms here respectively are  (KSEEB MQP - 1 25-26)

(A) Pb(NO3)2 and KNO3  

(B) PbI2 and KNO3  

(C) Pb(NO3)2 and KI  

(D) Pb(NO3)2 and K2SO4

Ans. : (B) PbI2 and KNO3

17. Silver chloride turns grey when exposed to sunlight. This is because silver chloride  (MQP - 2 2025-26)

(A) decomposes to form silver.  

(B) decomposes to form chlorine.  

(C) combines with oxygen.  

(D) reacts with atmospheric moisture.

Ans. : (A) decomposes to form silver.

18. Observe the following chemical equations. Identify the correct statement
CuSO4 + Fe → FeSO4 + Cu
2AgNO3 + Cu → Cu(NO3)2 + 2Ag  (MQP-3 2025-26)

(A) Copper is more reactive than iron and silver
(B) Iron is less reactive than copper and silver

(C) Copper is more reactive than silver but less reactive than iron

(D) Silver is more reactive than copper and iron.

Ans. : (C) Copper is more reactive than silver but less reactive than iron

19. An example for the chemical change among the following is  (May 2026)

(A) Dissolving of salt in water  

(B) Tearing of paper  

(C) Rusting of iron  

(D) Boiling of water

Ans. : (C) Rusting of iron

One Mark Questions

1. ZnO + C → Zn + CO
In this reaction name the reactant i) that is oxidised and ii) that is reduced.  (March 2022, April 2024)

Ans. : Oxidised reactant is : C
Reduced reactant is : ZnO.

2. Manufacturers of chips, flush the packets of chips with nitrogen gas. Why?  (Sep 2020)

Ans. : To prevent the chips from getting oxidised. OR To prevent rancidity.

3. CuO + H2 → Cu + H2O
In this reaction name the reactant i) that is oxidised ii) that is reduced.  (March 2020, May - 2025)

Ans. : i) Hydrogen or H2
ii) Copper Oxide or CuO.

4. Oil and fat containing food items are flushed with nitrogen. Why?

Ans. : Nitrogen is an inert gas, hence it acts as antioxidant and prevents the oils and fats from oxidation.

5. Packets of chips are flushed with nitrogen gas. Why?  (April 2023)

Ans. : To prevent chips from getting oxidised / to prevent rancidity.

6. An iron nail is dropped into a test tube having copper sulphate solution. The iron nail gradually turns to brownish colour. Why?  (April 2023)

Ans. : Since iron is more reactive than copper, it displaces copper from copper sulphate solution / Displaced copper gets deposited on the iron nail.

7. Name the product produced when calcium oxide reacts with water.  (April 2023)

Ans. : Calcium hydroxide

8. What are redox reactions ?  (August 2024)

Ans. : A chemical reaction in which one reactant gets oxidised while the other gets reduced is called redox reaction.

9. How can rancidity be controlled?

Ans. : • Adding antioxidants to food.
• Keeping food in refrigerator.
• Storing food in airtight containers.
• Packaging food and oil in Nitrogen Gas.

10. How is rancidity prevented in foods containing fat or oil ?  (July 2025)

Ans. : • Adding antioxidants
• Storing in airtight containers
• Flushing gases like nitrogen into the packets containing fried foods. (Any two)

11. Which ions produce a white precipitate when the solution of sodium sulphate is added to the solution of barium chloride?  (April 2025)

Ans. : Ba2+ and SO42-

12. What is the reason for the formation of brown coloured fume in the experiment shown through lead nitrate decomposition?  (MQP-3 2025-26)

Ans. : Due to the evolution of nitrogen dioxide gas by the decomposition of lead nitrate

13. What is rancidity?  (MQP-4 2025-26)

Ans. : The process by which fat and oil substances are oxidized, changing their smell and taste, is called rancidity.

14. Observe the given equation. Which numbers respectively will be in the positions W, X, Y and Z when this equation is balanced ?  (March 2026)

Ans. : 2, 2, 4, 1.

Two Marks Questions

1. Draw the diagram of the arrangement of apparatus used to show the electrolysis of water and label the 'graphite rod'.  (June 2022, March 2019, KSEEB MQP 2021)

Ans. : [Diagram / Activity Question: Electrolysis of water arrangement with labelled cathode, anode, graphite rod, test tubes, and water filled vessel.]

2. The chemical reaction that takes place between sodium sulphate and barium chloride is called double displacement reaction. Why ? Write the balanced chemical equation for this reaction.  (June 2022)

Ans. : • There is an exchange of ions between the reactants sodium sulphate and barium chloride.
• Na2SO4 + BaCl2 → BaSO4 + 2NaCl

3. What is the type of chemical reaction in which quicklime is obtained by lime stone (calcium carbonate)? Write a chemical equation for this reaction.  (March 2022)

Ans. : • Decomposition reaction or thermal decomposition reaction / endothermic reaction.
• CaCO3 --Heat--> CaO + CO2

4. Write the balanced chemical equation for the following reactions :
(i) Hydrogen + Chlorine → Hydrogen chloride
(ii) Sodium + Water → Sodium hydroxide + Hydrogen.  (June 2019)

Ans. : (i) H2 + Cl2 → 2HCl
(ii) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

5. Name the brown fumes liberated when lead nitrate is heated. Write the balanced chemical equation for this reaction.  (March 2019)

Ans. : • The brown fume coming out when lead nitrate is heated is due to the liberation of Nitrogen dioxide gas.
• 2Pb(NO3)2 → 2PbO + 4NO2 + O2

6. Calcium oxide reacts with water to form slaked lime. What type of Chemical reaction is this? Write the balanced chemical equation for this reaction.  (KSEEB Model paper 22-23)

Ans. : • Combination Reaction / Exothermic reaction
• CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat

7. “Calcium oxide and carbon dioxide are produced on heating calcium carbonate.” Write the balanced chemical equation for this reaction. Mention the type of this chemical reaction.  (April 2023)

Ans. : • CaCO3 → CaO + CO2
• (Thermal) decomposition reaction / endothermic reaction

8. Add same amount of barium chloride solution to a test tube containing 5 ml of sodium sulphate solution. Then
i) Which insoluble white precipitate is formed ?
ii) Name the ions responsible for the formation of white precipitate.
iii) Mention the type of chemical reaction that took place here.  (June 2023)

Ans. : i) BaSO4 / barium sulphate
ii) SO42- → sulphate radical, Ba2+ → Barium ion
iii) Double displacement reaction / precipitation reaction.

9. Observe the test tubes A, B and C given in the following figures.
i) In which test tube the iron nail undergoes rust ? Why ?
ii) Iron nails present in other two test tubes do not rust. Why ?  (May - 2025)

Ans. : i) Iron nail present in test tube A. Both moisture and air available.
ii) In test tube B only moisture is available but not oxygen. In test tube C only air is available but not moisture.

10. What is rancidity ? Mention any two methods of preventing rancidity.  (April 2025)

Ans. : When fat and oil containing food materials oxidise, then their smell and taste change. This is called rancidity.
Methods of preventing rancidity :
• Adding antioxidants
• Keeping fried food materials in airtight containers
• Flushing bags of chips with nitrogen gas.

11. Translate the following statement into chemical equation and then balance it.
'Hydrogen gas combines with chlorine gas to form hydrogen chloride.'  (July 2025)

Ans. : H2 + Cl2 → 2HCl

Three Marks Questions

1. Write the balanced chemical equation for the following chemical reactions :
i) Calcium carbonate --Heat--> Calcium oxide + Carbon dioxide
ii) Hydrogen + Chlorine → Hydrogen chloride
iii) Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen.  (March 2022)

Ans. : i) CaCO3 --Heat--> CaO + CO2
ii) H2 + Cl2 → 2HCl
iii) Mg + 2HCl → MgCl2 + H2

2. Which type of chemical reaction takes place when an iron nail is dipped in copper sulphate solution ? Why ? Write a balanced chemical equation for this chemical reaction.  (March 2022)

Ans. : • Chemical displacement reaction.
• Because more reactive iron displaces copper from copper sulphate solution.
• Fe + CuSO4 → FeSO4 + Cu.

3. Write the balanced chemical equations for the following chemical reactions. How can we confirm by observation that these chemical reactions are taking place ?
a) Lead nitrate is heated.
b) Sodium sulphate reacts with Barium chloride.  (Sep 2020)

Ans. : a) 2Pb(NO3)2 → 2PbO + 4NO2 + O2
By the formation of brown coloured fumes.

b) Na2SO4 + BaCl2 → BaSO4 + 2NaCl
By the formation of white coloured precipitate.

4. The reaction of Barium chloride with Aluminium sulphate solution is an example for which type of chemical reaction ? Why ? Write the balanced chemical equation for this reaction.  (March 2020)

Ans. : • It is an example for double displacement reaction / Precipitation reaction.
• There is an exchange of ions between the reactants / White precipitate of Barium Sulphate is formed.
• BaCl2 + Al2(SO4)3 → 3BaSO4 + 2AlCl3.

5. Draw the diagram of the apparatus used in electrolysis of water. Label the following parts : (i) Cathode (ii) Graphite rod.  (June 2019)

Ans. : [Diagram / Activity Question: Electrolysis of water apparatus diagram showing cathode, anode, graphite rod, and gas collection.]

6. The reaction of lead with Copper Chloride solution is an example for which type of chemical reaction? Why? Write the balanced chemical equation for this reaction.  (KSEEB MQP 2021)

Ans. : • Chemical displacement reaction.
• Because more reactive lead displaces copper from copper Chloride solution.
• Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s)

7. Write the balanced chemical equations for the following reactions and identify the exothermic and endothermic reaction.
i) heating of ferrous sulphate crystals.
ii) calcium oxide reacts with water.  (KSEEB MQP 2021)

Ans. : i) 2FeSO4(s) --Heat--> Fe2O3(s) + SO2(g) + SO3(g)
  It is an endothermic reaction.
ii) CaO + H2O → Ca(OH)2 + Heat
  It is an exothermic reaction.

8. Silver chloride exposed to the sunlight turns grey colour. Why? Write the balanced chemical equation for this reaction and mention the type of reaction.  (KSEEB Model paper 22-23)

Ans. : White silver chloride turns grey in sunlight due to the decomposition of silver chloride into silver and chlorine by light.
Equation: 2AgCl --Sunlight--> 2Ag + Cl2
The above reaction is an endothermic or decomposition reaction.

9. a) Identify the substances that are oxidised and reduced in the following chemical reaction:
ZnO + C → Zn + CO
b) What is rancidity ? Mention any two methods to prevent rancidity.  (April 2024)

Ans. : a) ZnO is reduced. C is oxidised.
b) When fats and oils are oxidised, they become rancid and their smell and taste change.
Methods to prevent rancidity:
• Substances which prevent oxidation (antioxidants) are added to food.
• Keeping food in airtight containers.

10. Mention any two factors that help to determine that a change is a chemical reaction.
Mention the type of chemical reaction that takes place when sodium sulphate solution is added to barium chloride solution. Write the balanced chemical equation for this reaction.  (June 2025)

Ans. : a) Factors to determine chemical reaction:
• Formation of new substances
• Change in colour
• Change in state
• Change in temperature
• Evolution of a gas

b) Double displacement reaction.
Equation: BaCl2 + Na2SO4 → BaSO4 + 2NaCl

11. Write the chemical equations for the following reactions:
i) Quicklime is reacted with water
ii) Zinc pieces are added to copper sulphate solution
iii) Sodium chloride solution is added to silver nitrate solution.  (April 2025)

Ans. : i) CaO + H2O → Ca(OH)2 + Heat
ii) Zn + CuSO4 → ZnSO4 + Cu
iii) NaCl + AgNO3 → NaNO3 + AgCl

12. In which of the following chemical reactions water insoluble precipitate will be formed ? Explain. Which water soluble products are formed in both of the reactions ?
i) Barium chloride reacted with sodium sulphate.
ii) Zinc reacted with hydrochloric acid.  (KSEEB MQP 2024)

Ans. : • Insoluble precipitate will be formed in chemical reaction (i).
• Sodium sulphate and barium chloride react to produce water insoluble white precipitate of barium sulphate.
• Water soluble product formed in reaction (i) is sodium chloride and in reaction (ii) zinc chloride.

13. Write the balanced chemical equations for the following word equations.
(i) Manganese oxide + hydrochloric acid → manganese chloride + chlorine + water
(ii) Calcium hydroxide + carbon dioxide → calcium carbonate + water
(iii) Zinc carbonate → zinc oxide + Carbon dioxide  (KSEEB MQP - 1 25-26)

Ans. : (i) MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(ii) Ca(OH)2 + CO2 → CaCO3 + H2O
(iii) ZnCO3 → ZnO + CO2

14. Convert the following chemical reactions into chemical equations.
(i) Ammonia forms when nitrogen gas reacts with hydrogen gas.
(ii) Sodium oxide reacts with water to form sodium hydroxide.
(iii) By reacting with water potassium metal produces potassium hydroxide and hydrogen gas.  (KSEEB MQP-1 25-26)

Ans. : (i) 3H2 + N2 → 2NH3
(ii) Na2O + H2O → 2NaOH
(iii) 2K + 2H2O → 2KOH + H2

15. Balance the following equations
(i) Mg + N2 → Mg3N2
(ii) NaOH + H2SO4 → Na2SO4 + H2O
(iii) Al(OH)3 → Al2O3 + H2O  (MQP-2 2025-26)

Ans. : (i) 3Mg + N2 → Mg3N2
(ii) 2NaOH + H2SO4 → Na2SO4 + 2H2O
(iii) 2Al(OH)3 → Al2O3 + 3H2O

16. Convert the following chemical reactions into chemical equations.
(i) Copper reacts with concentrated nitric acid.
(ii) Silver nitrate solution is added to potassium bromide solution.
(iii) Zinc oxide is reduced by coke.  (MQP-2 2025-26)

Ans. : (i) Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
(ii) KBr + AgNO3 → KNO3 + AgBr
(iii) ZnO + C → Zn + CO

17. a) Magnesium ribbon burns with a dazzling white flame in the air and change into magnesium oxide. Mention the type of reactions.
b) List out the observations that help us to determine that a chemical reaction has taken place.  (MQP-3 2025-26)

Ans. : a) Chemical combination reaction.
b) Observations:
• Change in colour
• Evolution of a gas
• Change in temperature
• Change in state

18. Write the balanced chemical equations for the following reactions.
a) Calcium carbonate → Calcium oxide + carbon dioxide
b) Hydrogen + chlorine → Hydrogen chloride
c) Magnesium + hydrochloric acid → Magnesium chloride + Hydrogen  (MQP-4 25-26)

Ans. : a) CaCO3 → CaO + CO2
b) H2 + Cl2 → 2HCl
c) Mg + 2HCl → MgCl2 + H2

19. a) Chemical equations have to be balanced. Why?
b) Mention the measures that are followed to prevent rusting of iron.  (MQP-3 25-26)

Ans. : a) According to the law of conservation of mass, the number of atoms of each element remains the same before and after chemical reaction.
b) Measures to prevent rusting:
• Oiling
• Greasing
• Painting
• Galvanisation
• Chrome plating
• Anodisation

20. Observe the solutions of compounds given below and answer the following questions: Pb(NO3)2, BaCl2, Na2SO4, KI.
a) Which solutions are to be reacted with each other to get white precipitate? Mention the type of this reaction.
b) Which positive and negative ions combine to form this precipitate ?  (March - 2026)

Ans. : a) Na2SO4 and BaCl2. Chemical double displacement / Precipitation reaction
b) Ba2+ and SO42-.

Important Questions

1. Show the formation of Na2O and MgO by the transfer of electrons.

Ans. : [Electron Transfer Diagram / Explanation for formation of Na2O and MgO from Na+, Mg2+, and O2- ions.]

2. What are the general properties for ionic compounds

Ans. : • Ionic compounds are solids and are somewhat hard
• Ionic compounds have high melting and boiling points
• Ionic compounds are generally soluble in water and insoluble in organic solvents
• Ionic compounds conduct electricity in the molten state

3. Name any two metals those displaces hydrogen from the dilute acids and two metals those does not displaces hydrogen from the dilute acids.

Ans. : • Metals that are more reactive than hydrogen displace it from dilute acids. Example : Sodium, Potassium, Zinc, Iron
• Metals that are less reactive than hydrogen do not displace it from dilute acids. Example : Copper, Silver

4. Give reasons -
(a) Platinum, Gold, Silver are used in making ornaments
(b) Sodium, Potassium are stored in kerosene
(c) Aluminium is used in utensils even it is more reactive.

Ans. : a) Shining surface / Metallic lustre, Ductility and Malleability, Less reactivity
b) These metals are highly reactive with air and water. So they are kept in kerosene.
c) Aluminium is lighter and good conductor. Aluminium forms oxide layer to prevent itself from further corrosion.

5. Why the metal oxides are said to be basic oxides. Explain with an example.

Ans. : Metal oxides when dissolved in water form alkalis which are basic in nature.
Example : Sodium hydroxide is formed on dissolving sodium oxide in water:
Na2O + H2O → 2NaOH

6. You are given cold water and hot water in two separate test tubes. If you kept a piece of magnesium in test tube containing cold water it shrinks, while in hot water it floats. Give reason

Ans. : • Magnesium does not react with cold water.
• Magnesium liberates hydrogen gas when it reacts with hot water.
• It also starts floating due to the bubbles of hydrogen gas sticking to its surface.

7. Define ductility and malleability.

Ans. : • The ability of metals to be drawn into thin wires is called ductility.
• Some metals can be beaten into thin sheets. This property is called malleability.

8. Explain the formation of ionic bond taking sodium chloride as an example.

Ans. : • A strong electrostatic force of attraction between positive and negative ions is called ionic bond.
• Sodium has an atomic number 11, its electron configuration is 2, 8, 1.
• Chlorine has an atomic number 17, its electron configuration is 2, 8, 7.
• So, sodium has 1 and chlorine has 7 electrons in their outermost orbit.
• To attain octet configuration sodium donates one electron to chlorine atom, becoming a positive ion (Na+).
• As chlorine atom receives one electron from sodium, it becomes a negative ion (Cl-).
• Hence there is a strong electrostatic force of attraction between Na+ and Cl- ions resulting in the formation of ionic bond between sodium and chlorine.

9. Why is Aluminium oxide called amphoteric oxide? Explain with help of chemical equations.

Ans. : Aluminium oxide (Al2O3) reacts with both acids as well as bases to produce salt and water, hence it is called as amphoteric oxide.

• Aluminium oxide reacts with acid:
  Al2O3 + 6HCl → 2AlCl3 + 3H2O
• Aluminium oxide reacts with base:
  Al2O3 + 2NaOH → 2NaAlO2 + H2O

10. Metals are arranged in the reactivity series. Why hydrogen is kept in the series though it is not a metal?

Ans. : Hydrogen is a non-metal but still it is placed in the reactivity series because it behaves as an electropositive element like metals i.e., can lose electrons to form positive ions.

11. You are provided with three metals: sodium, magnesium and copper. Using only water as the reactant, how will you identify each of them?

Ans. : (a) The metal which reacts violently with cold water and catches fire is sodium.
(b) The metal which evolves hydrogen gas upon heating with water is magnesium.
(c) The metal which does not react with water even on strong heating is copper.

12. Corrosion of metals is not always harmful. Illustrate.

Ans. : Corrosion is a very harmful process resulting in slow eating up of a metal, but corrosion of aluminium is useful as a layer of aluminium oxide (Al2O3) formed as a result of chemical reaction gets deposited on the surface of metal. It forms a protective coating on the surface and prevents attacks of water, air, acids or alkalis.

13. Classify the following oxides as acidic, basic and amphoteric oxides: ZnO, MgO, SO2, CO2, Na2O, CaO, Al2O3.

Ans. : Acidic oxides : SO2, CO2
Basic oxides : MgO, Na2O, CaO
Amphoteric oxides : ZnO, Al2O3