MG SCHOOL EDUCATION: Cls 10 Sci Chap 1 Previous years appeared questions

Chapter 1 Chemical Reactions And Equations

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

(D) displacement reaction

Ans: (D) displacement reaction

4. What type of chemical reaction takes place when electricity is passed through water? (KREIS Midterm-22)

A) Combination B) Displacement

C) Decomposition D) Double Displacement

Ans: C) Decomposition

6. The reaction in which two compounds exchange their ions to form two new compounds. (KREIS Mid Term-22)

a) redox reaction

b) double displacement reaction

c) combination reaction

d) displacement reaction

Ans: b) double displacement reaction

7. 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) Al2O 3 and HCl (C) NaOH and H2SO4 (D) Na2O and CO2 Ans. : (A) BaCl2 and Na2SO4

8. 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

9. 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

Ans: (B) chemical combination

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

(A) decomposes into simpler products

(B) loses water molecules

(D) produces brown fumes

Ans. : (B) loses water molecule

11. 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

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

One Marks 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)

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.

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. :

Electrolysis of water :

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.

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. Identify the substance that are oxidized and the substance that are reduced in the following reactions.

i. 4Na(s) + O2(g) → 2Na2O(s)

ii. CuO(s) + H2(g) → Cu(s) + H2O(l) (KREIS Midterm 2022)

Ans:

i. Oxidized substance - Na

Reduced substance - O2

ii. Oxidized substance - H2

Reduced substance - CuO

7. What are the methods of preventing Rancidity? (KREIS Midterm 2022)

Ans:

> Adding antioxidants to food.

> Keeping food in refrigerator.

> Storing food in airtight containers.

> Packaging food and oil in Nitrogen Gas.

8.How exothermic reaction is differ from endothermic reaction? Give an example each. (KREIS Mid Term-22)

Ans:

Exothermic reaction is a reaction in which energy is released in the form of light or heat.

ex: CaO + H2O → Ca(OH)2 + Heat

Endothermic reactions is al reactions in which the reactants absorb heat energy from the surroundings to form products.

Heat

Ex: CaCO3 → CaO + CO2

9. In the given reaction, name the following. 4Na(s) +O2(g) → 2Na2O (s)

a) oxidizing substance b) reducing substance (KREIS Mid Term-22)

Ans:

a) oxidizing substance: Na

b) reducing substance: O2

10. 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

11. “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

12. 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) BaSO 4 / barium sulphate

ii) SO 2 − 4 — sulphate radical, Ba 2 + — Barium ion

iii) Double displacement reaction / precipitation reaction.

Three Marks Questions

1. Write the balanced chemical equation for the following chemical reactions : (March 2022)

i) Calcium carbonate --Heat--> Calcium oxide + Carbon dioxide

ii) Hydrogen + Chlorine → Hydrogen chloride

iii) Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen.

Ans:

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) 32. 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:

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:

Heat

2FeSO4(s) → Fe2O3(s)+SO2(g)+SO3(g)

> It is an endothermic reaction

ii)

CaO+H2O→Ca(OH)2 + Heat

> It is exothermic reaction

8. In the electrolysis of water

a. Name the gas collected at anode and cathode.

b. Why the volume collected at one electrode is more than the other?

c. How will you test the liberated gas? (KREIS Midterm 2022)

Ans:

a) The gas collected at cathode is hydrogen and the gas collected at anode is oxygen.

b) This is because water contains two parts of hydrogen element as compared to one part of oxygen element by volume.

c) When a matchstick is brought near the gases evolved, hydrogen gas burns with a pop sound while oxygen gas being a supporter of gas make the matchstick burn brightly.

9. Write the balanced chemical equation for the following reactions.

a) Lime stone on heating

b) Burning of natural gas

c) Zinc reacts with copper sulphate solution. (KREIS Mid Term -22)

Ans:

Heat

a) CaCO3(s) → CaO(s) + CO2(g)

b) CH4(g) + 2O2(g) → 2H2O(g) + CO2(g)

c) Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)

10. Write the balanced chemical equation for the following reactions.

a) Zinc carbonate (s) → Zinc oxide (s)+ Carbon dioxidHeat)

b) Magnesium(s) + Hydrochloric acid (aq) →Magnesium chloride (aq) + Hydrogen (g)

c) Calcium oxide (s)+ Water → Calcium hydroxide (aq) + Heat (KREIS Mid Term -22)

Ans:

a) ZnCO3(s) → ZnO(s) + CO2(g)

b) Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

c) CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat

11. 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.

The above reaction is an endothermic or decomposition reaction.

11. 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.

★ Substances which prevent oxidation (antioxidants) are added to food.

★ Keeping food in airtight containers

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 ? (KSEEB MQP 2024)

i) Barium chloride reacted with sodium sulphate.

ii) Zinc reacted with hydrochloric acid.

Ans:

★ Insoluble precipitate will be formed in chemical reaction one.

★ 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.

IMPORTANT QUESTIONS

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

Ans:

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

★ 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 those are more reactive than hydrogen displaces it from the dilute acids

Example : Sodium , Potassium , Zinc , Iron

Metals those are less reactive than hydrogen does not displaces it from the 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 they form alkalis which are basic in nature

Ex : 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 do 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 9. What is ionic bond ?

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 outer most orbit.

★ To attain octave configuration sodium donates one electron to chlorine atom, then it will becomes positive ion

★ As chlorine atom receive one electron from sodium, it becomes negative ion

★ Hence there is a strong electrostatic force of attraction between Na+ and Cl- ions results in the formation of ionic bond between sodium and chlorine.

9. Why do Aluminium oxide is 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 an 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 elements like metals i.e can loose electrons to form positive ions.

12. 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

13. 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 result of chemical reaction and gets deposited on the surface of metal. It forms a protective coating on the surface and prevents the attacks of water, air, acids or alkalis.

14. 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

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