NIOS Class 10 Science and Technology Chapter 4 Questions Answers

This chapter is from Module 2 Matter in Our Surroundings. This post provides you complete answer of all intext and terminal questions given in Chapter 4.

Our experienced teachers have provided easy and accurate answers to all questions that will help you complete your assignments.

CHEMICAL REACTION AND EQUATIONS-Overview

In this lesson on chemical reactions and equations form NIOS class 10 Science, students will gain a basic understanding of how chemical change occur and they will able to write and balance chemical equations. This lesson also classifies chemical reactions into different types.

Intext Questions 4.1 with Answers

Q1. Write a chemical equation for each of the following reactions:

(i)     Zinc metal reacts with aqueous hydrochloric acid produce a solution of zinc chloride and hydrogen gas.

(ii)    When solid mercury (II) oxide is heated, liquid mercury and oxygen gas are produced

Answer

(i)          Zn + 2HCl  ZnCl₂ + H₂

(ii)       

Q2. Balance the following chemical equations:

(i)         H₂SO_4(aq) + NaOH_(aq) → Na₂SO_4(aq)  + H₂O_(l)

(ii)      Al_(s) + HCl_(aq) → AlCl₃ + H_2(g)

Answer

(i)     H₂SO_4(aq) + 2NaOH_(aq) → Na₂SO_4(aq)  + 2H₂O_(l)

(ii)   2Al_(s) + 6HCl_(aq)   →  2AlCl₃+ 3H_2(g)

 

Q3. What is a balanced chemical equation? Why should a chemical equation be balanced?

Answer

 The chemical equation in which the number of atoms of each element on both reactant and product sides is the same, is called a balanced chemical equation.

A chemical equation should be balanced because it follows the ‘Law of conservation of mass’. According to this law- mass can neither be created nor be destroyed in a chemical reaction.

Intext Questions 4.2 with Answers

Q1. Examine the following reaction(s) and identify which of them are not example(s) of a redox reactions?

(i)    AgNO_3(aq)  + HCl →AgCl + HNO_3(aq)

(ii)    MnO_2(s)   + 4HCl_(aq)→ MnCl_2(aq) +2H₂O_(l) +Cl_2(g)

(iii)   4Na_(s)  +O_2(g)→2Na₂O_(s)

Answer

(i)     AgNO_3(aq)  + HCl →AgCl + HNO_3(aq)

This a double displacement reaction and there is no change in oxidation states of any element, so this is not a redox reaction.

(ii)   MnO_2(s)   + 4HCl_(aq)→ MnCl_2(aq) +2H₂O_(l) +Cl_2(g)

In this reaction Mn changes from +4 (in MnO₂) to +2 (MnCl₂) so it is reduced.

Cl changes from -1 (in HCl) to 0 (in Cl₂) so it is oxidised.

That’s why this is a redox reaction.

(iii)    4Na_(s)  +O_2(g)→2Na₂O_(s)

In this reaction, Na changes from 0  to +1, so it is oxidised.

O changes from 0 to -1, so it is reduced.

That’s why it is a redox reaction.

Q2. Identify the substances which are oxidized and the substances that are reduced in the following reactions:

(i)       H_2(g)  + Cl_2(g) 2HCl_(g)

(ii)   H_2(g) + CuO_(s) → Cu_(s)  + H₂O_(l)

(iii)     Zn_(s)  +2AgNO_3(aq) →Zn(NO₃)_2(aq) + 2Ag_(s)

Answer

(i)    Hydrogen is oxidised (oxidation state goes from 0 to  +1 in HCl)

 Chlorine is reduced (oxidation state goes from 0 to -1 in HCl)

(ii)     Hydrogen is oxidised (0 to +1 in H₂O)

    Cuo is reduced to Cu (from +2 to 0 in Cu)

(iii)      Zn is oxidised (from 0 to +2 in Zn(NO₃)₂)

                Ag is reduced (from +1 to 0 in Ag)

 

Terminal Exercise Questions with Answers

Q1. (A) Write chemical equations of the following and balance them:

(a)       Carbon + oxygen →Carbon dioxide

(b)      Hydrogen + chlorine →Hydrogen chloride

(c)       Barium chloride + Sodium sulphate →Barium Sulate + Sodium chloride

Answer

(A)   (a) C + O₂ →  CO₂

               (b) H₂  + Cl₂  →2HCl

             (c) BaCl₂ Na₂SO₄  → BaSO₄   + 2NaCl

 

 

Q1.(B) Write balanced chemical equations with physical state symbols and necessary conditions, if any:

 (a) Nitrogen reacts with hydrogen in the presence of iron as a catalyst at 200 atmospheric pressure and 600ºC temperature, and the product obtained is ammonia.

(b) Aqueous solution of sodium hydroxide reacts with hydrochloric acid and produces sodium chloride andwater.

(c ) Phosphorus burns in chlorine gas to form phosphorus pentachloride.

Answer

(B) (a) N_2(g) + 3H_2(g)  →2NH_3(g)

       (b) NaOH_(aq) + HCl_(aq) →NaCl_(s) + H₂O_(l)

              (c )  2P_(s) + 5Cl_2(g)  →2PCl_5(s)

Q1.( C ) Balance the following chemical reaction

(a)       Ca(OH)₂   + HNO₃  → Ca(NO₃)₂   +H₂O

(b)      BaCl_2(aq)  + H₂SO_4(aq)  →BaSO_4(s) + HCl_(aq)

(c)       CuSO_4(aq) + Zn_(s) →ZnSO_4(aq)  + Cu_(s)

(d)      H₂S_(g)  + SO_2(g) →S_(s)  + H₂O_(l)

(e)       BaCl_2(aq) + Al₂(SO₄)_3(aq) →AlCl_3(aq)  + BaSO_4(s)

(f)        Pb(NO₃)_2(aq) + Fe₂(SO₄)_3(aq) →Fe(NO₃)_3(aq) + PbSO_4(s)

(g)      Calcium hydroxide + carbon dioxide →Calcium carbonate + water

(h)      Aluminium + copper(II) chloride →Aluminium chloride + copper

(i)         Calcium carbonate + hydrochloric acid →Calcium chloride + water +  carbon dioxide

Answer

(a)       Ca(OH)₂   + 2HNO₃  → Ca(NO₃)₂   +2H₂O

(b)      BaCl_2(aq)  + H₂SO_4(aq)  →BaSO_4(s) + 2HCl_(aq)

(c)       CuSO_4(aq) + Zn_(s) →ZnSO_4(aq)  + Cu_(s)

(d)      2H₂S_(g)  + SO_2(g) → 3S_(s)  + 2H₂O_(l)

(e)       3BaCl_2(aq) + Al₂(SO₄)_3(aq) →2AlCl_3(aq)  + 3BaSO_4(s)

(f)      3Pb(NO₃)_2(aq) + Fe₂(SO₄)_3(aq) →2Fe(NO₃)_3(aq) + 3PbSO_4(s)

(g)       Ca(OH)₂ + CO₂  →CaCO₃ + H₂O

(h)      2Al + 3CuCl₂  →2Al + 3Cu

(i)         CaCO₃ + 2HCl →CaCl₂ + H₂O + CO₂

Q2. What is a balanced chemical equation? Write 3 characteristics of a balanced chemical equation?

Answer

 A balanced chemical equation is a chemical equation in which the number of atoms of each element is same on both reactant and product sides.

Characteristics of a Balanced Chemical Equation

    1. The number of atoms of each element is equal on both reactant and product side.

   2. Total mass of reactant is equal to the total mass of products.

   3. The correct chemical formulas and symbols of reactants and products are used and physical states are also included.

Q3. In what way is a displacement reaction different from a double displacement reaction? Explain with two suitable examples.

Answer

A displacement reaction involves the replacement of one element from a compound by the more reactive element.

In a double displacement reaction, there is mutual exchange of ions between two compounds.

Examples

(a)       Zn_(s) + CuSO_4(aq) →ZnSO_4(aq) + Cu_(s)

Zinc is more reactive  than copper so it displaces copper from copper sulphate solution. It is a displacement reaction.

(b)      BaCl_2(aq)  + Na₂SO_4(aq) → BaSO_4(s) + 2NaCl_(aq)

Barium and sodium ions exchange their places and form two new compounds. This is a double displacement reaction.

Q4. What happens when dilute hydrochloride acid is added to  iron filings? Mark(√) at the correct answer from the following:

(a)       Hydrogen gas and iron chloride are produced and is classified as a displacement reaction.

(b)      Iron chloride and chlorine gas are produced alnd is classified as a decomposition reaction.

(c)       Iron hydroxide and water are produced and is classified a combination reaction.

(d)      No reaction is takes place but is classified as a double displacement reaction.

Answer

(a)       Hydrogen gas and iron chloride are produced and is classified as a displacement reaction.

Explanation:

When iron filings are added to dilute hydrochloric acid, a displacement reaction occurs where iron displaces hydrogen from hydrochloric acid.

 Fe + 2HCl →FeCl₂ + H₂

 

Q5. What do you mean by an exothermic reaction. Give a suitable example.

Answer

The chemical reaction in which heat is released along with the products, is called an exothermic reaction.

C_(s)+ O_2(g) CO₂ + heat

Q6.Classify each of the following reactions as combination, decomposition,displacement, double displacement reactions:

(a)       Zn + 2AgNO₃   → Zn(NO₃)₂   + 2Ag

(b)     

(c)       Ni(NO₃)₂  + 2NaOH_(aq) →Ni(OH)₂  + 2NaNO_3(aq)

(d)  

  

Answer

(a)       Displacement reaction – Zinc displaces silver from silver nitrate.

(b)      Decomposition reaction- Potassium nitrate breaks down into potassium nitrite and oxygen gas on heating.

(c)       Double displacement reaction- Mutual ions exchange between both nickel nitrate and sodium hydroxide.

(d)      Decomposition reaction – Potassium chlorate breaks down into potassium chloride and oxygen gas.

(e)       Displacement reaction – Carbon displaces magnesium from magnesium oxide.

Q7. What is the difference between a combination and a decomposition reaction? Illustrate with suitable examples.

Answer

Combination reaction	Decomposition reaction
Two or more reactants combine to form a single product	A single compound breaks down into two more simpler substances
2Mg + O2 →2MgO	CaCO3 →CaO + CO2

 

Q8.Is there any oxidation without reduction? Justify your answer.

Answer

No, oxidation cannot occur without reduction.

Explanation

Oxidation is defined as the loss of electrons and reduction is the gain of electrons. These two processes occur together and known as redox reaction.

 When one substance losses electron(oxidised) then other substance must gain electrons(reduced).

Q9. Both combination reaction and displacement reaction fall in the category of redox reaction; Do you agree? If so, discuss this aspect with suitable examples.

Answer

Both combination reaction and displacement reaction fall in the category of redox reaction; Yes, I agree.

Explanation

A redox reaction involves both oxidation (loss of electrons) and reduction (gain of electrons).

Combination reaction as a redox reaction

   H₂ + Cl₂ →2HCl

    Hydrogen is oxidised

   H₂ →2H⁺  + 2e^-

  Chlorine is reduced

  Cl₂ + 2e^- →2Cl^-

Displacement reaction as a Redox reaction

 Zn + CuSO₄  ZnSO₄ + Cu

Zinc is oxidised

Zn → Zn²⁺   +2e^-

Copper is reduced

Cu²⁺ + 2e^-  →  Cu

Q10.Give two examples from everyday life situation where redox takes place. How will you prove it?

Answer

Rusting of iron and combustion of fuels are redox reactions from everyday life.

Rusting of iron

4Fe+ O₂ + xH₂O →2Fe₂O₃.xH₂O

Iron is oxidised to form iron ions and oxygen is reduced to form hydroxide ions.

A reddish-brown rust on iron articles. This is a redox reaction.

Combustion of fuels

CH₄ + 2O₂ →CO₂ + H₂O +heat

Carbon in methane is oxidised to carbon dioxide and oxygen is reduced, so this is a redox reaction.

Heat and light are released.

Q11.In the following reactions name the substances which are oxidised and reduced and also mention the oxidising and reducing agents:

  (a)   

(b)  

(c)   

Answer

(a)       Calcium is oxidised and chlorine is reduced.

(b)      Aluminium is oxidised to Al₂O₃ and MnO₂ is reduced to Mn.

(c)       Carbon mono oxide (CO)  is oxidised to CO₂ and Iron oxide (Fe₂O₃) is reduced to Fe.

Q12. Explain the following in terms of electron transfer

(a)       Oxidation

(b)      Reduction

Answer

(a)       Oxidation: The process in which a substance losses electron during the chemical reaction. This substance is oxidised.

              Na  → Na⁺  + e^-

(b)       Reduction: The process in which a substance gains electrons during a chemical reaction. The substance is reduced.

       Cl₂  + 2e^-  →2Cl^-

Q13. What is the law of definite proportion by volume? Explain.

Answer

Accoding to this law the volume of reacting gases and the volume of gaseous products are in a simple ratio.

2H_2(g) + O_2(g)  2H₂O_(g)

2 volume of hydrogen react with 1 volume of oxygen to form 2 volume of water vapour.

                                                       

NIOS Class 10 Science and Technology Solutions(212)

Chapter	Chapter Name
1	Measurement in Science and Technology
2	Matter in Our Surrounding
3	Atoms and  Molecules
4	Chemical Reactions and Equations
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8
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10