NIOS Class 10 Science & Technology Chapter 4 Solution

NIOS Class 10 Science & Technology Chapter 4 Solution – Chemical Reaction And Equations

NIOS Class 10 Science & Technology Solution Chapter 4 Chemical Reaction And Equations. NIOS Class 10 Science & Technology Chapter 4 Question Answers Download PDF. NIOS Class 10 Science Notes.

NIOS Class 10 Science & Technology Chapter 4 Solution

Board NIOS
Class 10th  (Secondary)
Subject Science and Technology (212)
Topic Question Answer, Solution, Notes






1) Write a chemical equation for each of the following reactions:

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

Ans: -The required reaction is,

Zn + 2HCl —–> ZnCl2 + H2

(ii) When solid mercury (II) oxide is heated, liquid mercury and oxygen gasare produced.

Ans: – The required reaction is, 2HgO —-> 2Hg + O2


2) Balance the following chemical equations:

(i) H2SO4 (aq) + NaOH (aq) ⎯⎯→ Na2SO4 (aq) + H2O (l)

Ans: – H2SO4 + 2NaOH ——> Na2SO4 + H2O.


(ii) Al (s) + HCl (aq) ⎯⎯→ AlCl3 (aq) + H2 (g).

Ans: – 2Al + 6HCl — 2AlCl3 + 3H2.


3) What is a balanced chemical equation? Why should a chemical equation be balanced?

Ans: – The representation of the reaction between the two different compound or the same compound dissociate with various elements are represented by the chemical equation. As we know from the laws of conservative of mass that the mass of reactant and products will be same after any reaction so all the equation of chemical reaction will be balanced after the reaction.



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

(i) AgNO3 (aq) + HCl (aq) ⎯⎯→ AgCl (s) + HNO3 (aq)

(ii) MnO2 (s) + 4HCl (aq) ⎯⎯→ MnCl2 (aq) + 2H2O (l) + Cl2 (g)

(iii) 4Na (s) + O2 (g) ⎯⎯→ 2Na2O (s).

Ans: – From the upper reaction we came to this conclusion that the except the first reaction all the other are the example of the redox reaction. As in the first reaction is the displacement reaction so it will not be aredox reaction.


2) Identify the substances which are oxidized and the substances that are reducedin the following reactions:

(i) H2 (g) + Cl2 (g) ⎯⎯→ 2HCl (g).

Ans: – The element of the upper reaction H2 is oxidized and Cl2 is reduced and make the compound hydrogen chloride.


(ii) H2 (g) + CuO (s) ⎯⎯→ Cu (s) + H2O (l).

Ans: – The CuO is reduced to copper and the H2 is oxidized and became water after this reaction.


(iii) Zn (s) + 2AgNO3 (aq) ⎯⎯→ Zn (NO3)2 (aq) + 2Ag (s).

Ans: – The Zn after oxidation make the compound zinc nitrates and the silver nitrate after the reduction convert to silver.



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

(a) Carbon + oxygen ⎯⎯→ Carbon dioxide.

Ans: – The chemical reaction is, C +O2 —–> CO2.


(b) Hydrogen + Chlorine ⎯⎯→ Hydrogen chloride.

Ans: – H2 + 2Cl —–> 2HCl.


(c) Barium chloride + Sodium sulphate ⎯⎯→ Barium sulphate + sodium chloride.

Ans: – BaCl2 + Na2SO4 ——> BaSO4 + 2NaCl.

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 600°C temperature, and the product obtained is ammonia.

Ans: – The balance chemical equation is,

N2(g) + 3 H2(g) 2NH3(g).


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

Ans: – NaOH(g) + HCl(l) —–> NaCl(s) + H2O(l).


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

Ans: – P4 (g) + 20Cl(g) —-> 4PCl5(g)


C.) Balance the following chemical reactions:

(a) Ca(OH)2 + HNO3 ⎯→ Ca(NO3)2 + H2O.

Ans: – Ca(OH)2 + 2HNO3 ⎯→ Ca(NO3)2 + 2H2O.


(b) BaCl2 (aq) + H2SO4 (aq) ⎯→ BaSO4 (s) + HCl (aq).

Ans: – BaCl2 + H2SO4 ⎯→ BaSO4 + 2HCl.


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

Ans: – CuSO4 + Zn ⎯→ ZnSO4 + Cu.


(d) H2S (g) + SO2 (g) ⎯→ S (s) + H2O (l).

Ans: – H2S + SO2 ⎯→ 2S + H2O.


(e) BaCl2 (aq) + Al2(SO4)3 (aq) ⎯→ AlCl3 (aq) + BaSO4 (s).

Ans: – 3BaCl2 + Al2(SO4)3  2AlCl3 + 3BaSO4.


(f) Pb (NO3)2 (aq) + Fe2(SO4) 3(aq) ⎯→ Fe(NO3)3 (aq) + PbSO4 (s).

Ans: – 3Pb(NO3)2 + Fe2(SO4)3  2Fe(NO3)3 + 3PbSO4


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

Ans: – Ca(OH)2 + CO2 ⎯→ CaCO3 + H2O.


(h) Aluminium + Copper (II) chloride ⎯→ Aluminium chloride + copper.

Ans: – Al + 3CuCl2 ⎯→ AlCl3 + 3Cu.


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

Ans: – CaCO3 + 2 HClCaCl2 + H2O + CO2.


2) What is a balanced chemical equation? Write 3 characteristics of a balanced chemical equations?

Ans: – The example of a balance chemical equation is,

H2 + 2Cl ⎯→ 2HCl.

The characteristics of balance chemical reaction is,

  •  It denote the different oxidation states of different elements that participate in the reaction.
  • The property of that element or compound would be know to us.
  •  The valency of that molecule is known to us.


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

Ans: – The example of displacement reaction is,

Zn + 2HCl —-> ZnCl2 + H2.

The example of double displacement reaction is,

BaCl2 + H2SO4 ⎯→ BaSO4 + 2HCl.


4) What happens when dilute hydrochloric 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 and is classified as a decomposion reaction.

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

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

Ans: – Option (a).


7) What do you mean by an exothermic reaction? Give a suitable example.

Ans: – The exothermic reaction is a reaction where the heat is produced and the most of the combination reaction is the example of this exothermic reaction.

C +O2 ⎯→ CO2 + Heat.


8) Classify each of the following reactions as combination, decomposition, displacement or double displacement reactions:

(a) Zn (s) + 2AgNO3 (aq) ⎯⎯→ Zn(NO3)2 + 2Ag (s).

Ans: – Displacement reaction.


(b) 2KNO3 (s) heat ⎯⎯⎯→ 2KNO2 + O2 (g).

Ans: – Decomposition reaction.


(c) Ni (NO3)2 (aq) + 2NaOH (aq) ⎯⎯→ Ni(OH)2 (s) + 2NaNO3 (aq).

Ans: – Double displacement reaction.


(d) 2KClO3 (s) heat ⎯⎯⎯→ 2KCl (s) + 3O2 (g).

Ans: – Decomposition reaction.


(e) MgO (s) + C (s) ⎯⎯→ CO (g) + Mg (s).

Ans: – Combination reaction.


9) What is the difference between a combination and a decomposition reaction?

Illustrate with suitable examples.

Ans: –

Combination reaction

 Decomposition reaction

Two or more elements from a compound by adding together. One compound decomposes to various elements.
C + O2 —-> CO2 2KClO3 —–> 2KCl + 3O2.


10) Is there any oxidation without reduction? Justify your answer.

Ans: – There is no possibility of oxidation without the reduction process as if any electron is lost by one element that should be accepted by the other element so in a reaction oxidation and reduction happen simultaneously.


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

Ans: – In a redox reaction the oxygen and hydrogen are accepted or loses for the reaction so this will not be happened in all the combination and displacement reaction. As in a displacement reaction or in a combination reaction just substrate are changes.


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

Ans: – The example of everyday life situation of redox reaction is,

  • Rancidity of different food items.
  • Corrosion in iron.


13) In the following reactions name the substances which are oxidized and reducedand also mention the oxidizing and reducing agents:

(a) Ca (s) + Cl2 (g) heat ⎯⎯⎯→ CaCl2 (s).

Ans: – In this reaction, Ca is oxidized so it is a reducing a agent. And Cl is reduced then it is a oxidized agent.


(b) 3MnO2 (s) + 4Al (s) heat ⎯⎯⎯→ 3Mn (l) + 2Al2O3 (s).
Ans: – In the upper reaction, Al is oxidized so it is a reducing agent. And MnO2 is reduced so it is oxidizing agent.


(c) Fe2O3 (s) + 3CO (g) heat ⎯⎯⎯→ 2Fe (s) + 3CO2 (g).
Ans: – Here CO is oxidized so it will be a reducing agent and Fe2O3 is reduced so it will be an oxidizing agent.


14) Explain the following in terms of electron transfer:

(a) Oxidation (b) Reduction.

Ans: – Oxidation: – It is a reaction in which oxygen is gain and hydrogen is loosed by the elements or the compound.

Reduction: – It is process in which oxygen is looses or hydrogen is gain by the element or the compound.


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

Ans: – According to the laws of proportion of volume the volume of the reactant and the product will be same this this given by the scientific research of Gay-Lussac.

Updated: February 21, 2022 — 11:04 am

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