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CBSE Class 10th Science Board Exam 2021: Important Chemical Reactions

Mayank Uttam

Check chapter-wise important chemical reactions of CBSE Class 10th Science. The list of chemical reaction available here is from Class 10th Science NCERT textbooks, previous years' papers and the latest sample paper. Science is one of the important subjects of CBSE Class 10th and students preparing for this subject often search chemical reactions important for Class 10 Science Board Exam 2021. In this article, you will get important chemical reactions, resources (such as Sample Papers, Syllabus etc.) and few tips for the preparation of the exam. Also, check deleted CBSE Class 10 Science Syllabus 2021. As some topics are excluded from the syllabus including some chemical reactions.

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Chapter-wise Important Chemical Reactions for Class 10 Science Board Exam 2020-21 are given below:

Chapter 1: Chemical Reactions and Equations

• Mg + O2 → 2MgO

• Zn + H2SO4→ ZnSO4 + H2

• 3Fe + 4H2O → Fe3O4 + 4H2

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

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 (Quick lime)                                                                     (Slaked lime)

• C(s) + O2 (g) → CO2 (g)

• 2 H2 (g) + O2 (g) → 2H2O (l)

• CH4 (g) + 2 O2 (g) → CO2 (g) + 2H2O (g)

• C6H12O6 (aq)    +          6O2 (aq)           →       6 CO2 (aq)       + 6 H2O (l)       + energy

  (Glucose)                     (Oxygen)        

• 2FeSO4(s)                    →        Fe2O3 (s)          +          SO2 (g)            +          SO3 (g)

  (Ferrous sulphate)                  (Ferric oxide)

• CaCO3(s)         +          Heat                 →        CaO (s)            +          CO2 (g)

 (Limestone)                                                     (Quick lime)

• 2Pb (NO3)2 (s)              +          Heat    →        2PbO(s)           +          4NO2 (g)          +          O2 (g)

(Lead nitrate)                                                   (Lead oxide)               (Nitrogen dioxide)

• Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl (aq)

• ZnO + C →Zn + CO

• MnO2 + HCl →MnCl 2 + 2H2O + Cl2

Chapter 2: Acids, Bases and Salts

• Reaction of acids and bases with metals:

Acid + Metal → Salt + Hydrogen gas


2 NaOH           +          Zn        →        Na2ZnO2          +          H2

                                                            (Sodium zincate)

Reaction of base and acid to give salt (neutralisation reaction):

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Other reactions:

Chapter 3: Metals and Non-metals

• Chemical properties of metals:

Metal + Oxygen → Metal oxide


• 2Cu + O2 → 2CuO

• 4Al + 3O2 → 2Al2O3

Aluminium oxide reacts in the following manner with acids and bases:

• Al2O3 + 6 HCl → 2 AlCl3 + 3 H2O

• Al2O3 + 2 NaOH → 2 NaAlO2 + H2O

Sodium oxide and potassium oxide dissolve in water to produce alkalis:

• Na2O(s) + H2O (l) → 2 NaOH (aq)

• K2O(s) + H2O (l) → 2 KOH (aq)

Reactions of Metal with water

Metal + Water → Metal oxide + Hydrogen

Metal oxide + Water → Metal hydroxide


• 2K(s) + 2H2O (l) → 2KOH (aq) + H2 (g) + heat energy

• 2Na(s) + 2H2O (l) → 2 NaOH (aq) + H2 (g) + heat energy

• Ca(s) + 2 H2O (l) → Ca (OH)2 (aq) + H2(g)

• 2 Al (s) + 3H2O (g) → Al2O3 (s) + 3H2 (g)

• 3 Fe (s) + 4H2O (g) → Fe3O4(s) + 4H2 (g)

Check formation of NaCl and its electron dot structure form NCERT Textbook.

Chemical reactions related to extraction of metal are also important for CBSE 10th Science Board Exam 2019:

Chapter 4: Carbon and its Compounds

Chemical Properties of Carbon Compounds

Combustion of carbon and its compounds:

(i) C + O2 → CO2 + heat and light

(ii) CH4 + 2O2 → CO2 + 2H2O + heat and light

(iii) CH3CH2OH + 2O2 → 2CO2 + 3H2O + heat and light

Oxidation of carbon compounds:

Conversion of alcohol to carboxylic acid

Addition Reaction:

Hydrogenation of vegetable oils using a nickel catalyst:

Properties of Ethanol:

Reactions of Ethanol with sodium –

2Na + 2CH3CH2OH →                        2 CH3CH2O–Na+         +         H2

                                                (Sodium ethoxide)

Heating of ethanol:

Heating ethanol at 443 K with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene –

Esterification reaction:

Esters (sweet-smelling substances used in making perfumes and as flavouring agents) are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester –


Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap.

Chapter 5 Periodic Classification of Elements

We don't find any important chemical reaction in this chapter.

Chapter 6: Life Processes

Process of photosynthesis

Chapter 7: Control and Coordination

We don't find any important chemical reaction in this chapter.

Chapter 8: How do Organisms Reproduce?

We don't find any important chemical reaction in this chapter.

Chapter 9: Heredity and Evolution

We don't find any chemical reaction in this chapter.

Chapter 10: Light – Reflection and Refraction

This chapter doesn’t have any chemical reaction.

Chapter 11: The Human Eye and the Colourful World

This chapter doesn’t have any chemical reaction.

Chapter 12: Electricity

We don't find any important chemical reaction in this chapter.

Chapter 13: Magnetic Effects of Electric Current

We don't find any important chemical reaction in this chapter.

Chapter 14: Sources of Energy

Nuclear fusion: Most commonly hydrogen or hydrogen isotopes to create helium, such as

2H + 2H → 3He (+ n)

It releases a tremendous amount of energy

Chapter 15: Our Environment

Formation of ozone:

Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen (O2) molecule. The higher energy UV radiations split apart some moleculer oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone as shown—

Chapter 16: Management of Natural Resources

We don't find any important chemical reaction in this chapter.

Quick Tips for Preparation of CBSE Class 10 Science Paper 2021

1. Follow Latest CBSE Class 10 Science Syllabus 2020-21
2. Revise Previous Year Question Papers of Class 10
3. Refer NCERT textbooks or Class Notes
4. Solve CBSE Class 10 Sample Papers and Practice Papers

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