Chemical Reaction and Equation Class 10 Notes

Chemical Reaction and Equation Class 10 Notes will help you quickly grasp the key concepts of chemical reactions and equations.

Chemical Reactions and Equations


You’ll be able to better understand how these concepts are applied in the real world. These notes are an essential tool for any student looking to get ahead in chemistry class.

Mind blowing 10th class chapter 1, chemistry notes of chemical reactions and equations by Dr. M S Khan. Get complete lesson here.

Chapter 1 – Chemical Reactions and Equations

You must have observed that when a Silver material is kept in the open for a long period of time, it gets corroded. Similar way, when we cook food, rice get changed into cooked rice.

Both the examples of chemical changes. Because formation of new substances takes place with different chemical properties and irreversible.

What is relation between chemical changes and chemical reaction? When we chemical changes were represented by chemical formula and equation, is called chemical reaction.

How we determine whether a chemical reaction takes place?

The chemical reaction can be confirmed by any or all of the following properties observed during chemical changes –

  • Change in energy
  • change in temperature
  • change in state
  • change in colour
  • when gas is / are released.

Examples of chemical changes

  • Coagulation of milk.
  • An iron utensils is left exposed to humid atmosphere.
  • Grapes(fruits) get fermented.
  • Raw food are cooked.
  • Food gets digested in our digestive system.
  • Cellular respiration and photosynthesis.

All those example shows formation of new product and change its chemical and physical properties. All these above process are totally Irreversible.

Don’t confuse with physical changes, in physical changes no new product form and reversible. Conversion of liquid water into solid ice water its example of physical changes. Solid ice water can change into you again liquid water.

Activity 1.1 – Burning of magnesium ribbon

  • Take 2 centimetre long magnesium ribbon.
  • Clean by rubbing with Sandpaper. Maybe some impurity present on magnesium ribbon.
  • Magnesium ribbon hold with tongs above the spirit lamp or burner.
  • Collect the ash on watch-glass.


  • Burn of magnesium ribbon keeping it as far as possible from your and your teacher eyes and mouth.
  • If possible wear eye protection. You should do this activity in the presence of teacher.

What do you observe?

Mg + O2 > MgO

In this activity magnesium react with oxygen with certain ignition temperature and produce magnesium oxide.

You can absorb magnesium oxide Ribbon burning with dazzling white flame and finally changed into white powder which collected on – (ash form) on watch-glass.

Activity 1.2 – Reaction between Lead Nitrate and potassium iodide

Lead(II) nitrate reacts with potassium iodide and produces lead(II) iodide and potassium nitrate. Its example of of double displacement and precipitation reaction.

Observation – formation of yellow colour precipitate.

Activity 1.3 – reaction of Zinc with dilute hydrochloric acid and sulphuric acid

Almost all Metal are reactive with acid like hydrochloric acid and sulphuric acid. When zinc react with hydrochloric acid form zinc chloride and hydrogen gas. When zinc react with sulphuric acid form zinc sulphate and hydrogen gas.


Hydrogen gas evolved in the form of bubble and temperature increases conical flask. Because this reaction are exothermic in nature.

1.1 chemical Equations

Now you are aware of burning of of magnesium ribbon. Burning of magnesium is less informative and writing in sequence quite long.

In simple way this chemical changes we can write in the form of word equation.

Magnesium + oxygen – – > magnesium oxide

Magnesium and oxygen are react while magnesium oxide is a product. In word equation shows chemical changes of reactant into product by Arrow placing between them.

Reactant written left hand side and if more than one reactant use plus sign between them. Product written right hand side and if more than one product use plus sign between them.

1.1.1 – Writing a chemical equation

A chemical equation more concise and useful representation of chemical reaction. In chemical equation used chemical formula instead of words using in a chemical reaction.

Magnesium + oxygen – – > magnesium oxide, this word equation can written into chemical equation.

Mg + O2 → MgO

1.1.2 – Balance and unbalance chemical equation

Know easy way to balancing chemical equations. Definition of of unbalanced chemical reaction – In a chemical reaction total mass of the all reactants are unequal to total mass of the all the products. Unbalanced chemical equation also called skeletal chemical equation.

Definition of of balanced chemical reaction – In a chemical reaction total mass of the all reactants are equal to total mass of the all the products.

Why we need to balance a skeletal chemical equation?

Conservation of mass – Mass can neither be created nor be destroyed in a chemical reaction.

According to conservation of mass, mass of reactant should be equal to mass of product. Therefore we balance the unbalance or skeletal chemical equation.

How balance the unbalance chemical equation?

We can balancing the chemical equation with simple trick through hit and trial methods.

Balancing chemical equations examples

Step 1 – if examiner given to you word equation, translate the equation into chemical equation.

Word equation

Zinc + Sulphuric acid → Zinc sulphate + Hydrogen

Translate into chemical equation

Zn + H2SO4 → ZnSO4 + H2

Converting word equation into chemical equation required knowledge of valency and no. charge of cation and anion.

Step 2 – check reaction balance or unbalance

Count number of elements present in left side of reactant and right side of product. If number of element both side are equal, that means reaction is balanced while not equal that means reaction is unbalanced.


Zn + H2SO4 → ZnSO4 + H2

Zn in reactant and product number is equal. Same as number of hydrogen and sulphate are also equal both the reactant and product side. This chemical equation is balance chemical equation.

Fe + H2O → Fe3O4 + H2

In this reaction 1 Fe present in reactant while 3 Fe present in product. Two hydrogen present in reactant and two hydrogen also present in product. One oxygen present in reactant while four oxygen present in in product.

In chemical reaction any one reactant or product number an equal, that chemical reaction classify into unbalanced chemical reaction. We should balance this unbalanced chemical equation.

Step 3 – We have only the option equalising number of element in reactant and product by multiplying by coefficient (digit). My advice to you first equalise the metal by best possible coefficient. Example

3Fe + H2O → Fe3O4 + H2

Here Fe (reactant) multiplying by 3, because 3 Fe present in product.

3Fe + 4H2O → Fe3O4 + H2

Balancing number of oxygen – Water (reactant) multiply by 4 because for oxygen present in in product (Fe3O4).

3Fe + 4H2O → Fe3O4 + 4H2

Balancing Number of hydrogen – now reactant side 8 hydrogen present while product side only two hydrogen. We should product side hydrogen multiply by 4.

Step 4 – check again reaction balanced or not. Number of iron reactant and product side is 3. 8 hydrogen present in reactant and product side also 8 hydrogen present. 4 oxygen present in reactant while 4 oxygen also present in product.

Therefore this chemical equation 100% balance chemical equation.

Step 5 – In balance chemical equation you should also write symbol of physical state.


3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)

In a balance chemical equation, solid state symbolised as (s), Aquas (aq) liquid (l), & gas (g). If gas evolve symbolised upward arrow while precipitate formation (solid) symbolise by downward arrow.

1.2 – Types of chemical reactions

  • Combination reaction and exothermic
  • Decomposition reaction and endothermic
  • Displacement reaction
  • Double displacement reaction and precipitation
  • Oxidation and reduction (Redox reaction).

1.2.1 – Combination reaction

Combination reaction is a type of chemical reaction in which two or more reactants react together form a large single product is known as combination reaction.


CaO(s) + H2O(l) → Ca(OH)2(aq)

Calcium oxide (Quick lime) react with water to form a single product calcium hydroxide (Slaked lime).

When chemical reaction produces heat, during reaction is known as exothermic chemical reaction. Generally all combination reactions are exothermic chemical reaction.

White washing Chemistry

Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)

A slow chemical reaction you can show during whitewashing. Calcium hydroxide react with carbon dioxide to form calcium carbonate and water. After few days gives shiny finish to the wall. Calcium carbonate commonly called marble.

Some more example of combination reactions

Burning of coal

C(s) + O2(g) → CO2(g)

Formation of water

2H2(g) + O2(g) → 2H2O(l)

Burning of natural gas

CH4(g) + 2O2 (g) → CO2 (g) + 2H2O (g) (1.17)

Cellular respiration

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

Decomposition of vegetable matter into compost is an example of endothermic reaction but not the example of combination reaction.

Activity 1.4 – Formation of calcium hydroxide

Take small amount calcium oxide in a beaker and slowly add some water.

CaO(s) + H2O(l) → Ca(OH)2(aq)


When you putting finger on the beaker you feel hotter. Because this combination reaction is release heat, heat releasing reaction called exothermic chemical reaction.

1.2.2 – Decomposition reaction

Decomposition reaction is a type of chemical reaction in which large reactant breaks into many products while applying energy is known as decomposition reaction.

Decomposition reaction classify on the basis of form of energy. When applying –

  • Heat – thermal decomposition
  • Electricity – electrolysis
  • Sunlight – photolysis / photolytic decomposition

Thermal decomposition / Thermochemical equation

Thermal decomposition reaction is a type of decomposition reaction in which large reactant breaks into many products while applying heat is known as decomposition reaction.


1 – Decomposition of ferrous sulphate crystal

FeSO4.7H2O – – heat- – > FeSO4 + 7H2O

Ferrous sulphate crystal green colour change into white colour of ferrous sulphate.

2 – Decomposition of ferrous sulphate

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

Heating of ferrous sulphate produce ferric oxide, Sulphur dioxide and sulphur trioxide.

3 – Decomposition of calcium carbonate

CaCO3(s) → Heat CaO(s) + CO2(g)

This chemical reaction used in Cement factory. Calcium carbonate also called limestone or marble.

4 – Decomposition of Lead Nitrate

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

When Lead Nitrate decompose by heat produce lead oxide which is brown colour fumes.

Activity 1.5 – Decomposition of ferrous sulphate crystal

Take about 2 gram ferrous sulphate crystal in dry boiling tube and not the colour of ferrous sulphate crystal.

Slowly heat the boiling tube over the flame of lamp spirit.

Precaution – Make sure do not point the mouth of boiling tube at your teacher and for yourself.

Observation – change the colour ferrous sulphate crystal green into white or light green ferrous sulphate.

Activity 1.6 – Thermal decomposition of of late nitrate powder.

Take approx 2 gram Lead Nitrate powder in a boiling tube hold with tongs.

Slowly heat the boiling tube over the flame of lamp spirit.

Precaution – Make sure do not point the mouth of boiling tube at your teacher and for yourself.

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Observation – Formation of brown fumes is a sign of of chemical reaction takes place.


Electrolysis reaction is a type of decomposition reaction in which large reactant breaks into many products while applying electricity is known as Electrolysis reaction.

Activity 1.7 – Electrolysis of water

Setup – Drill make two holes at bottom of plastic mug, make sure fit rubber stoppers in the holes. Two carbon electrodes insert into rubber stoppers.

Then connect two electrodes respective terminals of 6 volt battery and key (switch). Fill the mug with water such that the electrodes are fully immersed. Add a few drops of dilute sulphuric acid to water mug.Take two test tubes filled with water and invert over them the two carbon electrodes.

Working – Now, on the key and leave the apparatus undisturbed for 5 minutes.

Observations – Formation of bubbles

at both the electrodes. These bubbles are displace water in the test tubes.Removing each test tube carefully and test with candle.

2H2O – – – > 2H2 +O2

If candle giving pop sond, that means hydrogen gas evolved. If you do not produce pop sound that means Oxygen gas evolved.


Electrolysis of water produce 2 mole of hydrogen and 1 mole of Oxygen. Hydrogen and oxygen formation ratio is 2:1.

Photolytic decomposition / photolysis

Photolytic decomposition reaction is a type of decomposition reaction in which large reactant breaks into many products while applying light is known as photolysis reaction.


Photolytic decomposition of silver chloride

2AgCl(s) → 2Ag(s) + Cl2(g)

Silver chloride turns grey in the presence of Sunlight.

Photolytic decomposition of Silver Bromide

2AgBr(s) → 2Ag(s) + Br2(g)

This chemical reaction earlier days use as black and white photography.

Why decomposition reaction considered as endothermic chemical reaction?

All types of decomposition reaction required energy to complete reaction. If any reaction gain energy (heat) is called endothermic reaction.

1.2.3 – Displacement reaction

Displacement reaction is a type of chemical reaction in which more reactive element replace the less reactive elements of their compound is known as displacement reaction.


Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

More reactive iron replace the copper from copper sulphate.

Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)

More reactive zinc displace copper from copper sulphate.

Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s)

More reactive lead displays the less reactive copper from copper chloride.

PbCl2(aq) + Cu(s) → no reaction takes place

In this case copper is less reactive than lead, therefore no displacement reaction occurs.

Activity 1.9 – reaction between iron nail and copper sulphate

Setup – Take a test you fit with stand, hang clean iron nail with the help of thread. Put copper sulphate solution into the test tube.

Observation – after 20 minutes you can absorb blue colour of solution convert into to White or light blue colour.

Result –

Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

This reaction takes place. That means blue colour copper sulphate convert into to White or light blue colour iron sulphate.

1.2.4 – Double displacement and precipitation reaction

Double displacement reaction is a type of chemical reaction in which more reactive element replace twice the less reactive elements of their compound is known as double displacement reaction.

NCERT Definition – Such reactions in which there is an exchange of ions between the reactants are called double displacement reaction.


Na2SO4(aq) + BaCl2(aq) → BaSO4(s, ppt) + 2NaCl(aq)

In this reaction water insoluble substance Barium sulphate is formed is known as precipitate. Any chemical reaction produce precipitate is called precipitation reaction.

Activity 1.10 – Formation of Barium sulphate precipitate

Take to clean two test tube, one test tube filled 3ml sodium sulfate and another test tube filled with 3 ml Barium Chloride solution.

Mixing both the solution, still solid white substance formed.

Observation – if white solid (precipitate) Barium sulphate formed that means double displacement reaction takes place.

1.2.5 – Oxidation and reduction ( Redox reaction)

Oxidation is a type of chemical reaction in which substance gain oxygen and removal of hydrogen is known as oxidation.

Reduction is a type of chemical reaction in which substance loss Oxygen and gain of hydrogen is known as reduction.

In a same chemical reaction oxidation and reduction takes place simultaneously is called Redox reaction.

Oxidized reactant called reducing agent while reduced reactant is called oxidizing agent.


ZnO + C → Zn + CO

Zinc oxide reduced because zinc loses oxygen, therefore zinc oxide is oxidising agent. Another reactant carbon gain of oxygen, carbon get oxidized and behave like reducing agent.

Activity 1.11 – Redox reaction

Take a China dish, wire gauge, tripod stand and burner, set up like this diagram. 1 gram copper powder heat slowly.

Observation – surface of copper powder become black.

Result –

2Cu + O2 → 2CuO

Black colour copper oxide form in this reaction, distraction symbolised as oxidation and reduction (Redox reaction) takes place.

1.3 – Have you observed the effect of Oxidation reaction in everyday life?

1.3.1 Corrosion

When a metal is attacked by substances around it such as moisture, acids, carbonate and sulphate etc., it is said to corrode and this process is called corrosion.

When iron corrode, its colour change to reddish Brown is called rusting of iron. When silver corrode colour change to black while copper change into green colour.

1.3.2 Rancidity

When fat and or oil containing dry food substance are oxidized, and its smell and taste change is called rancid food and this process known as rancidity.

Usually rancidity of prevent by filling antioxidant like nitrogen gas in air tight container.

Conclusion Points

Chemical Reaction and Equation Class 10 Notes are the perfect way to learn about important topics in chemistry. With clear and concise explanations, these notes provide students with a great resource to ace their class.

In conclusion,the notes for chemical reaction and equation class 10 provides a detailed and comprehensive guide for students. It covers all the important concepts and topics related to the topic.

The notes are well organised and easy to understand. They provide a good foundation for students who want to learn more about this topic.

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