Chemical Reactions and Equations: Class 10 Science NCERT Chapter 1

Characteristics of NCERT Class 10 Chemistry Chapter 1 – Chemical Reactions and Equations 

Science is a subject that clarifies how our general surroundings are made of. Substance reactions are utilized to clarify the different cycles that occur around us. From rust to decomposition, compound reactions give a more inside and out knowledge into how subatomic communication and changes happen. As it were, part 1 of CBSE class 10 Science clarifies how a substance changes structure. 

Quick Revision Notes

Chemical Reactions and Equations: Balanced and unbalanced compound equations and adjusting of synthetic equations. 

What is a substance reaction Class 10? 

Chemical Reaction: The transformation of a concoction substance into another compound substance is known as Chemical Reaction. For instance: Rusting of iron, the setting of milk into curd, digestion of food, breath, etc. 

In a synthetic reaction, another substance is framed, which is totally different in properties from the first substance, so in a concoction reaction, a compound change happens. 

Just a revision of atoms happens in a concoction reaction. 

  • The substances which participate in a concoction reaction are called reactants. 
  • The new substances delivered because of a compound reaction are called products. 

Model: The consumption of magnesium noticeable all around to shape magnesium oxide is a case of a substance reaction. 

2Mg(s) + O2(g) 2MgO(s)

Prior to consuming in air, the magnesium lace is cleaned by scouring with sandpaper. 

This is done to eliminate the defensive layer of essential magnesium carbonate from the outside of the magnesium strip. 

Reactant: Substances which participate in a concoction reaction are called reactants. 

Model: Mg and O2. 

Product: New substance framed after a concoction reaction is known as a product. 

Model: MgO. 

Attributes of Chemical Reactions : 

(I) Evolution of gas: The substance reaction among zinc and dilute hydrogen gas development portrays sulphuric corrosive. 

Zn(solid) + H2SO4(aq) → ZnSO4(aq) + H2(gas) ↑ 

(ii) Change in Color: An adjustment describes the substance reaction between citric corrosive and purple shaded potassium permanganate solution in shading from purple to dull. 

An adjustment describes the compound reaction between sulfur dioxide gas and acidified potassium dichromate solution in shading from orange to green. 

(iii) Change in condition of substance: The ignition reaction of flame wax is described by an adjustment in the state from solid to liquid and gas (on the grounds that the wax is a solid, water framed by the burning of wax is a liquid at room temperature while, carbon dioxide created by the ignition of wax is a gas). Some concoction reactions can show more than one attribute. 

(iv) Change in temperature: The substance reaction between speedy lime water to frame slaked lime is portrayed by an adjustment in temperature (which is an ascent in temperature). 

The concoction reaction between zinc granules and dilute sulphuric corrosive is also described by an adjustment in temperature (which is an ascent in temperature). 

(v) Formation of precipitate: The substance reaction between sulphuric corrosive and barium chloride solution is described by the arrangement of a white precipitate of barium sulphate. 

BaCl2(aq) + H2SO4(aqueous) → BaSO4(s) (ppt) + 2HCl(aqueous) 

What is a substance Equation Class 10? 

Compound Equation: Representation of concoction reaction utilizing images and formulae of the substances is called Chemical Equation. 

Model: A + B → C + D 

In this equation, An and B are called reactants, and C and D are known as the products. The bolt shows the direction of the concoction reaction. Condition, assuming any, is composed commonly over the bolt. 

At the point when hydrogen responds with oxygen, it gives water. This reaction can be spoken to by the accompanying compound equation: 

Hydrogen + Oxygen → Water 

H2 + O2 → H2O 

In the principal equation, words are utilized, and in second, images of substances are being used to compose the synthetic equation. For accommodation, the notion of substance is utilized to speak to concoction equations. 

A compound equation is an approach to speak to the synthetic reaction concisely and educationally. 

A concoction equation can be divided into two kinds: Balanced Chemical Equation and Unbalanced Chemical Equation. 

(a) Balanced Chemical Equation: A balanced concoction equation has the quantity of atoms of every element equivalent on the two sides. 

Model: Zn + H2SO4 → ZnSO4 + H2 

In this equation, quantities of zinc, hydrogen, and sulfate are equivalent to the two sides, so it is a Balanced Chemical Equation. Mass can neither be made nor annihilated in a compound reaction says the Law of CONSERVATION OF MASS. To comply with this law, the all-out mass of elements present in reactants must be equivalent to the all-out mass of elements present in products. 

(b) Unbalanced Chemical Equation: If the quantity of atoms of every element in reactants isn’t equivalent to the quantity of atoms of every element present in the product, at that point, the substance equation is called the Unbalanced Chemical Equation. 

Model: Fe + H2O → Fe3O4 + H2 

In this model, various atoms of elements are not equivalent to different sides of the reaction. For instance, on the left-hand side, just one iron atom is available, while three iron atoms are available on the right-hand side. Hence, it is an unbalanced compound equation. 

Adjusting a Chemical Equation: To adjust the given or any synthetic equation, follow these means: 

Fe + H2O → Fe3O4 + H2 

Compose the number of atoms of elements present in reactants and in products in a table as appeared here. 

Name of atom No. of atoms in the reactant No. of atoms in the product
Iron 1 3
Hydrogen 2 2
Oxygen 1 4

Equalization the atom, which is most extreme in number on either side of a concoction equation. 

In this equation, the quantity of oxygen atoms is the greatest on the RHS. 

To adjust the oxygen, one needs to duplicate the oxygen on the LHS by 4, so that the quantity of oxygen atoms gets equivalent on the two sides. 

Fe + 4 × H2O → Fe3O4 + H2 

Presently, the quantity of hydrogen atoms gets eight on the LHS, which is more than that on the RHS. To adjust it, one needs to duplicate the hydrogen on the RHS by 4. 

Fe + 4 × H2O → Fe3O4 + 4 × H2 

From that point forward, the quantity of oxygen and hydrogen atoms gets equivalent on the two sides. The quantity of iron is one on the LHS, while it is three on the RHS. To adjust it, duplicate the iron on the LHS by 3. 

3 × Fe + 4 × H2O → Fe3O4 + 4 × H2 

Presently the quantity of atoms of every element gets equivalent on the two sides. Hence, this equation turns into a balanced equation. 

Name of atom No. of atoms in the reactant No. of atoms in the product
Iron 3 3
Hydrogen 8 8
Oxygen 4 4

After balancing, the above equation can be written as follows:

3Fe + 4H2O → Fe3O4 + 4H2.

In the wake of adjusting, the above equation can be composed as follows: 

3Fe + 4H2O → Fe3O4 + 4H2. 

To Make Equations More Informative: 

Composing the images of physical conditions of substances in a concoction equation: 

By composing the physical conditions of substances, a concoction equation turns out to be more instructive. 

The gaseous state is spoken to by image (g). 

The liquid state is spoken to by image (l). 

The solid-state is composed of image (s). 

The aqueous solution is composed of image (aq). 

Composing the condition in which reaction happens: The condition is commonly composed above or potentially underneath a synthetic equation bolt. 

In this way, by composing the images of the physical condition of substances and conditions under which reaction happens, a synthetic equation can be made more educational. 

What are the sorts of a synthetic reaction, Class 10? 

Kinds of Chemical Reactions: Combination Reaction, Decomposition Reaction, Displacement Reaction, Double Displacement Reaction, Neutralization Reactions, Exothermic – Endothermic Reactions, and Oxidation-Reduction Reactions. 

Kinds of Chemical Reactions: 

Synthetic reactions can be grouped in the following kinds: 

(I) Combination Reactions: Reactions in which at least two reactants join to shape one product are called Combination Reactions. 

An overall combination reaction can be spoken to by the compound equation given here: 

A + B → AB 


At the point when magnesium is singed noticeable all around (oxygen), magnesium oxide is shaped. In this reaction, magnesium is joined with oxygen. 

Mg(s) + O2(g) → 2MgO(s) 

Magnesium + Oxygen → Magnesium Oxide 

At the point when carbon is signed in oxygen (air), carbon dioxide is framed. In this reaction, carbon is joined with oxygen. 

C (s) + O2(g) → CO2(g) 

Carbon + Oxygen → Carbon dioxide 

(ii) Decomposition Reaction: Reactions in which one compound breaks down in at least two compounds or elements are known as Decomposition Reaction. A decomposition reaction is the polar opposite of a combination reaction. 

An overall decomposition reaction can be spoken to as follows : 

Abdominal muscle → A + B 


At the point when calcium carbonate is warmed, it disintegrates into calcium oxide and carbon dioxide. 

CaCO3(solid) latex-php-1 CaO(solid) + CO2(gas)

Calcium carbonate → Calcium oxide + Carbon dioxide 

At the point when ferric hydroxide is warmed, it decays and splits into water ferric oxide. 

2Fe(OH)3(solid) Fe2O3(solid) + 3H2O(liq)

Thermal Decomposition: The decomposition/splitting of a substance on warming is known as Thermal Decomposition. 

Example: 2Pb(NO3)2(s)latex-php-1 2PbO(s) + 4NO2(g) + O2(g)

Electrolytic Decomposition:Reactions in which compounds break down into more accessible compounds due to going of electricity are known as Electrolytic Decomposition. This is otherwise called Electrolysis

Model: When electricity is passed in water, it breaks down into hydrogen and oxygen. 

2H2O(l)latex-php 2H2(g) + O2(g)

Photolysis or Photo Decomposition Reaction: Reactions in which a compound deteriorates due to daylight are known as Photolysis or Photo Decomposition Reaction. 

Model: When silver chloride is placed in daylight, it decays into silver metal and chlorine gas. 

2AgCl(s) (white)latex-php-2 2Ag(s) (grey) + Cl2(g)

Photographic paper has a layer of silver chloride, which transforms into dim when presented to daylight. It happens on the grounds that silver chloride is vapid, while silver is a dim metal. 

(iii) Displacement Reaction: The synthetic reactions wherein a more receptive element displaces a less responsive element from a compound are Displacement Reactions. Displacement reactions are otherwise called Substitution Reaction or Single Displacement/substitution reactions. 

An overall displacement reaction can be spoken to by utilizing a substance equation as follows : 

A + BC → AC + B 

Displacement reaction happens just when ‘An’ is more responsive than B. On the off chance that ‘B’ is more responsive than ‘An’ at that point, ‘A’ won’t displace ‘C’ from ‘BC’ and reaction won’t be occurring. 


At the point when zinc responds with hydrochloric corrosive, it gives hydrogen gas and zinc chloride. 

Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) 

At the point when zinc responds with copper sulfate, it structures zinc sulfate and copper metal. 

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

(iv) Double Displacement Reaction: Reactions in which particles are traded between two reactants shaping new compounds are called Double Displacement Reactions. 

Stomach muscle + CD → AC + BD 


At the point when the solution of barium chloride responds with the solution of sodium sulfate, white precipitate of barium sulfate is framed alongside sodium chloride. 

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

At the point when sodium hydroxide (a base) responds with hydrochloric corrosive, sodium chloride and water are shaped. 

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

Note: Double Displacement Reaction, in which the precipitate is shaped, is otherwise called a precipitation reaction. Neutralization reactions are additionally instances of double displacement reactions.

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