Chemical reaction types_grade_10

CBSE - 10 Chemical Reactions and Equations
Chemistry Types of Chemical Reactions

Lesson Objectives

After completing this lesson
you will be able to classify
the chemical reaction and
identify the type of chemical
After completing this lesson you will be able to reaction.

• classify the chemical reaction
• identify the type of chemical reaction


In a chemical reaction , a
reactant and a reagent combine
and form a new product and a
by-product.

Reactant + Reagent  Product + By-product


Let us watch this reaction.

What happens in this reaction?


Magnesium ribbon burns in air
to become magnesium oxide.

2Mg + O2 2MgO
Magnesium Magnesium oxide


We can classify reactions into
combination reaction,
displacement reaction,
Types of reactions decomposition reaction,
double displacement reaction,
neutralisation reaction, red-ox
Combination reaction reactions, thermal dissociation
Displacement reaction reaction and irreversible and
irreversible reactions.
Decomposition reaction
Double displacement reaction
Neutralisation reaction
Oxidation - reduction reaction
Thermal dissociation reaction
Reversible and irreversible reaction


Combination Reaction In this simple combination
reaction, magnesium
combines with oxygen to form
magnesium oxide.

2Mg + O2  2MgO

Magnesium ribbon
Magnesium oxide powder


Interactivity
Click the view answer button
to find out the product.

Na + Cl2  ? (on heating)

What could be the product?

View answer


Sodium and chlorine combine
on heating to form sodium
Heat chloride.
2 Na + Cl2 2 NaCl

Sodium metal Chlorine gas Sodium chloride


Sulphur combines with iron on
heating to give iron sulphide.
Fe + S FeS

Iron Iron powder

Sulphur
powder

Mixing iron Iron sulphide powder
and sulphur


Let us see some more
examples of combination
reaction. Nitrogen combines
with hydrogen and gives
ammonia on heating. Similarly
sulphur combines with oxygen
Heat to form sulphur dioxide.
N2 + 3H2 2NH3

S + O2 SO2


Interactivity
Click on the view answer
button to find out the product.

Complete the reactions

H2 + Cl2 __?__

View answer


Hydrogen and chlorine
combine to form hydrogen
chloride.

H2 + Cl2 2HCl


Displacement Reaction We can classify displacement
reactions further into metal-
metal displacement and
metal-nonmetal displacement
Displacement Reaction reactions.

Metal-metal Metal - non-metal


Metal – Metal Displacement According to reactivity series
the most reactive metals
replace the less reactive
metals.


Interactivity

Complete the reaction

Cu + AgNO3  _____ + _____

View answer


Since copper is more reactive
Cu + 2AgNO3  2Ag + Cu(NO3)2 than silver copper replaces
silver in this reaction.

Copper coil

Silver nitrate solution Silver and copper nitrate solution


Metal – Non-metal Displacement Sometimes, a metal displaces
a non-metal. Different metals
have different reactivities with
various non-metals such as
2Na + 2H2O  2NaOH + H2 ↑ oxygen and hydrogen. For
example, sodium reacts
violently with water, even at
room temperature to replace
hydrogen, the non-metal.

Reaction of sodium with water


Hydrogen in water is replaced
by magnesium only on
heating.

Heat
Mg + H2O MgO + H2 ↑

Magnesium powder Magnesium oxide


Copper does not react with
Order of reactivity of metals with water water. Sodium is more
reactive with water. Thus we
can predict the non-metal
Na > Mg > Fe > Cu displacement by the order of
reactivity.

Reaction of sodium with water


Interactivity
to find out the products.

Iron reacts with steam when it is red hot.
Complete the equation

Fe + H2O Red hot _____ + ______

View answer


Iron replaces hydrogen from
water.

Red hot
3Fe + 4H2O Fe3O4 + 4H2 ↑


Decomposition Reaction When a single compound
breaks up into two or many
simpler substances it is called
decomposition reaction.

Decomposition

Breaking of single compound into simpler
substances


When we heat lead nitrate it
becomes lead oxide with the
evolution of oxygen gas and
2Pb(NO3)2 Heat 2PbO + 4NO2↑ + O2 ↑ brown fumes of nitrogen
dioxide.

Brown fumes of
nitrogen dioxide


Interactivity Watch this experiment and
Why does blue copper sulphate answer the question.

solution become white on heating?

View answer


Blue copper sulphate pentahydrate undergoes
decomposition on heating to give white
anhydrous copper sulphate and water vapour.

CuSO4.5H2O  CuSO4 + 5H2O


Double Displacement Reaction
Two compounds react to form
different compounds by mutual
exchange of ions or atoms in a
double displacement reaction.

Double Displacement
Mutual exchange of ions in two different
compounds


When silver nitrate reacts
AgNO3 + KCl  AgCl + KNO3 with potassium chloride, it
gives silver chloride and
potassium nitrate.

Silver nitrate solution Silver chloride solution
(Colourless) (Curdy white precipitate)


Interactivity
What happens when barium chloride is treated with
sodium sulphate?

View answer


Barium chloride gives a white precipitate of
barium sulphate and sodium chloride.

BaCl2 + Na2SO4  BaSO4 ↓ + 2NaCl


Neutralisation Reaction Neutralisation is also an
example of double
displacement reaction.
Acid reacts with base to
form salt and water.

Neutralisation
Acid + Base Salt + Water


Equimolar mixture of sodium
hydroxide and hydrochloric
Neutralisation
acid result neutralisation
NaOH + HCl NaCl + H2O mixture, containing sodium
chloride salt and water .

Did you know?

When we add a few
drops of phenolphthalein
indicator in a
neutralisation mixture
with a slight excess of
alkali it gives pale pink
colour.

Pale pink colour of neutralisation
Colourless neturalisation mixture with slight excess of
mixture NaOH


Interactivity

Complete the reaction

Ca(OH)2 + H2SO4  ____ + ___

View answer


Calcium hydroxide reacts with
sulphuric acid to form calcium
Ca(OH)2 + H2SO4  CaSO4↓ +2H2O sulphate and water.

Calcium hydroxide

Calcium sulphate

Sulphuric acid


Oxidation - Reduction Combustion of gasoline,
burning of wood and
burning of food in our body
are examples of oxidation.


An oxidation reaction
occurs as a result of either
the addition of oxygen or
the removal of hydrogen. A
reduction reaction occurs
by either the removal of
Oxidation Reduction oxygen or the addition of
hydrogen.
Addition of oxygen Removal of oxygen

Removal of Addition of hydrogen
hydrogen


Oxidation and reduction
occur simultaneously in a
reaction: hence it is called
redox reaction.


Zinc oxide undergoes
reduction by losing oxygen to
Carbon become zinc, and carbon
undergoes oxidation by
gaining oxygen, to become
carbon monoxide.

Zinc oxide Calcium hydroxide


Interactivity

Identify oxidation and reduction.

H2S + Cl2  2HCl + S

View answer


H2S + Cl2  2HCl + S

H2S undergoes oxidation by the removal of
hydrogen. Cl2 undergoes reduction by the addition of
hydrogen.


Thermal Dissociation A compound is dissociated
into simple compounds on
heating. Since this
dissociation takes place due
to heating it is called
‘thermal dissociation’.

Thermal = By heating
Dissociation = Splitting into simple compounds


Hydrogen peroxide dissociates
on heating, to give water and
oxygen, in the presence of
In the presence of MnO2 manganese oxide.

Heat
2H2O2 2H2O + O2
MnO2
Hydrogen Water Oxygen
peroxide


Interactivity

What happens when ammonia is
heated in the presence of tungsten as
catalyst?

View answer


Ammonia dissociates into
nitrogen and hydrogen in the
presence of tungsten.

Ammonia dissociates into nitrogen and
hydrogen in the presence of tungsten.

Heat
2NH3 N2 + 3H2


Reversible and Irreversible Reactions You can compare reversible
and irreversible reactions as
S.No. Reversible reaction Irreversible reaction shown in the table.

1. The reaction can be The reaction can be started
started from either from the reactant side only.
side.

2. Forward and Only the forward reaction
backward reactions takes place.
are in equilibrium.

3. Represented by an Represented by an normal
equilibrium arrow arrow

4. The reaction is never The reaction proceeds to
complete. completion.

Next


Thermal decomposition of
phosphorus pentachloride into
phosphorus trichloride and
chlorine is a good example of a
reversible reaction.

PCl5 PCl3 + Cl2
Phosphorus pentachloride Phosphorus trichloride


Phosphorus pentachloride
dissociates into phosphorus
trichloride and chlorine in the
forward reaction

Forward reaction
PCl5  PCl3 + Cl2
Reactant Products


Phosphorus trichloride and
chlorine combine with each
other to become phosphorus
pentachloride in the backward
reaction.

Backward reaction
PCl5  PCl3 + Cl2
Product Reactants


Neutralisation between a strong
acid and strong base is an
irreversible reaction, with the
evolution of heat.

NaOH + HCl  NaCl + H2O + 13.7 kcal


Interactivity
Match the type of reaction

1 ZnCO3 Heat  ZnO + CO2 A Redox reaction
2 Mg + H2SO4  MgSO4 + H2 B Combination
reaction
3 2NaI + Cl2  2NaCl + I2 C Decomposition
reaction
4 4Na + O2  2Na2O D Single
displacement
reaction

View answer


1 ZnCO3 Heat  ZnO + CO2 C Decomposition
reaction

2 Mg + H2SO4  MgSO4 + H2 D Single
displacement
reaction

3 2NaI + Cl2  2NaCl + I2 A Redox reaction
4 4Na + O2  2Na2O B Combination
reaction


Summary

Combination In this lesson you have learnt
different types of chemical
reactions such as combination ,
Reversible Decomposition decomposition, thermal
dissociation, redox,
& neutralisation, displacement,
Thermal double displacement ,
Irreversible dissociation reversible and irreversible
reactions.
Displacement
Redox

Double
Neutralisation
displacement
Types of Reaction

Chemical reaction types_grade_10

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