reversible reaction

Marwan Bin Yaacob @ Salleh
MRSM Parit

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

0021 Reversible reaction
Equilibrium
03 Changing equilibrium

• Understand the reversible reaction
• Concept of equilibrium for reversible reaction
• The effect of changing reaction condition to

equilibrium

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Is this reaction is
reversible?
Why is that?

Combustion reaction

Is it reversible 01 Why?02 We cannot get back
reaction?
the reactant that we
No. used

03 How do we classify
this reaction?
Irreversible

reaction

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Heating of
IshytdhriastreedaCcutSioOn4 is

reversible?
Why is that?

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Heating of hydrated CuSO4

• The most common example for reversible reaction

• The blue hydrated copper(II) sulphate will turn into white anhydrous
copper(II) sulphate

• Hydrated copper(II) sulphate can be obtained by adding few drops of
water

• The equation for the reaction is given below

CuSO4.5H20 CuSO4 + 5H2O

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

What is reversible reaction?

• The reaction that can proceed both

direction, forward and backward.

• The sign “ is used in the equation
to indicate the reaction is reversible.

Other example

+NH3 (g) HCl (g) NH4Cl (s)

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Irreversible Classify the following reaction: Reversible

Reaction Reversible/
Irreversible
3H2(g) + N2(g) → 2NH3(g)
NH4Cl(s) → NH3(g) + HCl(g)
2H2(g) + O2(g) → 2H2O(l)
CuSO4 + 5H2O → CuSO4.5H2O

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Chemical Equilibria and Le
Chatelier’s Principle

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Haber Process

N2 + 3H2 2NH3

• The reaction is reversible
• As the reaction proceeds, some of
ammonia formed breaks down into
hydrogen gas and nitrogen gas
• At certain point of the reaction, rate
of forward and backward reaction is
equal.
• The concentration of reactant and
product remains constant.
• This condition is known as
EQUILIBRIUM

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

01 At equilibrium 03

Rate of reaction 02 Condition

Rate of forward Concentration of The reaction
and backward reactant and product is carried out

reaction is the Concentration of in a closed
same reactant and system

product remains
constant

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Quick test

What is meant by the term equilibrium?

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

You could enter a subtitle here
if you need it

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

“When a change is made to the
condition of a system in dynamic
equilibrium, the system moves so to

oppose that change”

N2(g) + 3H2(g) 2NH3(g)

Factors that affect equilibrium

Condition Effect

Temperature Increasing the temperature shifts the
equilibrium towards endothermic reaction
Concentration (absorb heat) and vice versa

Increasing the concentration of a substance
shifts the equilibrium in the direction that
produces less of that substance.

Pressure Increasing the pressure shifts the
equilibrium to the side that produces less
number of mole/molecule of gas

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Effect of temperature

2SO2(g) + O2(g) 2SO3(g) ∆H = -197kJ/mol

What will happen to the yield and equilibrium if temperature is increased?

● Forward reaction is exothermic.
● If temperature is increased, the equilibrium will move to the left
● Yield will decrease
● This is due the forward reaction is exothermic while backward reaction is

endothermic. Increasing temperature favour backward reaction as it is
endothermic and hence less yield (product) is produced

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Effect of Pressure

2SO2(g) + O2(g) 2SO3(g) ∆H = -197kJ/mol

What will happen to the yield and equilibrium if pressure is increased?

● Forward reaction has smaller number of mole
● If pressure is increased, the equilibrium will move to the right.
● Yield will increase
● This is due the forward reaction has smaller number of mole. Increasing

pressure favour side with smaller number of molecules.

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Effect of temperature

BiCl3(aq) + H2O (l) BiOCl(s) + 2HCl(aq)

What will happen to the yield and equilibrium if concentration is increased?

● If water is added, there is more water in the reactant
● The equilibrium will move to the right to use (decrease) the water added.
● Yield will will increase.

● However, if more HCl is added, equilibrium will move to the left
and produce more BiCl3 and hence reduce the yield

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Bitesize Quiz

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Bitesize Quiz

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

Bitesize Quiz

Marwan Bin Yaacob @ Salleh || MRSM Parit 2020

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Marwan Bin Yaacob @ Salleh || MRSM Parit 2020