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12C04

Chemical Kinetics

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Kinetics

Kinesis

Movement

Chemical Kinetics

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12C04.1

Rate of Reaction

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12C04.1 Rate of Reaction

Learning objectives

Rate of reaction

Average and Instantaneous rate of reaction

Expression for rate of a reaction

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12C04.1

CV 1

Rate of Reaction

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Rate of the Reaction

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Consider a reaction:

R

P

Time

Rate of the Reaction

Conc.

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Consider a reaction:

R

P

Rate of the Reaction

As concentration of reactant is decreasing, so multiplied by -1 to make rate of reaction a positive quantity

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Types of reaction

Fast reaction

Moderate reaction

Slow reaction

Rate of the Reaction

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Fast Reaction

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Moderate Reaction

Time period is not too small or too large

Examples: Inversion of cane sugar, Hydrolysis of starch

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Slow Reaction

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12C04.1

CV 2

Average and Instantaneous Rate of Reaction

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Average Rate of Reaction

Time

Conc.

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Instantaneous Rate of Reaction

0

10

20

30

40

50

20

40

60

80

100

120

It is determined graphically by drawing a tangent at time t on either of curves for concentration of R and P versus t and calculating it’ s slope.

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12C04.1

PSV 1

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12C04.1

CV 3

Expression for Rate of Reaction

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Expression for Rate for Reaction

Stoichiometric coefficients of reactant or products are not equal

1 mol consumed

3 mol consumed

2 mol produced

Rate of Reaction

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Example 1:

Example 2:

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12C04.1

PSV 2

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12C04.1 Rate of reaction

Reference questions

NCERT Intext questions : 4.1, 4.2

Workbook questions : 4, 10

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12C04.2

Rate Law, Order and Molecularity

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12C04.2 Rate Law, Order and Molecularity

Learning objectives

Rate law

Units of rate constant

Elementary and complex reaction

Molecularity of reaction

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12C04.2

CV 1

Rate Law

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Rate Law

Rate Constant

Reaction

Temperature

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Order of Reaction

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Order can be determined experimentally not by balanced equation

Order of Reaction

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Q. The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y ?

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Q. The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y ?

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12C04.2

PSV 1

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0.2	0.2	0.4
0.3	0.1	0.05

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12C04.2

CV 2

Unit of Rate Constant

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Unit of Rate Constant

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Unit of Rate Constant

Order

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12C04.2

PSV 2

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Sol.

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12C04.2

CV 3

Elementary and Complex Reaction

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Reaction which takes place in single step.

Elementary Reaction

For elementary reaction,

Order of reaction = Sum of stoichiometric coefficients of reactants.

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Complex Reaction

Each step is called elementary reaction

Overall rate of complex reaction is determined by slowest step

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Molecularity of Reaction

Unimolecular

Reaction in which only one molecule takes part

Example:

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Bimolecular

Reaction in which 2 molecules take part in reaction

Example:

Molecularity of Reaction

Trimolecular

Reaction in which 3 molecules take part in the reaction

Example:

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Why molecularity of three is very rare??

Molecularity of Reaction

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12C04.2 Rate Law, Order and Molecularity

Reference questions

NCERT Exercise questions : 4.1, 4.2, 4.4, 4.6, 4.11, 4.12

Workbook questions : 1, 2, 3, 5

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12C04.3

Integrated Rate Law

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12C04.3 Integrated Rate Law

Learning Objectives

Integrated rate equation

First order reaction

Half life for zero order and first order

Pseudo first order reaction

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12C04.3

CV 1

Integrated Rate Equation

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Integrated Rate Equation

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Integrated Rate Equation

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Zero Order Reaction

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Graphical representation of Zero Order Reaction

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12C04.3

CV 2

First Order Reaction

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First Order Reaction

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Graphical representation of First Order Reaction

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First Order Reaction for Gaseous Phase Reactions

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12C04.3

PSV 1

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12C04.3

CV 3

Half Life

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Half Life is equal to 3.1 minutes

Half Life

Radioactivity	Time(min)

8	0

4	3.1

2	6.2

1	9.3

0.5	12.4

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Half Life for Zero Order Reaction

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Half Life for First Order Reaction

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12C04.3

PSV 2

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12C04.3

CV 4

Pseudo First Order Reaction

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Pseudo First Order Reaction

The type of reaction which obey first order rate law although it has higher molecularity for the reaction.

At t = 0 0.1 mol 50 mol 0 mol 0 mol

At t = t 0 mol 49.9 mol 0.1 mol 0.1 mol

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12C04.3 Integrated Rate Law

Reference Questions

NCERT Exercise questions : 4.3, 4.8, 4.13, 4.14. 4.15, 4.16, 4.17, 4.18, 4.21, 4.24

Workbook questions : 16, 17, 20

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12C04.4

Arrhenius Equation

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12C04.4 Arrhenius Equation

Learning objectives

Arrhenius equation

Mathematical interpretation of Arrhenius equation

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12C04.4

CV 1

Arrhenius Equation

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Observation of Van’t Hoff

Temperature coefficient

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Arrhenius Equation

A mathematical relation between rate constant and temperature.

Rate Constant

Arrhenius

Factor

or

Pre-exponential

Factor

Temperature

Gas

Constant

Activation Energy

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Activation Energy

Reactant

Activated complex

Product

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Activation Energy

Activated Complex

Reaction coordinate

Energy

Minimum energy which must be provided to a chemical system with potential reactants to undergo reaction and form products.

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Maxwell- Boltzmann Distribution

Kinetic Energy

Fraction of molecules

More number of molecules

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12C04.4

PSV 1

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12C04.4

CV 2

Mathematical Interpretation

of

Arrhenius Equation

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Mathematical Interpretation of Arrhenius Equation

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Mathematical Interpretation of Arrhenius Equation

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12C04.4

PSV 2

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12C04.4 Arrhenius Equation

Reference Questions

NCERT Exercise questions : 4.22, 4.26. 4.27, 4.28, 4.30

Workbook questions : 18, 19

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12C04.5

Collision Theory

and

Effect of Catalyst

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12C04.5 Collision Theory and Effect of Catalyst

Learning Objectives

Collision Theory

Effect of Catalyst

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12C04.5

CV 1

Collision Theory

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Collision Theory for Rate of Reaction

Collision Theory

Molecules Hard Spheres

Effective Collision

Proper orientation

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Collision Theory for Rate of Reaction

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Collision Theory for Rate of Reaction

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12C04.5

CV 2

Effect of Catalyst

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Effect of Catalyst

Activated complex

Reaction Coordinate

Energy

New activated complex

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Effect of Catalyst

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12C04.5 Collision Theory and Effect of Catalyst

Reference Questions

NCERT Intext questions : 4.9

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12C04.4

PSV 2

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