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# CBSE Chemistry Project

On Chemical Kinetics

By Badree (XII-B)

NEW DELHI-17

## The project involves the aim to understand the order of

reaction of methyl ethanoate's hydrolysis (catalysed by
acid).

PROJECT ON
CHEMICAL
KINETICS:
Acid
catalysed
hydrolysis
of ester.

Contents
1. Certificate
2. Acknowledgement
3. Objective
4. Theory I (introduction)
5. Theory II (factors affecting
rate of
reaction)
6. Materials Required
7. Experimental Procedure
8. Observation
9. Calculations
10. Result and Conclusion
11. Precautions

12. Bibliography

CERTIFICATE
This is to certify that the Project titled
'Chemical Kinetics: Acid catalysed
hydrolysis of ester'was completed
under my guidance and supervision by
Badree, Roll No. ________ a student of XIIB, New Green Field School,Saket within
the stipulated time as prescribed by the
CBSE.
Mr.Harold Perera, Chemistry Teacher
New Green Field School, Saket, New Delhi.

ACKNOWLEDGEME
NT
I gratefully acknowledge my sincere
thanks to our
respected chemistry teacher Mr.Harold
Perera for
helping me decide on the project of my
choice and his remarkable, valuable
guidance and supervision
throughout the project work.

OBJECTIVE
To understand the hydrolysis of methyl
ethanoate catalysed by HCL and
determine the order of the reaction and
rate constant by using the values
obtained by titrating it against a standar
base, NaOh.
by (i) Graphically,
(ii)Mathematically

THEORY:

INTRODUCTION
CHEMICAL KINETICS
Chemical kinetics deals with the experimental
determination of reaction rates from which rate laws and
rate constants are derived. Relatively simple rate laws
exist for zero-order reactions (because reaction rates are
independent of concentration), first-order reactions, and
second-order reactions can be derived for others. In
consecutive reactions, the rate-determining step often
determines the kinetics. In consecutive first-order
reactions, a steady state approximation can simplify the
rate law.

FACTORS AFFECTING
REACTION RATE
NATURE

OF THE REACTANTS

## Depending upon what substances are reacting, the

reaction rate varies. Acid/base reactions, the formation of
salts, and ion exchange are fast reactions. When covalent
bond formation takes place between the molecules and
when large molecules are formed, the reactions tend to
be very slow. Nature and strength of bonds in reactant
molecules greatly influence the rate of its transformation
into products.

PHYSICAL

STATE

## The physical state (solid, liquid, or gas) is also an

important factor of the rate of change. When reactants
are in the same phase, as in aqueous solution, thermal
motion brings them into contact. But, when they are in
different phases, the reaction is limited to the interface
between the reactants. For example reaction can occur
only at their area of contact; in the case of a liquid and a
gas, at the surface of the liquid. Vigorous shaking/stirring
may be needed to complete the reaction. This means that
the more finely divided a solid or liquid reactant the
greater its surface area per unit volume and the more
contact it makes with the other reactant, thus the faster
the reaction.

PRESSURE
Increasing the pressure in a gaseous reaction will
increase the number of collisions between reactants,
increasing the rate of reaction

CONCENTRATION

## The reactions are due to collisions of reactant species.

The frequency with which they collide depends upon their
concentrations.The more crowded the molecules are
(high conc.), the more likely they are to collide and react.
Thus, an increase in the concentrations of the reactants
will result in the corresponding increase in the reaction
rate,vice versa. For example, combustion that occurs in
air (21% oxygen) will occur more rapidly in pure oxygen.

FREE

ENERGY

## The free energy change (G) of a reaction determines

whether a chemical change will take place. It is possible
to make predictions about reaction rate constants for a
reaction from free-energy relationships.

## Although,kinetics describes how fast the reaction is. A

reaction can be very exothermic and have a very positive
entropy change but will not happen in practice if the
reaction is too slow. Also, if a reactant can produce two
different products, the thermodynamically most stable
one will in (generally) form.

TEMPERATURE

## Temperature has a major effect on the rate of a chemical

reaction. Molecules at a higher temperature have more
thermal energy.This makes collisions frequent and the
proportion of reactant molecules with sufficient energy to
react (energy greater than activation energy: E > Ea) is
significantly higher as explained by the Maxwell
Boltzmann distribution of molecular energies.

EQUILIBRIUM

## It determines the extent to which reactions occur. In a

reversible reaction, chemical equilibrium is reached when
the rates of the forward and reverse reactions are equal
and the concentrations of the reactants and products no
longer change.Component concentrations can oscillate
for a long time before finally attaining the equilibrium .

CATALYSTS

## A catalyst is a substance that accelerates the rate of a

chemical reaction (or lowers activation energy) but
remains chemically unchanged afterwards. The catalyst
increases rate reaction by providing a different reaction
mechanism to occur with a lower activation energy.

MATERIALS AND
EQUIPMENT REQUIRED:
CHEMICALS

Methyl acetate
Hcl
Naoh
Oxalic Acid
Phenolphthalein

APPARATUS

Conical flask
Thermostat bottles
Reagent
Burette
Pipette
Ice

PROCEDURE
Step I: Standardization of NaOH using standard Oxalic
acid(0.1N)
1. 10ml of given 0.1N standard Oxalic acid is pipetted out
into a 100ml
conical flask.
2. This solution is titrated against the given unknown
concentration of
NaOH using phenolphthalein indicator until the end
point is colorless
to pale pink.
3. Tabulate the values and repeat the titration for
concurrent readings
and determine the unknown concentration of supplied
NaOH
solution

## 1. 2 ml of given HCl is pipetted out into a 100ml conical

flask.
2. This solution is titrated against the NaOH using
phenolphthalein
indicator until the end point is colorless to pale pink.
3. Tabulate the values and repeat the titration for
concurrent readings
and determine the unknown concentration of supplied
HCl solution.

## 1. 100 ml of given HCl (whose strenght is determined in

step II) solution
is taken in a stoppered reagent bottle.
2. 5 ml of methyl acetate solution is added to the HCl
solution. Note
the time when half the methyl acetate solution is
added. The mixture
is shaken well.
3.Pipette out 5 ml of the reaction mixture and discharge it
into 50 ml of
ice cold water kept in a conical flask.
4.Titrate the reaction mixture against NaOH solution,
using
phenolphthalein as indicator. This titre value
corresponds to Vo .
Steps 3 and 4 are repeated at intervals of 5, 10, 15, 20,
30, 45, 60
minutes. Each titre value corresponds to Vt .
5. The remaining solution is taken in a stoppered conical
flask and
heated to 60oC, and kept at this temperature for 5
minutes.
6.The solution is allowed to cool to room temperature.
Repeat Steps 3 and 4. This titre value corresponds to
V till
concurrent values are obtained.

## 7. Plot a graph of log (V -Vt ) versus time (t) and

determine the
slope.
8. Report the theoretical and graphical value of rate
constant (k1).

OBSERVATIONS
Table corresponding to step I
Standardization of NaOH using standard Oxalic acid(0.1N)
S.No.

Vol.(oxalic acid)
in ml

Burette (initial)
in ml

1.
2.
3.

Burette(final)
in ml

Volume of NaOh
in ml

## Standardization of HCl using NaOH solution

S.No.

Vol.(HCl)
in ml

Burette (initial)
in ml

Burette(final)
in ml

Volume of NaOh
in ml

1.
2.
3.

## Table corresponding to step III

Determination of Rate Constant
S.No.

time
(min.)

## Volume Burette Burette Volume V-Vt

of sol. in (Initial) (Final)
of
ml
in ml
in ml
NaOh
in ml

1.
2.
3.
4.

CALCULATIONS
TABLE I
(HCOO)2N1 V1 = N2 V2

(NaOH)

## Concentration of NaOH, N2 = _______________

TABLEII
(NaOH) N2V2 = N3 V3 (HCl)

## Concentration of HCl, N3 = ______________

TABLE III
CALCULATING THE RATE CONSTANT
(I) MATHEMATICALLY:
In the presence of an acid, this reaction should be of
second order, since two molecules are reacting. But, it is
found to be first order. This may be explained in the
following way :
The rate of the reaction is given by
dx / dt = k[CH3COOCH3] [ H2O ] ,
where k is the rate constant.
Since water is present in large excess, its active mass
(molar concentration) virtually remains constant during
the course of the reaction. Therefore, its active mass gets
included in the constant, and the above equation
reduces to :
dx / dt = k1 [CH3COOCH3]
Thus, the rate of the reaction is determined by one
concentration term only (that is, by a single power of the
concentration term only).
Hence, the reaction is first order. Such reactions are also
called pseudo first order reactions.
K1=2.303/t(logV-Vo/V-Vt)
S.N K1

o.
1.
2.
3.
4.

(II)GRAPHICALLY
In order to determine the rate law for a reaction from a
set of data consisting of concentration (or the values of
some function of concentration) versus time, make three
graphs.
[A] versus t (linear for a zero order reaction)
ln [A] versus t (linear for a 1st order reaction)
1 / [A] versus t (linear for a 2nd order reaction)
ZERO ORDER

FIRST ORDER

SECOND ORDER

## Therefore it is easy to infer the order of a reaction

graphically
Hence the plots for concentration of ester are:

RESULT &CONCLUSION
Hence the acid catalysed hydrolysis is a (pseudo) first
order reaction, verified graphically and mathematically
whose rate constant is :

PRECAUTIONS
1.Ethyl acetate is highly flammable. Harmful if swallowed
in quantity.
Vapours may cause drowsiness.
2.Hydrochloric acid is corrosive. In the event of skin contact, wash well
with water.
3.The dilute sodium hydroxide solution caustic,and one should not
handle them with hands
4.When diluting the hydrochloric acid, remember to add the
concentrated acid to water to avoid splattering. Take care in
handling the container as the dilution will generate heat.
5.Dissolving of sodium hydroxide generates heat. Take care in handling
the dilution container.
6. All solutions in this experiment should be disposed of in the proper
waste containers as provided in the laboratory.

BIBLIOGRAPHY
1.www. chem-guide.blogspot.com
2.www.wikipedia.org
3.NCERT PART I
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