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Half Life

The document outlines an experiment to determine the reaction rate constant and half-life of ester during acid hydrolysis, specifically using ethyl acetate and hydrochloric acid. It describes the necessary materials, theoretical background, and detailed procedure for conducting the experiment at various temperatures. The results will allow for the calculation of the rate constant and half-life using the provided equations.

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16 views3 pages

Half Life

The document outlines an experiment to determine the reaction rate constant and half-life of ester during acid hydrolysis, specifically using ethyl acetate and hydrochloric acid. It describes the necessary materials, theoretical background, and detailed procedure for conducting the experiment at various temperatures. The results will allow for the calculation of the rate constant and half-life using the provided equations.

Uploaded by

vvb
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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DETERMINATION OF REACTION RATE CONSTANT AND HALF LIFE

AIM

To determine the reaction rate constant and half-life of ester subjected to acid hydrolysis.

REQUIREMENTS:
Conical flask, pipette, water bath, burette, cold water, Sodium hydroxide hydrochloric
acid, ethyl acetate and phenolphthalein indicator.

THEORY:

The reaction rate for a reactant or product in a particular reaction is intuitively defined as
how fast a reaction takes place. The rate of reaction is defined as the change in the
number of molecules of reacting species per unit volume per unit time. It is also defined
to be proportional to the concentration of reacting species raised to a certain power called
the order of reaction. It is usually taken as the rate at which the reactant disappear or the
rate at which the product is formed. The rate at which the reactant ‘a’ is disappearing is
proportional to its concentration at any instance,

Rate (r) = k (a - x)

Where k = rate constant

Hydrolysis is a chemical decomposition involving breaking of a bond and the addition of


elements of water. In this hydrolysis of ester (ethyl acetate) with an alkali (sodium
hydroxide), HCl was used as catalyst to accelerate it. The fact that this is a first order
reaction is established by substituting the results in the first order rate expression;
The hydrolysis of an ester such as ethyl acetate in the presence of a mineral acid gives
acetic acid and ethyl alcohol.

The value of rate constant, K in this case, x= Vt – Vo and a =Vα –Vo

K=2.303 log (Vα – Vo)


t (Vα –Vt)

Where, Vo = initial titre value

Vα= final titre value at the end of the experiment and

Vt = titre value at the various time intervals chosen

As the hydrolysis proceeds, there will be proportional increase in the concentration of


acetic acid formed. This experiment involves determination of specific rate constant and
half-life of a reaction undergoing at different temperatures.

PROCEDURE:

Mix 5ml of ethyl acetate with 100ml of 0.1Nhydrochloric acid taken in a conical flask
and maintain at a temperature of 40°C.Withdraw 10ml of aliquot of the reaction mixture
at regular intervals (0, 15, 30, 45,60,75,90,105 and 120mins).Transfer each reaction
mixture into 30ml of ice cold water and titrate against 0.1N Sodium hydroxide using
phenolphthalein as indicator. Titrate each reaction mixture immediately after transferring
into the ice cold water and mixing with the indicator. Repeat the experiment in the same
way but maintaining the temperature at 50 °C, 60°C and 70°C.Calculate the k values from
the data obtained at each of the above temperatures and determine its corresponding half-
life.

t1/2 = 0.693/K

REPORT

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