This experiment is based on the experimental demonstration of Determine the velocity constant of alkaline hydrolysis of ethyl acetate by conductometric method. The presentation is made for the chemistry undergraduate students of Mumbai University.

1. Determine the velocity constant of
alkaline hydrolysis of ethyl acetate by
conductometric method
Dr. Singare
Associate Professor
Department of Chemistry,
N.M Institute of Science, Bhavan’s College,
Andheri (West), Mumbai 400 058

2. Understanding the basic concept
• Conductance of a solution gives an indication of how easily the charge particles can migrate in a solution
(measured in Siemens, S).
• Conductivity is the conductance (S) of a solution measured between the two electrodes separated by a
distance of 1 cm, measured in Siemens per centimeter (S/cm).
• Frequently conductivity is expressed in the unit of micro Siemens/ cm (μS/cm) or milli Siemens/cm
(mS/cm).
• 1mS = 1000 μS
• Conductivity of the solution is measured by using a conductivity cell.
• The conductivity cell consist of platinized platinum electrode separated by a distance of l =1 cm.
• The surface area of cross section of platinized platinum electrode a = 1cm2.
• Therefore the cell constant = l/a = 1cm/1cm2 = 1cm-1.
• During the conductivity measurement, when an alternating voltage is applied to one of the platinum
electrodes there will be the migration of ions in the solution towards the electrodes.
• Greater the migration of ions in the solution, greater will be the current flowing between the platinum
electrodes.
• The current produced in the conductivity cell is measured by the conductivity meter
• On the basis of Ohm's law, the conductivity meter calculate first the conductance and then the conductivity
of the solution.

3. • For all the conductometric experiments, conductivity water is used.
• Conductivity water is that which is having a conductivity of less than 0.043 × 10–6 S cm–1
• It is prepared by distilling the tap water and passing the distilled water thus obtained
through the cation and anion exchange columns.
• Distilled water conducts electricity, whereas conductivity water does not.
• The conductivity water which is obtained by ion exchange process usually has the basic
pH.

4. Requirements:
 0.01 N NaOH solution,
 0.01 N Sodium acetate (CH3COONa),
 ethyl acetate,
 Conductivity water,
 conductivity meter with conductivity cell,
 Stop watch

5. Reaction
CH3COOC2H5 + NaOH  CH3COONa + C2H5OH
(ethyl acetate) + (sodium hydroxide)  (sodium acetate) + (ethyl alcohol)
Procedure:
1. To determine the kinetics of the above reaction by conductometric method, measure the conductance in milli Siemens [mS]
of 100 mL of 0.01 N NaOH solution and record the conductance as C0 i.e. conductance at Zero time.
2. Similarly measure the conductance in milli Siemens [mS] of 100 mL of 0.01 N Sodium acetate (CH3COONa) and record the
conductance as C∞ i.e. conductance at infinite time.
3. Take 2 beakers of 100mL capacity. Beaker 1: 5 mL of ethyl acetate + 25 mL of distilled water.
Beaker 2: 20 mL of 0.05 N NaOH + 50 mL of distilled water.
4. Keep both the beakers in water bath for 5 min to attain the room temperature.
5. At known time mix solution of beaker 1 to solution of beaker 2 and immediately start the stop watch.
6. This mixture is called reaction mixture.
7. Immerse the conductivity cell in the reaction mixture.
8. Keep on stirring the reaction mixture.
9. Record the conductance (Ct)in milli Siemens [mS] of the reaction mixture at an interval of every 2 min for initial 10
minutes and thereafter measure the conductance (Ct) of the reaction mixture at an interval of every 5 minutes till 30
minutes.

6. Time
(min)
Time
(Sec)
Conductance
(mS)
Ct
C0 - Ct Ct - C∞ C0 – Ct / Ct - C∞
k =
1
0.01𝑥 𝑡(𝑠𝑒𝑐) (
𝐶0
−𝐶𝑡
Ct − C∞
)
mol-1cm3sec-1
0 0
4.31
(C0=Ct)
0.00 3.51 0.000 0
2 120 4.27 0.04 3.47 0.012 0.0096061
4 240 4.15 0.16 3.35 0.048 0.0199005
6 360 4.09 0.22 3.29 0.067 0.0185748
8 480 4.05 0.26 3.25 0.080 0.0166667
10 600 4.01 0.30 3.21 0.093 0.0155763
15 900 3.96 0.35 3.16 0.111 0.0123066
20 1200 3.92 0.39 3.12 0.125 0.0104167
25 1500 3.90 0.41 3.10 0.132 0.0088172
30 1800 3.85 0.46 3.05 0.151 0.0083789
∞ ∞ 0.80
(C∞=Ct)
3.51 0.00 - -
Mean k 0.012 mol-1cm3sec-1
Note: The conductance values to be recorded in milli Siemens (mS) only. The values obtained in micro Siemens (µS) to be
converted to mS. 1mS = 1000 μS

7. Theory
• The reaction studied in the present experiment is
CH3COOC2H5 + NaOH  CH3COONa + C2H5OH
(ethyl acetate) + (sodium hydroxide)  (sodium acetate) + (ethyl alcohol)
• Initial when the reaction has not started, the conductance is because of the reactant NaOH
present in the solution.
• Since NaOH dissociate to give lighter ions (Na+ & OH-) which can migrate fast, the initial
conductance Co is maximum. In the present experiment Co is 4.31mS.
• As the time increases, the reaction proceed and NaOH is getting consumed. As a result the
conductance of reaction mixture decreases with time.
• At time infinite (∞) time , when all the reactants are completely consumed, the conductance is
because of the product sodium acetate (CH3COONa) which is formed during the reaction.
• Sodium acetate (CH3COONa) dissociate to give ions (Na+ & CH3COO-).
• Because of bulky acetate (CH3COO- ) ions which migrates slowly, the conductance of the solution at infinite
time (C∞)will be minimum. In the present experiment C∞ is 0.80 mS.

8. • k (by calculations)
=
1
0.01𝑥 𝑡(𝑠𝑒𝑐)
(
𝐶0
−𝐶𝑡
Ct − C∞
)
• Slope = 0.00018
• k (by graph) = slope /0.01
• k (by graph) = 0.018 mol-1cm3sec-1
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090
0 100 200 300 400 500 600
C0
–
Ct
/
Ct
-
C∞
Time (sec)

9. Results:
k (by calculation) = 0.012 mol-1cm3sec-1
k (by graph) = 0.018 mol-1cm3sec-1