UNIVERSITY OF MINNESOTA DULUTH
DEPARTMENT OF CHEMICAL ENGINEERING
ChE 3211-4211
BATCH REACTOR
OBJECTIVE
To measure the rate of saponification reaction between NaOH and ethyl acetate, using a batch
reactor, as a function of temperature and establish the rate law. Also determine the
pre-exponential factor A using the Arrhenius Equation.
INTRODUCTION
The stoichiometry of the saponification reaction between NaOH and EtOAc is :
NaOH + EtOAc → NasOAc + EtOH
REFERENCES
ChE 3611 Textbook, H.S. Fogler, "Elements of Chemical Reaction Engineering"
International Critical Tables, Vol 7.
EQUIPMENT
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9.
10.
Thermostatted bath
Conductivity meter
Stopwatch.
Reaction vessel - 250 mL jacketed beaker.
Volumetric flasks.
100 mL graduated cylinder.
Pipets of assorted sizes.
50 mL Buret.
50 mL E-flasks.
150 mL E-flask
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CHEMICALS/MATERIALS
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3.
4.
Potassium Acid Phthalate - 0.02 M
HCl - 0.02 M
NaOH - 0.02 M
EtOAc - 0.02 and 0.2 M
EXPERIMENTAL PROCEDURE
Refer to Figure 1 for a schematic of the batch apparatus. Your experiment should include the
following investigations.
For all batch experiments, use equal volumes of each reactant, to give a 200 mL total reaction
mixture volume at the start of the experiment (time = 0.0). The reaction rate should be measured
at four temperatures in the range 6C 25C. You should choose concentrations and temperatures
of reactants to give a sufficiently slow rate of reaction. The temperature of the reactor mixture
should be monitored and the temperature recorded several times during the experiment. The
suggested order of experiments is:
1. Verify the reaction is first order with respect to one of the reactants. One useful
technique is "swamping" -- that is, using a large excess of the second reactant so that its
concentration remains essentially constant during the experiment. Ten (10) times the
concentration is sufficient in this experiment. A reaction of this type may be called a
pseudo-first order reaction. This batch experiment should be run at a temperature of
about 6C.
2. Verify the reaction is second order overall. This can be done by running the
experiment as a batch reactor with equal initial concentrations of both reactants. A
minimum of three batch experiments should be run with equal concentrations of
reactants, one at the same temperature as the swamping reaction above, one at the
temperature of the domestic water supply (approximately 12C) and one at or above the
room temperature. A fourth batch experiment can be run at some intermediate
temperature if time permits.
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Figure 1. Laboratory Batch Reactor System.
The reactants should be as close to the same temperature as possible before starting the
experiment. This can be done by placing one reactant in the reaction vessel and the other reactant
in the constant temperature bath and letting them reach the same temperature before mixing them
together. If reactions proceed too quickly, the experiments should be repeated with half the initial
concentrations. If you do this, you will also need to reduce the concentration of the other reagents
used in the analysis procedure by half.
Ask the Lab Services Coordinator for information on adjusting the temperature of the constant
temperature baths.
ANALYSIS PROCEDURE
In order to monitor the rate of the reaction in these experiments, it is necessary to determine
the amount of unreacted NaOH at appropriate time intervals. The reaction mixture can be
monitored by a titration method.
Titration Method
A small sample is collected from the reaction vessel and quenched (reaction terminated) in a
known volume and concentration of HCl. The excess HCl is titrated with NaOH. From this
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titration the amount of unreacted NaOH can be determined and used in the determination of the
rate constant. A self-filling 10 mL buret is used to titrate the samples. You are encouraged to
practice using the buret - you should be able to obtain titers within  0.02 mL on the same solution.
Your ability to titrate will be reflected in the quality of your data! The 10 mL buret is very
delicate and should be treated with great care.
The steps needed to accomplish this are listed below:
1. The sodium hydroxide used in the experiment is standardized using the acidimetric
standard (potassium hydrogen phthalate [KHP]) available on the bench. Pipet 5 mL of
KHP into a 50 mL erlenmeyer flask. Titrate the KHP with the NaOH using the
supplied burette until the phenolphthalein end point (pink) appears (run a minimum of
three titrations).
2. The concentration of HCl is determined using the NaOH standardized above. Pipet 5
mL of HCl into a 50 mL erlenmeyer flask. Titrate the HCl with the NaOH using the
supplied burette until the phenolphthalein end point (pink) appears (run a minimum of
three titrations).
3. 5 mL of the HCl is pipetted into each of several 50 mL erlenmeyer flasks (E-flasks)
before the experiment begins.
4. Samples should be collected from the reactor vessel using a 5 mL transfer pipet or a 5
mL Finnpipet at appropriate time intervals to monitor the rate of reaction. At the start
of the reaction samples should be collected at short time intervals. The time interval
can be increased as the reaction proceeds. No more than 6 or 7 samples should be
collected during the run. The 5 mL sample should be discharged into the 50 mL
E-flask containing 5 mL of HCl. The time of collection shall be taken when one-half of
the sample has been discharged from the pipet into the E-flask.
5. The sample is titrated with the standardized base and the volume recorded.
It is essential for the reactants to be as close to the same temperature as the reaction
temperature, for the reactants to be mixed together rapidly, and the stopwatch started
simultaneously.
SAFETY NOTES
1. Before starting the experiment, review the Material Safety Data Sheets (MSDS) on
NaOH, HCl, and EtOAc. The sheets can be found in the MSDS notebook located in
the laboratory.
2. Personal protective equipment shall include goggles or a face shield. Eye glasses with
side shields will not be sufficient for this experiment. Disposable nitrile gloves should
be worn when handling NaOH solutions.
3. A small amount of NaOH spilled on the outside of glassware and/or equipment can
cause the glassware and equipment to be extremely slippery when wet. Be careful.
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WASTE DISPOSAL PROCEDURES
Collect all waste chemical solutions in the container marked with "BATCH waste solution"
and your lab period. At the end of each lab period or the end of the experiment, add sufficient
base (NaOH) to yield a phenolphthalein end point (pink) that does not disappear overnight. This
indicates the reaction has gone to completion and the waste can be disposed down the drain. Why?
Do not add too much base as the pH has to be less than 10 before it can be disposed down the drain.
Once the phenolphthalein end point stays pink and the pH is less than 10, contact the lab services
coordinator.
02/2013
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Department of Chemical Engineering
Stockroom Checkout slip
Batch Reactor Experiment
ChE 4211
Name:
Date:
(print name)
Lab No.:Lab 1
Lab No.:
Tuesday
Lab 3
12:00 - 4:50 PM
Lab 2: Thursday
12:00 - 4:50 PM
Tuesday and Thursday morning (9:30 - 11:50 AM)
(circle one)
Equipment
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In
Equipment
12-50 mL E-flasks
Stopwatch
100 mL grad. cylinder
1-pipet bulbs
Digital thermometer
2-150 mL beakers
10 mL grad. pipet
250 mL erlenmeyer flask
1-5 mL transfer pipet
1-clamp
1-Finnpipette (1-5 mL)
Name:
(Signature)
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Out
In