Experiment 7 (1).pptx
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Experiment 7: Saponification Kinetics of Ethyl Acetate
Group D
Objectives
• Determine kinetics of saponification of ethyl acetate via initial slope method
• Calculate conversion of sodium hydroxide
Citation: [1]
Saponification
• Normally converts an ester to a soap• Strong bases can be used to break ester
linkage
Citation: [1], [3], [4]
OH- Na+
Ethyl Acetate Sodium Hydroxide
Reaction Rates
• Homogeneous reaction rates
• For consumption of sodium hydroxide in saponification reaction
• Through experimentation find k, x, and y• Not an elementary reaction
Citation: [2]
Experimental Methods
• Combine sodium hydroxide with ethyl acetate and water for reaction mixture
• Track NaOH consumption with conductivity meter
• Conductivity of solution
Experimental Methods
• Two different sets of experiments to determine effect of sodium hydroxide and ethyl acetate
• Ran three trials of each experiment
Experiment NaOH (M) EtAc (M) NaOH (mL) EtAc (mL) Water (mL)Aa 0.1 0.1 8 16 56Ab 0.05 0.1 4 16 60Ac 0.025 0.1 2 16 62Ba 0.1 0.3 8 48 24Bb 0.05 0.3 4 48 28Bc 0.025 0.3 2 48 30
Table 1 Amount of sodium hydroxide and ethyl acetate added for each trial.
Experimental Methods
• Calibrated conductivity probe each day• Began by mixing sodium hydroxide and water• Added ethyl acetate, and let stir until
conductivity leveled
Time
Cond
uctiv
ity
0 100 200 300 400 500 600 700 8000
0.02
0.04
0.06
0.08
0.1
0.12
Time (s)
Conc
entr
ation
of N
aOH
(mol
/L)
Results: Initial Rates
• Calculate approximate initial reaction rate by taking a linear regression of the first 20 data points• Use the ratios of initial rates and initial concentrations to find the exponents of the rate equation• Use the initial rates, concentrations, and exponents to find the rate constant
Experiment Aa1: Concentration of NaOH vs. Time with Initial Rate
Experiment Aa1: Initial Rate Derivation
34 36 38 40 42 44 460.0920
0.0940
0.0960
0.0980
0.1000
0.1020
0.1040
0.1060
0.1080
0.1100
f(x) = − 0.00104941529631037 x + 0.144467969123688R² = 0.987068319792724
Time (s)
Conc
entr
ation
of N
aOH
(mol
/L)
Results: Rate Equation
• Check the validity of our rate equation by plotting it against the experimental reaction rate• Checking it at only one set of concentrations won’t be enough…
Experiment Bb1: Reaction Rate of NaOH vs. Concentration of NaOH
0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600
-0.0005
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
Concentration of NaOH (mol/L)
Rate
(mol
/L s)
[EtAc] = 0.3 M [EtAc] = 0.1 M[NaOH]
0.100 M
0.050 M
0.025 M
0.0000 0.0200 0.0400 0.0600 0.0800 0.1000 0.1200-0.0005
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
0.0035
0.0040
0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600-0.0005
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0000 0.0050 0.0100 0.0150 0.0200 0.0250-0.0002
0.0000
0.0002
0.0004
0.0006
0.0008
0.0010
0 0.02 0.04 0.06 0.08 0.1 0.12-0.0005
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0000 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600-0.0005
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
00.002
0.0040.006
0.0080.01
0.0120.014
0.0160.018
-0.0002
0
0.0002
0.000400000000000001
0.000600000000000001
0.000800000000000001
0.001
Results: Conversion
• According to Le Chatelier's principle, we expect the excess EtAc in experiments Ab, Ac, Bb, and Bc to drive the equilibrium towards higher conversion• We only see this trend in experiments Aa, Ab, and Ac (on left), but the differences between conversions are not significant
Experiments Aa, Ab, and Ac: Conversion of NaOH vs. Concentration of NaOH
Experiments Ba, Bb, and Bc: Conversion of NaOH vs. Concentration of NaOH
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.1199.80%
99.85%
99.90%
99.95%
100.00%
100.05%
Initial Concentration of NaOH (mol/L)
Conv
ersio
n of
NaO
H (%
)
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.1199.80%
99.85%
99.90%
99.95%
100.00%
100.05%
Initial Concentration of NaOH (mol/L)
Conv
ersio
n of
NaO
H (%
)
Discussion – Results
• Addition of Sodium Hydroxide and Ethyl Acetate at different concentrations– Determine the conversion of NaOH – Determine the rate equation
• Found the rate equation with confidence intervals to be :
Discussion – Error and Suggestions
• Software would stop after a period of time– Hit “Ctrl + T” to extend the time so that it doesn’t stop during your
run– If it stops – suggest to repeat that part of the experiment
• Contamination in water– Wash out mixing beaker each experiment and use clean DI water
to wash off the probes each time• Calibration of probes
– Make sure to calibrate each lab period • Reach Steady-State
– Allow experiment to run to completion – do not stop when it starts to level out but let it run it’s course
Conclusion
• This experiment allowed us to understand the importance of saponification and how to apply the same principles in industry
• Best conversion of NaOH with the confidence interval 99.97% +/- 0.07% was observed in part Bc. In this experiment we we used 2 (mL) NaOH (0.025M), 48 (mL) EtAc (0.3M), and 30 (mL) Water.
References1. Angelopoulos, A. P. Saponification Kinetics of
Ethyl Acetate. Rep. Cincinnati: University of Cincinnati, 2013. Print.
2. Levenspiel, O. (1972). Chemical Reactoin Engineering: Second Edition. New York: John Wiley & Sons, INC.
3. http://upload.wikimedia.org/wikipedia/commons/e/ea/Ethyl_acetate2.png
4. http://www.colby.edu/chemistry/PChem/lab/KineticsEster.pdf