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