Physical Principles II

CEBU CITY Chemical Engineering Department

Name: Juphil Lamanilao Date: October 15, 2009

Course & Yr: BSChE-4

I.TITLE: Hydrolysis of Methyl Acetate

II.OBJECTIVE:

To determine the specific rate constant at two or more given temperatures.

III.APPARATUS:

Thermostat at 25ºC & 35 ºC, (3) 250-ml Erlenmeyer flasks, (2) 125-ml Erlenmeyer flasks, 5-ml pipette, 100-ml pipette, stop watch, Ethyl acetate, 2 liters 0.1N NaOH, 500 ml 0.1N HCl, distilled water, ice.

IV.SKETCH:

Hydrolysis of Methyl Acetate 1

Physical Principles II

V.TABULATED DATA & RESULTS:

@ 25ºC VHCl(ml) VH2O(ml) Valiqout(ml) VNaOH(ml) t(min)1 50 50 5 3.4 1.592 50 50 5 3.5 2.443 50 50 5 3.7 3.07

@ 35 ºC VHCl(ml) VH2O(ml) Valiquot(ml) VNaOH(ml) t(min)1 50 50 5 4.2 2.422 50 50 5 5.0 1.89

@ 25ºC 1 st run 2 nd run 3 rd run @35ºC 1 st run 2 nd run NNaOH(mol) 0.1811 0.1864 0.1970 NNaOH(mol) 0.223 0.2663NHCl(mol) 0.0050 0.0050 0.0050 NHCl(mol) 0.0050 0.0050NHOAc(mol) 0.1761 0.1814 0.1920 NHOAc(mol) 0.2187 0.2613Co(mol) 0.5113 0.5113 0.5113 Co(mol) 0.5113 0.5113C(mol) 0.3352 0.3299 0.3193 C(mol) 0.2926 0.2500t(min) 10 10 10 t(min) 10 10k(s-1) 0.0007

040.00073

00.00078

5k(s-1) 0.0009

300.00120

The average constant K, calculated from the equation lnCo-lnC = kt, was found to be 0.000740s-1 at 25ºC and 0.00108s-1 at 35ºC, both at constant 10 minute interval. As the temperature increases, the specific rate also increases and the final concentration is inversely proportional to the specific rate constant.

VI.SAMPLE COMPUTATIONS:

NNaOH = NHCl + NHOAc NHOAc = 0.1761 mol

NNaOH = 2.13 g/ml * 3.4 ml * mol/40g = 0.1811 mol

NHCl = 0.1 eq/1000mol * mol/eq * 50 ml = 0.005 mol

NHOAc = NEtOAc consumed

C = Co - NHOAc

C = 50 ml * 0.901 g/ml * mol/88.105g = 0.3352 mol

C = 0.5113 mol – 0.1760 mol = 0.3352 mol

lnCo – lnC = kt

ln0.5113 – ln0.3352/600 s = k = 0.0007040s -1

Hydrolysis of Methyl Acetate 2

Temp(ºC ) t(min)EtOAc 25 7.32EtOAc 35 5.93

Physical Principles II

VII.DATA ANALYSIS:

The experimental value obtained for the specific rate constant at 25оC approaches 0.000740s-1 for (3) runs @ 10 minute interval on the other hand the obtained specific rate constant value at 35оC approaches 0.00108s-1 for the same time interval. As temperature increases the specific rate constant also increases, which pertains that temperature is directly proportional to specific rate constant. From the results obtained, the final concentration (C) is a function of time (t). Plotting lnC against time, the reaction will cease and reactants utterly dissociate.

VIII.APPLICATION TO ChE:

In the production of polyvinyl alcohol, methyl acetate is typically produced as a by-product. In order to produce polyvinyl alcohol at a reasonable cost, it is necessary to recover acetic acid and methanol from the methyl acetate so produced. This is typically done by the hydrolysis of methyl acetate with water to produce a mixture of methyl acetate, methanol, acetic acid and water, which mixture is subsequently separated to isolate the acetic acid and methanol. Effort has long been directed toward the improvement of the efficiency of this reaction and the subsequent separation. Since the hydrolysis process is an equilibrium reaction, it can be driven to greater acetic acid production by the addition of water. However, it is also desirable to keep the concentration of water to a minimum, since any water added to the system must later be removed from the reaction products. This removal is generally carried out by a distillation process in which any added volume increases the energy consumption. Other application involved the inversion of cane sugar and irradiation of strong infrared from free electron laser source

IX.CONCLUSION:

The hydrolysis of methyl acetate is a reversible reaction as shown;

MeAc + H2O ↔ HAc + MeOH.

In dilute aqueous solution, water is present in such excess that its concentration remains unchanged during the reaction, and if the experiment is carried in a solution of a strong acid catalyst, the formation of acetic acid will not effectively change the concentration of hydronium ions. Also, the ice used to quench the reaction mixture should be made with distilled water

Hydrolysis of Methyl Acetate 3

Physical Principles II

otherwise it increases the ionic strength of the solutions as it melts due to which dissolved salts go into the solution.

Hydrolysis of Methyl Acetate 4