Done By : A0098214AERIC KHONG MUN KIT A0097528N RON SIM A0105725LZHU KAI

Group : W7

Date of Experiment: 12/03/14

Demonstrators Signature : Grade:

1.0 SUMMARY

The objective of this experiment is to determine the phase diagram for three-component liquid system of Water-Butyl Acetate-Acetic Acid at room temperature and atmospheric pressure. The experiment was conducted in 2 different parts to construct both the tie-lines and solubility curve of the ternary phase diagram, which are plotted on the Gibbs triangle.

In the first part of the experiment, 4 samples with different composition of water, butyl acetate and acetic acid were well agitated with a mechanical shaker for at least an hour and allowed to attain equilibrium. Since acetic acid is soluble in water and butyl acetate, the amount of acetic acid distributed in the aqueous and butyl acetate phase can be determined by separating the aqueous and butyl acetate components before titrating with NaOH. The mass percentage of each component was calculated and used to plot the tie-lines.

For the second part of the experiment, 11 sets of water-butyl acetate samples with 0% to 100% concentration range of butyl acetate were prepared. These samples were then titrated with acetic acid until a homogenous phase was obtained. The volume of acetic acid added was recorded. It was used to determine the mass composition of each individual component in the mixture so that the points can be plotted for the construction of the solubility curve.

The Plait Point, defined as the critical mixing point where the tie-lines converge, can be obtained from the solubility curve and tie-lines. With the completed phase diagram, we are able to determine the physical state of any Water- Butyl Acetate-Acetic Acid liquid systems, be it homogeneous or not. From our data, the Plait Point was determined to be 17% butyl acetate, 42% water and 41% acetic acid by weight.

2.0 TABLE OF CONTENT

Section Page(s)

1.0 Summary 2 2.0 Table of Contents 23.0 Tabulation and Calculations 3-54.0 Discussion 6-85.0 Source of Error 8-96.0 Conclusion 97.0 Notation 108.0 Reference 109.0 Appendix 11-14

3.0 TABULATION AND CALCULATION

The following are the combination of results obtained from the experiment and the tabulated data for the construction of both solubility curve and tie lines on the ternary diagram of butyl acetate-water-acetic acid system.

(1) To determine the solubility curve of the system on triangular coordinate paper.

For this, we shall use the results from the series of 11 samples of selected composition of water and butyl acetate:-

Table 1: Titration results for 10ml of Butyl Acetate-Water sample with Acetic AcidExperimental ResultsCalculated values

Sample No.Volume of Water (mL)Volume of Butyl Acetate (mL)Volume of Acetic Acid required (mL)Mass of water (g)Mass of butyl acetate (g)Mass of acetic acid (g)Mass faction of waterMass fraction of butyl acetateMass fraction of acetic acid

10.509.502.200.508.362.310.0450.7480.207

21.009.002.601.007.922.720.0860.6800.234

32.008.004.202.007.044.410.1490.5230.328

43.007.004.903.006.165.140.2100.4310.359

54.006.005.654.005.285.930.2630.3470.390

65.005.006.005.004.406.290.3190.2810.400

76.004.006.606.003.526.920.3650.2140.421

87.003.006.607.002.646.920.4230.1590.418

98.002.007.008.001.767.340.4680.1030.429

109.001.005.809.000.886.080.5640.0550.381

119.500.504.059.500.554.250.6650.0380.297

Sample calculation for mass of a compound:-Taking water for sample 1 as an example:-

Sample calculation for the mass fraction of each compound:-Taking water for sample 1 as an example again:-

Then, the points were plotted to give the solubility curve of butyl acetate-water-acetic acid ternary system as the following:-Kindly refer to appendix A for a clearer and larger ternary diagram

(2) To establish the tie-lines and estimate the plait point

In order to establish the tie lines, we shall use the results from the titration of 4 specified samples with NaOH.

Table 2: Results for aqueous phase and BA phase titration with 0.501M sodium hydroxideAqueous Phase

SampleTotal volume of aqueous phase (mL)Total mass of aqueous phase (g)Volume of NaOH required to neutralize 2ml sample (mL)Concentration of NaOH providedNumber of mole of AA in 2mL sample (moles)Mass of acetic acid in aqueous phase (g)Mass fraction of acetic acid in aqueous phase (%)

163.064.268.100.501M4.05810-37.8212.17

259.060.1818.309.1710-316.5627.52

354.055.0826.5013.2810-321.9439.83

445.045.9028.4014.2310-319.5942.68

BA Phase

Total volume of BA phase (mL)Total mass of BA phase (g)Volume of NaOH required to neutralize 5ml sample (mL)Concentration of NaOH providedNumber of mole of AA in 5mL sample (moles)Mass of acetic acid in BA phase (g)Mass fraction of acetic acid in BA phase (%)

137.037.049.600.501M4.81010-32.1365.76

241.037.7224.1012.0710-35.93815.74

346.042.3247.3023.7010-313.0830.91

455.050.6055.1027.6110-318.2236.00

Sample calculation for the total mass of aqueous/BA phase:-Taking sample 1 in aqueous phase for example:-

Then, for the calculation of number of mole of AA in the aqueous phase,We first have to understand that one mole of NaOH is required to neutralize one mole of CH3COOH. Therefore, their molar amount must be equal at the end point.

For the mass fraction of AA in aqueous/BA phase, we convert the number of mole of AA from 2mL of the sample into the mass fraction. Example is shown below

Where NAA is the number of mole of AA in 2mL sample and MrAA = molecular weight of AA. Volume of sample used for titration for the BA phase is 5ml while the aqueous phase is 2ml.Taking aqueous phase of sample 1 for example:-

Using the mass fraction obtained from Table 1, we can construct the solubility curve, on the other hand, the mass fraction of Table 2 can be used to make 4 separate tie lines on the same ternary diagram. The resultant ternary diagram is as follows:-Kindly refer to appendix A for a clearer and larger ternary diagram

4.0 DISCUSSION

(1) Define and discuss on the Plait Point on your phase diagram and explain the method of construction.For a 3-component liquid system, the Plait Point is the point where the 2 coexisting phases of partially miscible components approaches each other in a same composition regarding to the density, at which a single phase of the system starts to occur. This point is also called the critical mixing point of the system.From the definition, the plait point should locate at where the tie-lines converge to. And it is not necessarily at the maximum point on the solubility curve. To prove the plait point attributes the above properties, the analysis is started from Gibbs Phase Rule Equation. For a 3-component liquid system, the equation is F = 5 P. For this experiment the temperature and pressure is specified and the equation reduces to F = 3 P. On the solubility curve, 2 phases coexists, leading to F = 1. At any point except plait point, by specifying the mass fraction of one component in either the aqueous or the BA phase, the overall composition and the other phase can be determined, by drawing a tie-line on the solubility curve. At the plait point, the tie-line becomes only a single point, and this shows the two phases have the same composition.To determine the plait point graphically, the 4 tie-lines obtained and discussed in the tabulation and calculation part are needed. Referring to the figure in Appendix A, two lines parallel to the opposite axis are drawn downwards, from the two ends of each tie-line. The intersection points of these two lines are noted and form a new curve. Then the plait line can be determined at which this curve intersects with the solubility curve (shown in the figure in Appendix A). And specifically, the point is at a composition of 41% for acetic acid, 17% for butyl acetate and 42% for water.(2) 100gm of mixture of 37% acetic acid and 63% butyl acetate are added to 60gm water and shaken rigorously at temperature until equilibrium is attained. Determine the weights and composition of the two phases using the phase diagram obtained.

From the information provided, we can construct a table to determine the mass fraction of each component in the ternary systemTable 3: Tabulation of mas of components to solve for Discussion Question 2ComponentMass of component (g)Total mass of the ternary system (g)Mass fraction of each component

Acetic acid37g1600.231

Butyl acetate63g0.394

Water60g0.375

We can then translate the mass fraction into points on the ternary diagram:-

Kindly refer to appendix A for a clearer and larger ternary diagram

From reading of the ternary diagram, the compositions of the two phases are the following

BA phase (read from point A): 18% acetic acid 78% butyl acetate 4%waterAqueous phase (read from point B): 29% acetic acid 3.5% butyl acetate 67.5% water

Using lever rule, it can be found that the ratio between line segments AC to CB is 21:19, Therefore, we can also establish that

Then, we can find that the mass of BA phase = (21/19) (160-mass of BA phase) since mass of both phase adds up to 160gBy solving the equation above, mass of BA phase = 76g while mass of aqueous phase = 84g

From these readings, we can also gauge the accuracy of the ternary diagram prepared.Mass of butyl acetate in BA phase = 59.28gMass of butyl acetate in aqueous phase = 2.94Supposed total mass of BA in the whole system = 63gThe deviation of expected value = 63 (59.28 + 2.94) = 0.78gPercentage error = 0.78/63 100 = 1.24%

(3) Briefly discuss on the effect of the temperature and pressure on the phase diagram.Temperature

Water and butyl acetate has very low solubility in each other and the addition of sufficient acetic acid is required for the 2 phases to coalesce and form a homogenous phase. When temperature increases, the kinetic energy of molecules increases. This allows for both liquids to overcome their separation barrier and become more soluble. Therefore, with increase in temperature, lesser amount of acetic acid will be required for the 2 phases to become homogenous. This will mean that the solubility curve on the phase diagram will shift away from the axis of acetic acid with increasing temperature.

In addition, with increase in temperature and solubility of water and butyl acetate, there is lesser area in the phase diagram where the 2 phases can coexist. Hence, the area enclosed by the solubility curve decreases with increasing temperature. As temperature continues to increase, it will reach a point where phase separations would no longer occur. This is known as the Upper Critical Solution Temperature. There will be complete miscibility of all 3 components from this particular temperature onwards.

Pressure

Since liquids are considered incompressible, the thermodynamic property changes due to pressure are negligible as this experiment involves a 3 component liquid system. For a very high or low pressure system however, such changes can become significant, but for this experiment which is conducted at atmospheric pressure, we can safely assume that variations in pressure will cause negligible effects on the solubility curve on the phase diagram.

5.0 SOURCES OF ERROR(1) When the calculation being done, the density of each phased used was assumed to a fixed number. And this differs to the real situation. Even if it is in the same phase, when the compositions change, the density would also change. This point would cause an error on plotting the tie-line, solubility curve and the successive Plait Point.(2) In the 3rd step of the experimental procedure, it is difficult for one to determine the end point of the titration. By naked eyes, it is imperceptible whether the single homogeneous phase is formed among each single drop. Therefore, the results would involve certain degree of estimation. This also results in an inaccuracy of the diagram.(3) For the titration part, another error can come from the methyl red indicator. As the indicator is also in an aqueous phase, some water would be added in by using the indicator. The water added in would influence the composition of the original liquid to be tested.(4) The reagents used in the experiment such as BA and acetic acid are highly volatile and could have evaporated. The amount measured of the reagents could be different from the beginning. To minimize this error, the conical flasks were kept stoppered when not in use. However, a small amount of evaporation could not be avoidable.(5) Parallax error might have been introduced when reading off from the burette due to the restriction from the experimental set-up in the fumehood. This could introduce some errors in the titration results obtained, and affect the position of tie-lines and plait point.

(6) The separating funnels were used to separate the aqueous phase from the butyl acetate phase which could introduce significant error in the volume of each phase obtained. More accurate electronic separating device should be used to minimize this source of error so that the 2 phases can be better separated and reflect a more accurate result for acetate composition calculation during the titration process.(7) The three mixtures were only assumed to have reached equilibrium after agitation for an hour when this might not be the case. More time should be given for the mixing of the mixtures such that equilibrium can be more accurately assumed. An equilibrium point has to be achieved in order to obtain accurate results for the tie-line.6.0 CONCLUSIONThe objectives of the experiment were mainly achieved by plotting the solubility curve of the 3-component liquid system of water, butyl acetate and acetic acid (at 1.008 bar and 296.15 K) on the triangular phase diagram. Tie-lines corresponding to the 4 mixtures of varying composition and the plait point were also determined by using the experimental data. The plait point was defined to be at a mass composition of 41% acetic acid, 17% butyl acetate and 42% water. The literature value of this plait point found in an experiment conducted by Hirata & Hirose at 303.15K is 38.23% acetic acid, 33.24% butyl acetate and 25.53% water. This literature value seems much different from the one obtained from the experiment. While one factor causing the difference could be the different temperatures, it is likely to be accrued to a great extent to the inherent experimental errors discussed in Source of Error section.7.0 NOTATIONAA Acetic AcidBA butyl- acetate8.0 REFERENCESHirata, M., Hirose, Y., Physical Properties of Ternary System Acetic acid-Water-Butyl acetate, Chemical engineering 407-414, 1963. Retrieved from https://www.jstage.jst.go.jp/article/kakoronbunshu1953/27/6/27_6_407/_pdfInce E & Kirbaslar, 2002. Brazilian Journal of Chemical Engineering, Vol 19, No 2, pp 243-254, Retrieved from http://www.scielo.br/pdf/bjce/v19n2/10666.pdf

University of Vermont, Equilibrium V. Vermont, 2005. Retrieved from http://www.uvm.edu/~dsavin/courses/chem162/lectures/eqm5.pdf

9.0 APPENDICESAppendix A Ternary diagramsAppendix B Lab T3 Experiment DatasheetAppendix C Experiment T3 Risk Assessment Form

APPENDIX A- Ternary DiagramsFigure 1: Ternary diagram with tie lines plotted based on experimental results Figure 2: Ternary diagram with points used for Discussion Question 2

Figure 3: Ternary diagram with constructed lines for determination of plait point.10