ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT
Separation of an Unknown Binary Mixture by Simple and Fractional Distillation Pilapil, Emerson M. , Pimentel, Maria Danica B. *, Rendor, Jake Vincent O. Group 13 Department of Chemistry, College of Science University of Santo Tomas, España, Manila 1008
Distillation is a method or process of separating mixtures based on differences in their volatilities in a boiling liquid mixture. Distillation is done with the use of specific set-up shown in Figure 1 and 2. Through this process, the identities of the unknown components in the solution can be determined through the obtained boiling points. In the experiment, the percent low boiling point and percent high boiling point were computed. There is a list of probable unknown volatile components in the mixtures. This list was obtained through comparisons of the boiling points. Abstract.
INTRODUCTION
Distillation is an old process of separating two or more volatile mixtures. It was already being done as early as the 2nd millennium BC. Distillation uses the different boiling points of volatile mixtures or substances in order to separate them. Volatile mixtures or substances are solids and liquids that readily changes to its gaseous state. The rate of change in physical properties or phase of this mixtures or substances can be increase through heating. The application of distillation can be seen in the fields of food processing, industrial distillation, laboratory scale, and herbal distillate. The food and herbal distillate differs from the industrial and laboratory scale because distillation is not used as purification method but more as a transferri transferring ng method of volatile volatile components. components. There is a specific specific difference difference between industrial industrial and laboratory scale because in laboratory scale it is performed by batch-wise while in industrial distillation it is commonly continuous. There are a lot of different types or kinds of distillation but in this experiment only two are being being introd introduce uce and used, used, simple simple and fract fraction ional. al. Simpl Simplee and fracti fractional onal distil distillat lation ion are exampl examples es of labora laborator tory y scale scale disti distilla llati tion. on. Simpl Simplee distil distillat lation ion is the most most basic basic set-up set-up for
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT distillation. In simple distillation, the volatile mixtures are heated, thus vapors are produced. These vapors are immediately channeled in the condenser where it is cooled and condense. The distillate produced in the simple distillation is not pure because its composition will be similar to the composition of vapors at a specific temperature and pressure. Because of this, simple distillation is not usually used. It is used when separating volatile components whose boiling points are more than 25°C or volatile components from involatile mixtures such as oil. Fractional distillation is commonly used in volatile mixtures that have boiling points lower than 25°C. Since the components usually have low boiling points, it is necessary to repeatedly vaporize and condense the components. In fractional distillation, the sample or mixture is heated to form vapors. As the vapors are produce, it rises to the fractioning column where it cools and condenses on the condenser walls and the surfaces of the packing material (tin foil). Here, the condensate continues to be heated by the rising hot vapors and it vaporizes once more. Through this process the components are repeatedly vaporized and condensed. In the experiment, the components of an unknown solution can be separated and determine how many components are present. After the experiment, a distillation curve can be easily constructed and the percentage of the components can be calculated. There is a distinction between the efficiency of both distillation processes in separating mixtures. EXPERIMENTAL
Eight pieces of 13 x 100 mm test tubes were calibrated to 3mL. All the glassware needed to perform simple/ fractional distillation was laid out with aluminum foil coiled as a packing material. The apparatus were assembled according to the figures 1 and 2. An amount of 25mL of the unknown assigned was placed on the 50mL distilling flask and 2 pieces of boiling chips was added. The water was turned on gently in the condenser. The distilling flask was heated until the
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT first drop of distillate reached the receiver. The temperature of the first drop was recorded. The heat was adjusted to have a rate of 1-2 drops per second. The temperature after every 3mL of distillate was recorded. After the 8 calibrated test tubes were filled, the data was recorded with temperature versus volume (mL). The temperature of the first drop corresponds to the zero volume. Stop the distillation when all of the 8 test tube is filled or when there is not much left in the round bottom flask. The boiling temperature was graph with temperature versus volume of the distillate. The percent of low and high boiling component was calculated. The weight of the left over unknown, if any, was measured to compute for the percentage loss.
Figure 1: the set-up for simple distillation
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT
Figure 2: The set-up for fractional distillation
RESULTS AND DISCUSSION
Tables 1 show the different temperature recorded during the distillation process, both in simple and fractional, in their corresponding volume. Table 1: The recorded temperature versus the corresponding volume in both simple and fractional distillation
TEMPERATURE OF DISTILLATE (°C) SIMPLE FRACTIONAL DISTILLATION
DISTILLATION
65
57
3
81
67
6
84
68
9
89
61
12
92
130
VOLUME(mL)
1st drop (0)
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT 15
98
134
18
98.5
132
21
110
NO MORE UNKNOWN SOULTION
24
130
NO MORE UNKNOWN SOLUTION
In Figure 3, the temperature of the distillate in the simple distillation was graph in correspond to its volume.
Figure 3: The graph representing the data gathered in the simple distillation set-up
In Figure 4, the temperature of the distillate in the fractional distillation was graph in correspond to its volume.
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT
Figure 4: The graph representing the data gathered in the fractional distillation set-up
In Figure 5, both data gathered from simple and fractional distillation was graph together for comparison reasons.
LEGEND:
-simple -fractional
Figure 5: The graph representing both the data of simple and fractional distillation
Table 2 contain the percent (%) low boiling and percent (%) high boiling of both simple and fractional distillation.
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT
% Low boiling % High boiling
Simple Distillation 60% 36%
Fractional Distillation 12% 48%
Table 2: Tabular representation of the % low boiling point and %high boiling point of simple and fractional distillation
COMPUTATIONS:
For simple:
For Fractional:
Table 3 show the possible unknown contain in the unknown solution and their corresponding boiling point.
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT POSSIBLE UNKNOWN
BOILING POINT(°C)
ACETONE
56.53°C
ISOAMYL ACETATE (banana oil) CYCLOHEXYLAMINE
142°C 134°C
FLUOBORIC ACID
130°C
METHANOL
64.7°C
ETHANOL
78.4°C
Table 3: Tabular representation of possible identities of the unknown solution and their corresponding boiling point
The key points in this experiment are boiling point and vapor pressure of liquids. Both boiling point and vapor pressure are colligative properties. They are inversely proportional since the higher the vapor pressure of a liquid at a given temperature, the lower the boiling point of the liquid. The boiling point is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid while vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. The basis for the separation of liquid mixture by distillation is the characteristics of the mixture. The properties of the mixtures that are distilled have a big difference in their boiling points and usually these mixtures are volatile mixtures, easily turn into its gaseous state. Since boiling point is one of the basis, the one with the lowest or lower boiling point will be the first one to be distilled than those with higher boiling point. The condenser is a laboratory apparatus that help cool down the vapor. Water passes through the whole length of the condenser to allow heat to transfer to the water. The water inlet
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT is on the bottom because when it is in the bottom it allows continuous and slow cooling and condensing of the vapor. The distilling flask or round bottom flask should be avoided to be empty because it could explode or break the glass wares. It could explode since there is pressure inside and it is heated. It could cause excited or increase in the energy of the atoms of the gaseous forms of the volatile components. Boiling chips provide surfaces on which bubbles can form as the liquid boils. If not used, the liquid can get hot without boiling and it will "bump", sending liquid (instead of vapors) into the distillation column or condenser. If it is added after the heating has started it would be too late since it will already bump or liquid will be distillate instead of the vapors. The fractionating column is an essential apparatus used in the distillation of liquid mixtures to separate it into its component parts, or fractions, based on the differences in their volatilities. It aids in separating the mixture by allowing the mixed vapors to cool, condense, and vaporize again. A packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This can either be random dumped packing or coiled thin foil. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. The packing material is also used so that the vapor does not go to the condenser immediately because it needs to be repeatedly vaporize and condense.
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ORGANIC CHEMISTRY 201 LABORATORY FORMAL REPORT CONCLUSION
In conclusion, fractional distillation is more reliable than simple distillation. In fractional distillation, the components can be separated purely while in simple it is not. But in some cases, simple distillation is enough to be able to separate the components purely.
REFERENCES
B.G., Segal.Chemistry; Experiment and Theory. New York, USA; Wiley. (1989). pp. 215-216. D. D., Ebbing. General chemistry. Boston : Houghton Mifflin. (1996). pp. 42-44. J.W. , Hagen. Empirical Chemistry; a Quantitative Laboratory Program. San Francisco: W.H. Freeman. (1972). pp. 283-286.
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