Experiment # 2

Maria Mota Experiment #2 Sarah Zigmont Simple and Fractional Distillation and Gas Chromatography Procedure: In an Erlenmeyer flask 60 ml of acetone/1-propanol mixture were added. Then the apparatus for distillation was assembled, when the heating mantle was also ser up it was turned to 60 volts. Then the mixture started to boil and sample being to be collected, at this point the temperature and the volume were recorded, for both simple and fractional fraction A, B and C were collected respectively. For the fractional distillation a fractional distillation column was used. After each distillation was complete the gas chromatography was done. Discussion: Acetone has a boiling point of 56.2 C and 1-propanol has a boiling point of 97.4C. the simple distillation of sample A had 97.8% acetone and 2.2 % 1-propanol the sample distillation of simple C had a 14.4% of acetone and 85.6% of 1-propanol. For fractional distillation fraction A had a 98.4% acetone and 1.6% 1-propanol and fraction C had a 0.01 acetone and 99.9 1-propanol. Since acetone has a BP of 56.2 C the peaks of the graph are expected. Sample A has a higher percent of acetone. Sample C has a lower percent of acetone because it has evaporated and a higher percentage of 1-propanol since its BP is 97 C. The fractional distillation follows the same pattern. As shown in the results the more efficient method of separation of 1-propanol from a mixture of acetone and 1-propanol is fractional distillation. Fractional distillation works better when there is a large difference between boiling points amongst the compounds in the mixture. The substance with the lowest BP will condense at the highest point in the column, while the lowest boiling point will condense in the lower column. A substance can be separated and processed and the graphs of the fractional distillation are better defined than the ones in the simple distillation there for the best method for this separation was fractional distillation. Simple Distillation: SFA: These calculations are based on the graphs printed from beach board. A1= w*1/2h*h= 5mm*1/2(31mm)*31mm= 2402.5 mm A2= 3mm*1/2(6mm)*6mm= 54mm AT= 54mm+2402.5mm= 2456.5mm %A1=A1/AT*100%= 2402.5mm/2456.5mm*100 %= 97.8% %A2=A2/AT*100%=54mm/2456.5mm*100%=2.2% The same calculations were done for SFC, FFA and FFC

SFC A1=181.5 mm A2= 1083mm AT=1264.5mm %A1= 14.4% %A2=85.6 % FFA A1=3062.5 mm A2= 50mm AT=3112.5 %A1= 98.4% %A2=1.6 % FFC A1= 2.25mm A2= 2744mm AT=2746.25mm %A1= 0.1 % %A2= 99.9 % Since my sample was not ran in the GC, my calculations are based on volume, but this data is not used for the discussion. It was just to fill in the blank. SFA V1= 2ml V2=45ml VT=47ml %V1= 2ml/47ml*100%= 4.3% %V2=45ml/47ml*100%=95.7% Simple Distillation Fraction Volume A 2ml C 45ml Fractional Distillation Fraction Volume A 20.0ml C 52.0ml

% Acetone 4.3 95.7 %Acetone 27.8 72.3

%1-propanol 95.7 4.3 %1-propanol 72.2 27.7

Temperature 62 C 97.1 Temperature 62.2 97.9

Distillation in a mixture of compound is used to identify a compound and this identification can be done by comparing different physicals properties such as temperature; boiling point of a compound can be determinate by distillation this is the reason why distillation is used to identify compounds, on the other hand distillation can be also used for purification of a organic compound.

During distillation the hot vapor produced is measured by a thermometer then is passed thought a condenser that cools down the vapor and at the same time condenses it, there for the organic compound with a lower boiling point will evaporate first in this case acetone who has a boiling point of 56°C. There are a couple of differences between simple and fractional distillation as shown in the graphs below.

Fractional destillation data ml FFA

FFA

FFC

Simple destillation data Temp

0.01 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 39 41 43 45 47 49 51 52

ml 57.4 58 58.7 59.2 59.5 60.2 60.6 60.9 61.5 61.9 62.2 62.9 62.9 63.4 65.9 66.3 67.8 69.8 74.5 85.7 91.5 92 93.2 94.1 95.3 96.8 96.9 97.9

SFA SFB

SFC

Temp 0.01 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 37 39 41 43 45

60.4 62 66.4 67.3 68.4 69.2 69.6 69.9 70.3 72.1 72.9 74.3 75.7 76.9 79.5 80.2 84.1 85.8 87.3 90.5 91.9 93.3 96.9 97.1

Simple Distillation 100

95

T e m p e ra tu re (C )

90

85

80

75

70

65

60

0

5

10

15

20

25

Volume (ml) Series 1

30

35

40

45

In terms of using simple versus fractional distillation there are significant differences in the case of simple distillation process the sample obtained can be less pure in contrast with fractional distillation. In the case of fractional distillation the column improves the separation process by increasing the surface area available to establish vapor liquid equilibrium, this difference is observed in the graphs above, when we look at the slope of fractional it slope is greater than the slope of simple, giving with this a better surface area and a consequence a more pure sample using fractional distillation. As mentioned before the rings create a bigger surface area with this increasing the possibilities of condensation and with this equilibrium between vapor and liquid producing a more clear sample and better reading in temperature of each sample with this making easier to identify compounds by their boiling point and in the case of purification because the impurities get tramp on the fractional column and then flow back to the mixture instead of passing thru the distillation column, with this giving us a more pure sample. GC provide us with the information necessary to know how many compounds were on the mixture, and by giving us the curves we can measure the area under the curve and then find out the percent of each compound present on the mixture, this also helps us to realize how clean the mixture was. By calculating retention times we are calculating the time it takes for a compound to elute from the column and this will help to identify the compound; we can find out the time at which a compound in the mixture was being obtained and how temperature and time are related, for example a two compounds of similar boiling points the temperature will increase as time increases gradually on the other hand two compounds with a great difference in boiling point, the temperature will increase faster in a shorter period of time. Standards are run to compare the results because standards are run when only the specific compound was distillated therefore is more pure than the same sample being distillates with another compound. To calculate the area under each curve the width and length of the peak were measured then those were added and then each one divided by the total area of both times 100%. The humps indicate the percentage of each substance in the mixture obtained for the distillation. The mixture of acetone/1-propanol show 4 peaks because in this case the standards of both compounds are being used for comparison. The shoulder on a peak indicates the presence of impurities, from another compound on the mixture or from another agent such as the solution that the injection is cleaned with. The parameter that can be altered when performing the injection to avoid being off scale can be the simultaneously at which the injection is released and the start bottom pushed, because this two need to be done at the same time. The mistake that the student did when setting up the apparatus was when he set up the distillation head, at this point if the entire bulb of the thermometer needs to be positioned below the side arm of the distillation head; the entire bulb must be deep in the vapor to achieve an accurate temperature reading. The molar composition of the vapor in equilibrium with a boiling liquid that has a composition of 50% A and 50 % B is correlated with their boiling points this means that both of the substances have a similar boiling point therefore the amount collected from

each one should be similar, and there for their area under the curve should be similar when running a GC. The composition of a boiling liquid that produces a vapor of 60% A and 40% B, in this case the boiling point is a little bit higher in one of the compounds there for the area under the curve for both peaks when running a GC will have a remarkable difference and also a good separation is better observed. .