Simple and Fractional Distillation

I. Introduction

Distillation is one of the oldest and still most common methods for both the purification and the identification of organic liquids. It is a physical process used to separate chemicals from a mixture by the difference in how easily they vaporize. As the mixture is heated, the temperature rises until it reaches the temperature of the lowest boiling substance in the mixture, while the other components of the mixture remain in their original phase in the mixture. The resultant hot vapor passes into a condenser and is converted to the liquid, which is then collected in a receiver flask. The other components of the mixture remain in their original phase until the most volatile substance has all boiled off. Only then does the temperature of the gas phase rises again until it reaches the boiling point of a second component in the mixture, and so on.

There are two types of distillation namely simple distillation and fractional distillation. In this experiment the efficiency of the two types of distillation will be compared.

II. Methodology

The following is the methods needed to perform fractional distillation. The gather the materials needed for the experiment such as the fractional distillation set-up, alcohol lamp, and vodka after which start performing the experiment.

1. Assemble the distillation set-up. 2. Prepare atleast 30 test tubes calibrated down to the 0.5 ml and number each test tube accordingly. 3. Introduce 30 ml of vodka into the quick-fit distilling flask it will serve as the sample for the experiment. 4. Start heating the flask by rotating the alcohol lamp below it. Heat until the vodka starts to boil. 5. Record the temperature at the first drop of the distillate. 6. Collect only 0.5ml each of the distillate into the calibrated and numbered test tubes. NOTE: Be aware with the temperature at which the distillate is collected. 7. Continue collecting 0.5 ml of distillate in every test tube you will only stop when the temperature reaches about 100˚C. 8. Place 3-5 drops of the distillate on a watch glass and apply a lightened match.

III. Presentation of Data

The table below shows the data gathered by the group in the experiment.

Test Tube | Temperature(C˚) | Test Tube | Temperature(C˚) | 1 | 78 | 14 | 80 | 2 | 78 | 15 | 81 | 3 | 79 | 16 | 82 | 4 | 78 | 17 | 88 | 5 | 79 | 18 | 98 | 6 | 79 | 19 | 100 | 7 | 79 | 20 | 100 | 8 | 79 | 21 | 100 | 9 | 79 | 22 | 100 | 10 | 80 | 23 | 100 | 11 | 80 | 24 | 100 | 12 | 80 | 25 | 100 | 13 | 80 | 26-30 | N/A |

For us to clearly visualize the data here is a line graph showing the temperature of the first drop of alcohol for each test tube.

IV. Results and Discussions

Computations:

% alcohol=volume of ethanolvolume of samplex 100

% loss=volume of sample-( volume of distillate+volume of residue)volume of samplex 100

% error=|Theoretical %-Actual %|Theoretical %x 100

SOLUTION:

Percentage of Alcohol | Percentage of loss | % alcohol=v ethanolv samplex 100% alcohol=7 ml30 mlx 100% alcohol=23.33% | % loss=v sample- ( v distillate+v residue)v samplex 100% loss=30 ml (12. 5 ml+7.8 ml)30 mlx 100% loss=32. 33%*Formula in getting the volume of distillate and volume of the residuev distillate =v of the test tubes v distillate =25 x0.5 mlv distillate =12.5 mlNote: 25 = test tubes used; 0.5 volume of distillate in the test tube.v residue=v of sample left in flask | Percentage of Error | | % error=|Theoretical %-Actual %|Theoretical %x 100% error=|40% -23.33 %|40 %x 100% error=41.68%* Formula in getting the theoretical percentage. Note: The value for the proof is found on Alcohol labels.
Theoretical % =Proof2 | |

Simple Distillation vs. Fractional Distillation:

Fractional Distillation Set-Up Simple Distillation Set- Up
The choice of whether to use fractional distillation or simple distillation depends on the two liquids being separated. Typically, using simple distillation is preferable because the apparatus is, well, simpler, and a simple distillation typically goes faster than a fractional distillation (and requires less energy). On the other hand, fractional distillation gives better separation between the liquids. The choice of whether to use simple or fractional distillation, then, depends usually on the difference in boiling temperatures between the two liquids. If there is a large difference in the boiling points (>70oC) between the two liquids then simple distillation is probably the best option. On the other hand, if there is only a small temperature difference between the two liquids a fractional distillation is the preferable option. | Simple distillation | Fractional distillation | Advantages | * simpler setup than fractional * faster distillation times * consumes less energy than fractional distillation | * much better separation between liquids than simple distillation * can more readily purify complex mixtures than simple distillation | Disadvantages | * requires the liquids to have large boiling point differences (>70oC) * gives poorer separation than fractional distillation * only works well with relatively pure liquids | * more complicated setup than simple distillation * takes longer for liquids to distill * consumes more energy than simple distillation | Best used for: | Separating relatively pure liquids with large boiling differences or liquids with solid impurities. | Separating complex mixtures of liquids with smaller boiling point separations. |