Analysis Of Acetone And Toluene

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After starting with 30 mL of an unknown mixture of two solvents, fractional distillation and gas chromatography were used to identify the unknowns as acetone and toluene in a 1 to 2.04 ratio of acetone to toluene. Fractional distillation was first used to separate the unknown mixture into its components based on boiling point. Distillation refers to the method of separating components of a mixture through heating and cooling. Simple distillation, which is especially useful in the separation of less-volatile substances from volatile substances, such as sugar from water, can be used to separate a liquid-liquid mixture if the boiling points of the component liquids differ by more than 40-50°C. A plot of temperature versus volume for a simple …show more content…
By collecting the distillate at each temperature plateau, fractions containing a single component can be obtained. However, this technique does not work for solutions in which the boiling points of the components differ by less than about 40°C. In such cases, a plot of the temperature versus volume for a simple distillation would rise gradually and would not produce any plateaus. Additionally, the distillate would still contain a mixture of the volatile components, rather than one pure component. In order to separate the volatile components with similar boiling points, multiple simple distillations would have to be performed on the first fraction of distillate obtained, each one producing a more pure sample of the more volatile component. Because this method is inefficient and yields a very low volume of the target solvent, fractional distillation is instead used to separate a mixture of volatile solvents with similar boiling points. Fractional distillation is a method of separation similar to simple distillation, in that volatile components of a solution are separated based on boiling point. The addition of an insulated column to the distillation apparatus in fraction …show more content…
However, this temperature was lower than the boiling point of acetone, the most volatile solvent possibly present in the unknown solution, pointing to a source of error in the measurement of the temperature. This could have been due to an inaccurate thermometer or to an error in placing the thermometer too high. Because the boiling point was so low, the more volatile solvent was estimated to be acetone, which has a boiling point of 56.5°C. After fraction A was collected, the temperature of the stillpot was increased and should have produced a steady increase in a plot of the temperature versus total volume distilled while fraction B (a mixture of the two components) was collected, until a second plateau at the boiling point of the less volatile component. The temperature of the stillpot needed to be increased after collecting fraction A because the liquid left in the stillpot was then composed of a higher percentage of the less volatile component, with a correspondingly higher vapor pressure, meaning that it would boil at a higher temperature. However, during the course of the experiment, the temperature of the hot plate was turned up too much, so the temperature of the column was too high, the distillation occurred too quickly, and the reflux ratio was lowered. This resulted in the

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