Ethanol has a boiling point near 78°C and water has a boiling point of 100°C. A lab technician accidentally diluted a sample of ethanol with water.
Explain
how ethanol can be separated. Justify your choice of separating technique.
(5 marks)
Ethanol and water can be separated by using the technique of fractional distillation. This method exploits the difference in the boiling points of the two liquids. As ethanol has a lower boiling point than water, it vaporizes first when the solution is heated. The vapors of ethanol are then condensed and collected separately from the water.
To perform fractional distillation, the technician should heat the solution in a flask and allow the vapors to pass through a fractionating column, which has several condensing surfaces. As the vapors rise through the column, they condense and evaporate multiple times, causing the separation of the ethanol and water vapors. The ethanol vapors, now more concentrated, are then collected through a condenser, while the water is left behind.
Fractional distillation is the most suitable technique for separating ethanol and water as it is a simple and efficient method. It allows the separation of two liquids with close boiling points without the need for complex chemical reactions or high-energy inputs. Additionally, it is a common technique used in many industrial processes that require the separation of different liquids based on their boiling points.
However, note that ethanol and water form an azeotrope at 95.63% ethanol/ 4.37% water which means that 100% separation can NOT be realized using this technique alone.
Thank you for pointing that out. It is true that an azeotrope is formed between ethanol and water at a certain ratio (in this case, at 95.63% ethanol/4.37% water). This can make it difficult to achieve complete separation of the two liquids using only fractional distillation. At this particular ratio, the boiling point of the mixture is lower than that of pure ethanol or water, making it impossible to separate them using fractional distillation.
To achieve higher purity of ethanol, additional steps such as azeotropic distillation or further purification using molecular sieves may be required. Alternatively, other separation techniques such as membrane separation, adsorption, or distillation using alternative solvents may be explored.
To separate ethanol from water, you can make use of the difference in boiling points. Since ethanol has a lower boiling point than water, the technique of distillation can be employed for separation.
Distillation involves heating the mixture to its boiling point and collecting the vapor that is produced. The basic steps to perform distillation are as follows:
1. Set up a distillation apparatus: This typically includes a round-bottom flask containing the mixture to be separated, a condenser to cool and condense the vapor, and a collection flask to collect the separated components.
2. Heat the mixture: Apply heat to the round-bottom flask to increase the temperature of the mixture. As the temperature rises, the component with the lower boiling point (ethanol) will vaporize first.
3. Collect the vapor: As the vapor rises, it enters the condenser, which cools and condenses it back into a liquid state. The condensed liquid is collected in a separate container (collection flask).
4. Separate the components: After the distillation process is complete, the collected liquid will consist mostly of the lower boiling component (ethanol), while the higher boiling component (water) will remain in the original flask.
Justification for using distillation as the separating technique:
Distillation is an ideal method for separating ethanol from water due to the significant difference in their boiling points. The boiling point of ethanol is 78°C, while the boiling point of water is 100°C. This difference allows for selective vaporization and condensation of ethanol while leaving most of the water behind. Distillation is a commonly used technique in laboratories and industries for separating liquids based on their boiling points.