ethanol (boiling point 78) and water can be separated using apparatus shown in figure 3. when the mixture of ethanol and water is heated both liquids vaporise. explain why the liquids then seperate. (3 marks)
The liquids separate because ethanol has a lower boiling point than water. When the mixture is heated, ethanol vaporizes first since it reaches its boiling point of 78 degree Celsius before water which has a boiling point of 100 degree Celsius. The gaseous ethanol rises up and enters the condenser where it is quickly cooled and condenses back into a liquid, which is collected separately from the water. The water continues to vaporize until it reaches its boiling point and is also collected separately. Therefore, the difference in boiling points of ethanol and water is exploited to separate them.
The separation of ethanol and water is possible due to the difference in their boiling points and the process of fractional distillation. Here's a step-by-step explanation:
1. Heating: As the mixture of ethanol and water is heated, both liquids reach their respective boiling points. Ethanol has a boiling point of 78 degrees Celsius, while water boils at 100 degrees Celsius.
2. Vaporization: At their boiling points, both ethanol and water convert into vapor (gaseous state). The energy absorbed by the liquids during heating provides the necessary heat for this phase transition.
3. Separation: The next step involves fractional distillation. The mixture enters the distillation apparatus (not shown in Figure 3), where it passes through a fractionating column. This column has a temperature gradient, with higher temperatures at the bottom and lower temperatures at the top.
a. Ethanol vapor: Since ethanol has a lower boiling point, its vapor primarily rises towards the top of the column, where the temperature is relatively lower.
b. Water vapor: Water, with its higher boiling point, remains mostly in the lower part of the column, where the temperature is higher.
4. Collection: As the ethanol vapor reaches the top of the column, it enters a condenser. In the condenser, the vapor cools down and condenses back into a liquid (ethanol). This liquid is collected separately.
5. Residue: The unvaporized water remains at the bottom of the column. While some water vapor may reach the top and condense, the majority of the water remains in liquid form. This water is collected separately.
In summary, the separation of ethanol and water is possible due to their different boiling points. By heating the mixture and utilizing fractional distillation, the two liquids can be vaporized, separated based on their boiling points, and condensed back into separate liquid forms.