a) what is meant by the term flooding of the fractionating column and what causes it?
b) Assume that no azeotropes are formed, would it be easier to separate n-hexane and benzene or n-hexane and toluene by distillation? expalin?
Thank you!
Scroll down to flooding and read about that.
Look up the boiling points of n-hexane, benzene and toluene. It should be easier to separate the two with the greater boiling point difference.
a) Flooding in a fractionating column refers to a condition when there is excessive liquid in the column, which hampers the separation process. It occurs when the liquid flow rate exceeds the rate at which the vapor can rise through the column. This leads to a buildup of liquid in the column, preventing proper separation of the components.
Flooding can be caused by several factors, including:
1. High liquid flow rate: When the liquid flow rate is too high, it can overwhelm the column's capacity to handle the liquid, causing flooding.
2. Insufficient vapor flow: If the vapor flow rate is not sufficient to carry the liquid up the column, it can lead to flooding.
3. Inadequate column design: Poor design, such as incorrect tray spacing or inadequate vapor-liquid contact, can contribute to flooding.
4. Presence of contaminants: Impurities or contaminants in the liquid or vapor streams can create obstructions and contribute to flooding.
b) When considering the separation of n-hexane and benzene versus n-hexane and toluene by distillation, it is important to understand their boiling points.
The boiling point of n-hexane is around 69°C, while benzene boils at around 80°C, and toluene boils at around 110°C.
Since the boiling points of n-hexane and benzene are relatively close, it would be more difficult to separate them by distillation since the temperature difference between their boiling points is small. This small temperature difference leads to a lower vapor pressure difference between the two components, making the separation less efficient.
On the other hand, the boiling point of n-hexane and toluene has a larger difference, making it easier to separate them by distillation. The larger temperature difference results in a higher vapor pressure difference, allowing for better separation in the fractionating column.
In summary, when no azeotropes (constant boiling point mixtures) are formed, it would be easier to separate n-hexane and toluene compared to n-hexane and benzene by distillation due to the larger difference in their boiling points.