Question

based on a fractional and dstillation lab answer the following:

1. why is it important that the coolong water in a distillation apparatus enter the condenser jacket at the lower end and exit at the upper?

2. what effect would a reduction in atmosphericpressure have on the boiling point of ethyl acetate? explain

3. what is themperature gradient in the Vigreux column; is it low near the bootm and high near the top or vice versa?

Answer 1

Fractional distillation is a distillation technique used for the separation of the mixture of miscible liquids. These liquids dissolve in each other. Fractional distillation separate the components of a mixture by repeated distillations and condensations.

1. This is to ensure the most effective cooling. During distillation, vapors are formed in the heated distillation flask. The condenser cools these vapors condensing them back to liquid droplets that flow down the condenser into the receiver flask. When water enters the bottom, and is slightly warmed by the condensing liquids as it rises up the condenser. The jacket is full of water during the process so the heat of condensation can be transferred to the water. A completely filled condenser provides maximum cooling therefore allowing for maximum recovery of the purified liquid during distillation.

If water enters from the top, it causes the water at the lower end will always be warmer that can affect the efficiency of distillation.

2. Atmospheric pressure and boiling points are directly proportional which means that increase in atmospheric pressure would increase the boiling point of a solution. Therefore, a reduction in atmospheric pressure will cause a decrease in the boiling point of ethyl acetate.

3.

A Vigreux column is a glass distillation column, a fractionating column, used for fractional distillation. The inside of the column contains a series of downward-pointing 'spikes' which serve to dramatically increase the surface area without increasing the length of the condenser. This column condenses the distilling vapor as it passes through the column. The repeated vaporization and condensation processes that occurs as the condensate passes up the column allows for a more accurate distillation of mixtures.

It is important to keep the uniform temperature gradient in a fractionating column because this factor controls the precision of separation. Temperature gradient of a fractionating column can defined as a change in temperature in regards to the top being cooler and the bottom being hotter.