Separating gases(chemical earth) (1 Viewer)

[WEMG]

I am doing my dot points at the moment and I am not sure how fractional condesation works, my text book only explained liquefaction and fractional distillation.
I just need someone to explain to me how fractional condensation works for separating gases.

 

[adomad]

for example, say you have carbon dioxide and oxygen in a container. the melting point of co2 is -56.57 C (from google) and oxygen is -218.4 C. if we drop the temp to -60 C, all the co2 will become liquid and gaseous oxygen will remain in the container. i haven't heard of this process but if it did exist, that is how it would be done (arrogant much )

i have learn about zeolite sieves. this is used to remove oxygen from air and results in a really high purity. this uses some thing called a zeolite crystal which holds other gasses in the air and lets only oxygen through.

Also, there is something called cryogenic air separation. this utilises the different MP of gasses to separate them (something like fractional condensation). this process turns the gas into liquid. so for the example of co2 and o2, it will cool the gases until it is -230 C, it will then slowly heat the liquid and since the o2 has the lower mp, it will turn into a gas first. this gas is collected and the liquid co2 remains at the bottom of the fraction.

hope this helps. just a note: i never got a question asking for the separation of gases, only stuff on gravimetric analysis and how to separate solids from liquids

 

[brenton1987]

I am doing my dot points at the moment and I am not sure how fractional condesation works, my text book only explained liquefaction and fractional distillation.
I just need someone to explain to me how fractional condensation works for separating gases.

Say you wanted to liquify nitrogen and oxygen from the air. Dry air is composed of nitrogen, oxygen, argon and carbon dioxide plus traces of other gases. Nitrogen condenses at 77.36 K, oxygen at 90.20 K, argon at 87.30 K and carbon dioxide at 216.6 K. The order of condensation will be carbon dioxide, oxygen, argon, nitrogen.

Gay-Lussac's Law states that "The pressure of a fixed mass and fixed volume of a gas is directly proportional to the gas's temperature." This is because the temperature of a substance is a measure of the average kinetic energy of the particles of the substance. As the kinetic energy energy increases the particles collide with the container more rapidly which exerts an increased pressure.

A sample of gas is compressed resulting in a hot compressed gas. This gas goes through a heat exchanger to give a cold compressed gas. The gas is then decompressed to its original pressure which cools it even further. The cycle is repeated until each constituent gas eventually condenses to the liquid.

Usually all of the gases are condensed at once and seperated by distillation.