GCSE Chemistry

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kagawa88
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#1
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#1
Air is a mixture of gases and contains various pollutants . The gases are useful and can be seperated by fractional distillation of liquid air . The table gives information about some of the gases in air
to seperate these gases :
the air is filtered
water is removed first
carbon dioixde is then removed by absorption
the gases remaining are compressed and cooled to -200°C
Water vapour and carbon dioxide are removed before the gases are compressed and cooled.Use the information in the table to suggest why.

I know the answer that at -200 degrees C they are solid and block pipes. But I do not understand why. It says the melting point of Water vapour is 0 and -78.5 for carbon dioxide so surely they are liquid. If you cooled beyond this temperature they are solid?
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shwansalah
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#2
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(Original post by kagawa88)
Air is a mixture of gases and contains various pollutants . The gases are useful and can be seperated by fractional distillation of liquid air . The table gives information about some of the gases in air
to seperate these gases :
the air is filtered
water is removed first
carbon dioixde is then removed by absorption
the gases remaining are compressed and cooled to -200°C
Water vapour and carbon dioxide are removed before the gases are compressed and cooled.Use the information in the table to suggest why.

I know the answer that at -200 degrees C they are solid and block pipes. But I do not understand why. It says the melting point of Water vapour is 0 and -78.5 for carbon dioxide so surely they are liquid. If you cooled beyond this temperature they are solid?
melting point of water vapour is 0 therefore any number lower than 0 would make it a solid. Carbon dioxide's melting point is -78.5 therefore any temperature lower than that, it is a solid and will freeze. If the water was heated above 0 degrees it would be a liquid. but if it is cooled below 0 degrees, e.g -200,l it would be a solid because 0 degrees is when it starts to become a liquid because that is its MELTING POINT.
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username1530463
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Is this AQA?
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kagawa88
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#4
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#4
Yes AQA and thank youshwansalah
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