The flow chart shows a method of liquefying air: air → fine filtering → pass through potassium hydroxide → pass through anhydrous calcium chloride → compression and cooling → liquid air. The table shows the boiling points of some of the gases in air.

1. aName the substance that is removed when air passes through potassium hydroxide. [1]
2. bName the substance that is removed when air passes through anhydrous calcium chloride. [1]
3. cExplain by reference to the behaviour of molecules why compression and cooling help to liquefy air. [2]
4. dName two substances that will remain as gases when air is cooled to −200 °C. [1]
5. eName the method by which the rest of the components of liquid air will be separated. [1]

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