Using potassium hydroxide it is possible to separate carbon dioxide from a mixture of gases. Potassium hydroxide reacts with carbon dioxide to form potassium hydrogen carbonate, this further reacts with aqueous potassium hydroxide to give potassium carbonate, though the second reaction does not involve carbon dioxide. The chemical reactions that take place here are:
KOH (aq) + CO2 (g) ---> KHCO3 (aq)
KHCO3 (aq) + KOH (aq) ---> K2CO3 (aq) + H2O (aq)
Heated copper is used to absorb oxygen from the mixture of gases. Oxygen reacts with copper to form copper oxide.
The chemical reaction that takes place here is:
2 Cu(s) + O2 (g) --> 2 CuO(s)
Therefore when the mixture of gases is passed through potassium hydroxide and heated copper, carbon dioxide and oxygen are removed.