There are main three types of chemical reactions with reference to oxygen and hydrogen:
1.Combination Reaction
2. Decomposition Reaction
3. Oxidation and reduction reaction
1.Combination Reaction
When two atoms react to form a compound, it is know as combination reaction.
For example: \(2 H_2 + O_2 \to 2 H_2 O\)
2. Decomposition Reaction
When a compound breaks into simple molecular substances from which it is made up of, it is know as decomposition reaction.
For example: \(2 H_2 O \to 2 H_2 + O_2\)
3. Oxidation and reduction reaction:
Oxidation:
(i) The addition of oxygen to a substance is called oxidation.
(ii) The removal of hydrogen to a substance is called oxidation.
Reduction:
(i) The addition of hydrogen to a substance is called reduction.
(ii) The removal of oxygen to a substance is called reduction.
For example: \(CuO + H_2 \to Cu + H_2 O\)
In the above reaction, copper oxide is changing to Cu. That is, oxygen is being removed from copper oxide. So, copper oxide is being reduced to copper.
In the above reaction, H2 is changing into H2O. That is , oxygen is being added to hydrogen. So, hydrogen is being oxidised to water.