Irreversible reactions
Generally we found that once reactants are converted into product then the product cannot be again converted into reactants. So, irreversible reactions are those reactions in which the products manufactured by reaction in reactants cannot be converted back in reactants. These reactions are represented by putting single headed arrow (
) between reactants and products. For example,
The cooking gas (L.P.G.) used in the kitchen is mainly butane gas, which on combustion with air produces carbon dioxide and water as products.
C4H10(g) + O2 (g) CO2(g) + H2O (g) + Heat
In this reaction we cannot combine carbon dioxide and water to remanufacture butane so this is an irreversible reaction.
Reversible reactions
In these reactions the products manufactured can be again converted into the reactants from which they are formed. These reactions are represented by putting a double headed arrow (
) between reactants and products. For example,
1) Nitrogen gas can react with hydrogen gas to produce ammonia. This reaction can be shown as:
N2 (g) +3H2 (g) 2NH3 (g)
However it is found that as soon as ammonia gas is produced in the above reaction it starts breaking into nitrogen gas and hydrogen gas in the reverse direction as given below:
2NH3 (g) N2 (g) +3H2 (g)
Now because the reaction is taking place in both the directions i.e. in forward and in backward direction so we conclude that this reaction is reversible in nature, and it can be represented as:
N2 (g) +3H2 (g) 2NH3 (g)
2) Dehydration of hydrated salt of copper sulphate is also an example of reversible reaction. The chemical formula of hydrated copper sulphate is CuSO4.5H2O. In the formula of copper sulphate 5 molecules of water of crystallization are present. Due to the presence the water molecules in copper sulphate crystals its colour is blue
When we heat the crystals of copper sulphate then the 5 molecules of water evaporates and the blue crystals of copper sulphate changes into white colour as given below:
However this reaction can be reversed by allowing the white crystals of copper sulphate to cool down. On cooling the crystals of copper sulphate will absorb the water vapors present in air and blue colour will reappear.
So, this reaction can be represented as:
3) The process of transportation of oxygen gas by protein hemoglobin present in blood in our body is also reversible reaction. When we breathe in oxygen in our body then the hemoglobin of blood attaches the oxygen gas with itself to make a complex called oxyhemoglobin in our body. Then this oxygenated blood reaches every part of body. There this oxyhemoglobin complex breaks down and oxygen is given to body tissues and cells.
Oxygen + Hemoglobin Oxyhemoglobin
In this way we conclude that transportation of oxygen in our body is a reversible reaction.
Test your understanding and answer these questions:
- What are reversible reactions? Give example.
- What are irreversible reactions? Give example.