Hello,

Chemical equilibrium is the state of a reversible reaction where the rate of the forward reaction equals the rate of the reverse reaction. While a reaction is in equilibrium the concentration of the reactants and products are constant.

There are many examples of chemical equilibrium all around you. One example is a bottle of fizzy cooldrink. In the bottle there is carbon dioxide (CO2) dissolved in the liquid. There is also CO2 gas in the space between the liquid and the cap. There is a constant movement of CO2 from the liquid to the gas phase, and from the gas phase into the liquid. However, if you look at the bottle there does not appear to be any change. The system is in equilibrium.

CO2(g)+H2O(l) ⇌ H2CO3(aq)

Without chemical equilibrium life as we know it would not be possible. Another example of equilibrium in our everyday lives goes on within our very bodies. Haemoglobin is a macromolecule that transports oxygen around our bodies. Without it we would not survive. The haemoglobin has to be able to take up oxgen, but also to release it and this is done through changes in the chemical equilibrium of this reaction in different places in our bodies.

haemoglobin(aq) + 4O2(g) ⇌ haemoglobin(O2)4(aq)

Thanku.