Chemical reaction and equilibrium
Here is just a little introduction to chemical reaction and equilibrium of the reaction. Chemical reaction is a process which lead to a change of reactants into products, this can be expressed as a chemical equation, for example: NaCl + H2O -> HCl + NaOH. This chemical reaction is irreversible, means that reactants can be formed from the newly formed products. However, some chemical reactions are reversible and where there are backwards and forwards reaction (products to reactants and reactants to products). One of the example of this will be shown in Haber Process.
In the case of reversible reaction like in Haber Process, a system will react an equilibrium where the backwards and forwards reaction happen at the same rate, hence amount of reactants and products stay constant. Position of this equilibrium is affected by certain factors, such as temperature and pressure, whereas the time taken to reach this equilibrium is affected by concentration, presence of catalyst, again temperature and pressure. However, the quicker the time taken to reach equilibrium does not mean it is the most efficient, as a balance between time taken and amount of yield (this depends on the position of equilibrium) need to be taken into account.