Drawbacks of a chemical equation:
1) A chemical equation doesnot give information about the physical states of the reactants and products.
2) It doesnot give any information regarding the speed of the reaction
3) It doesnot tell whether the reaction is complete or not.
4) It doesnot convey the conditions (temperature, pressure etc.) at which the reaction takes place.
5) It doesnot tell about the actual amount of the reactants consumed and products formed.