ICSE Class 8 Answered

A chemical equation has its own limitations. They do not provide information about: 

1. The physical state of reactants and products Hence, the symbols ‘s’ for solid, ‘l’ for liquid, ‘g’ for gas and ‘vap’ for vapour are added. 
2. Conditions such as temperature, pressure and catalyst affecting the reaction 
3. Concentration of reactants and products Hence, in some cases, for dilute ‘dil.’ and for concentrated ‘conc.’ are added. 
4. The nature of the chemical reaction; whether it is reversible or irreversible reaction. 
5. Speed of the reaction 
6. Heat changes accompanying the reaction; whether heat is given out or absorbed 
7. Time taken for completion of the reaction A reaction may or may not be complete, and the equation does not reveal it.