The word ‘stoichiometry’ is derived from two Greek words - stoicheion (meaning element) and metron (meaning measure). Stoichiometry, thus, deals with the calculation of masses (sometimes volumes also) of the reactants and the products involved in a chemical reaction. Before understanding how to calculate the amounts of reactants required or those produced in a chemical reaction, let us study what information is available from the balanced chemical equation of a given reaction. Let us consider the combustion of methane. A balanced equation for this reaction is as given below:
CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O(g)
The above balance reaction gives the following information:
1. For every 1 mole of CH4, 2 mole of O2 will be required to produce 1 mole of CO2 and 2 moles of H2O. This signifies Mole – Mole relation
2. For every 16 gms of CH4, 64 gms of O2 will be required to produce 44 gms of CO2 and 36 gms of H2O this signifies Mass – Mass relation
3. Ratio of moles of CO2 : H2O at any time = 1 : 2
4. There will be no change in total mass of all reactants and products at any time for any chemical reaction.
