Why must a chemical equation be balanced before you can determine mole ratios

Calculate the number of moles for each element. n=m/M Then compare, and which ever one is lowest is the limiting reactant because no more products can form without one or the other.

A chemical equation must be balanced before you can determine the mole ratio due to the law of conservation of mass ... you cannot get more product than the reactant you feed into the reaction and in turn you cannot get less product than the reactant you put in. You must have the same going in as you have coming out ...

With out balancing the equation this law would not be met and you would not be receiving accurate calculations.