In a combustion reaction of C3H8 + 5O2 = 3CO2 + 4H2O, how do you know that the first compounds will produce the nuber of what they did? . Also how do you know that this 2Ca + O2= 2CaO?
To balance chemical equations, you should just remember that the number of atoms of an element in the reactant side must be equal to the number of atoms of the same element in the product side. The order of the substances doesn't matter. What is important that the equation balances.
