Mole ratio is the proportional amount of moles of two or more compounds in a chemical reaction, and this concept is widely used in Stoichiometry, since in this type of matter we have to be comparing initial amount of reactant and final amount of product, usually, we have to convert grams of mass into moles of the compound, and when we have to compare the number of moles of different compounds, we use mole ratio, as we can see in the example below:
A + 2 B -> X
The mole ratio between A and B is 1:2, therefore if we have 3 moles of A in the reaction, we would have 6 moles of B, and with that concept in mind, we can find the mass asked in any question.
In this process, we can have the theoretical yield of a reaction, which is how much of the product is produced from the initial amount of reactant
We have two oversimplified reactions that take in account mole ratio:
1. Formation of Ammonia:
N2 + 3 H2 -> 2 NH3, here we have the following mole ratios:
1 N2 = 3 H2
1 N2 = 2 NH3
3 H2 = 2 NH3
2. Burning of Octane, which is fuel:
2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O
The mole ratios are:
2 C8H18 = 25 O2
2 C8H18 = 16 CO2
2 C8H18 = 18 H2O
25 O2 = 16 CO2
25 O2 = 18 H2O
16 CO2 = 18 H2O
Limiting and excess reactants are, as the name already implies, the reactant the will limit the amount of the other reactant undergoing the reaction, and this is found through mole ratio. The excess reactant is the reactant that will not totally react, but it will have some of it left without undergoing the reaction