Why is stoichiometry important in baking?
If you want to get the right amount of the product, you need to measure the specific amounts of each reactant (ingredient) as given in the recipe, such as flour and sugar. If you change the amount of any of your reactants, the product will not turn out as expected.
The same thing is true for chemical reactions. Stoichiometry tells us how much of each reactant is required to obtain the desired amount of product.