Stoichiometry is a branch of chemistry that deals with the calculation of reactants and products in chemical reactions. It is based on the conservation of mass, which means that the total mass of the reactants must equal the total mass of the products. By using balanced chemical equations, chemists can determine the proportions of substances involved in a reaction. In stoichiometry, coefficients in a balanced equation represent the ratio of moles of each substance. This allows for the conversion between grams, moles, and molecules, enabling scientists to predict how much of a product can be formed from given amounts of reactants.