The four main categories of stoichiometry problems are mass-mass, mole-mole, mass-volume and volume-volume problems. Stoichiometry is the study of chemical changes and the relationship of the reactants to the products.
To solve any of the four types of problems, an individual first needs to make sure that the equation is balanced before proceeding. The most common type is a mass-mass problem in which an unknown mass of a reactant or product is determined through a known mass of a reactant or product. This is accomplished by converting the known mass to moles, calculating the ratio of moles of known to unknown using the coefficients of the balanced equation, and finally converting the derived number of moles of the unknown into mass.