Stoichiometry is the calculation of reactants and products in chemical reactions. Heterogeneous catalysis are catalysts whose phase differs from that of the reactants or products. Heterogeneous catalysts act in a different phase than the reactants. The ratio of the products can be controlled by the stoichiometry of the reactants. The ratio of the products can be controlled by changing the stoichiometry of the reactants. Heterogeneous catalysis has the catalyst in a different phase from the reactants. The arrangement of solvent molecules depends on the charge distribution on the reactants. This product binds tightly to the metal, preventing it from reacting with additional carbonyl reactants. Contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. This treatment requires measurement of equilibrium concentrations of reactants and products. Polymer chain length depends on the ratio of reactants. The process consists of two main equilibrium reactions, with incomplete conversion of the reactants. The concentration of reactants and products in autocatalytic reactions follow the logistic function. Reaction rates are highly dependent on the conformation of the reactants. The pH of the neutralized solution depends on the acid strength of the reactants.