Equations for elementary reactions show the actual molecules, atoms, and ions that react on a molecular level. Protein or protein-based molecules that speed up chemical reactions occurring in living things. Without enzymes life as we know it would be impossible. Compare with zero order reaction and second order reaction . The sum of concentration exponents in the rate law for a first order reaction is one.
Many radioactive decays are first order reactions.
The half life of a reaction is the time required for the amount of reactant to drop to one half its initial value. A highly reactive substance that forms and then reacts further during the conversion of reactants to products in a chemical reaction. Intermediates never appear as products in the chemical equation for a net chemical reaction . The order of a reaction is the sum of concentration exponents in the rate law for the reaction. Noninteger orders are possible.