The Rate Law: Concentration and Time

The rate law for a chemical reaction relates the reaction rate with the concentrations or partial pressures of the reactants.

A first-order reaction depends on the concentration of one reactant, and the rate law is: $r=-\frac{dA}{dt}=k[A]$ .

A second-order reaction is second-order in only one reactant, or first-order in two reactants.

A zero-order reaction has a constant rate that is independent of the concentration of the reactant(s); the rate law is simply $rate=k$ .

The integrated rate laws derive from calculus, and they relate the concentrations of reactants with time.

The half-life of a reaction is the amount of time it takes for the concentration of a reactant to decrease to one-half of its initial value.