The rate of a reaction is a function of temperature (through the rate constant) and concentration.A zero-order reaction has a constant rate, which is independent of the reactant's concentrations. Thus the rate law is:
rate_A = kCoA = k
where k has the units of M(sec-1). In other words, a zero-order reaction has a rate law in which the sum of the exponents is equal to zero. An increase in temperature or a decrease in in temperature is the only factor that can change the rate of a zero-order reaction. In addition, a reaction is zero order if concentration data are plotted versus time and the result is a straight line. The slope of this resulting line is the negative of the zero order rate constant k.