Half-life for first-order reaction

Rate Laws Experimental measurement of the rate leads to the rate law for the reaction, which expresses the rate in terms of the rate constant and the concentrations of the reactants. The dependence of rate on concentrations gives the order of a reaction. A reaction can be described as zero order if the rate does not depend on the concentration of the reactant, or first order if it depends on the reactant raised to the first power. Higher orders and fractional orders are also known. An important characteristic of reaction rates is the time required for the concentration of a reactant to decrease to half of its initial concentration, called the half-life. For first-order reactions, the half-hfe is independent of the initial concentration. 

FIGURE 4,5 Thermal stability of organic peroxides as indicated by time for decomposition of 50% of the original charge (half-life for first-order reaction). (Data from Wallace and Tiernan Company, Lucidol Organic Peroxides, Lucidol Division, Wallace and Tiernan, Buffalo, NY, 1968.)... 

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