Half Life of a Reaction – Class 12 | Chapter – 4 | Chemistry Short Notes Series PDF for NEET & JEE

Half Life of a Reaction: The half-life of a reaction is the time it takes for half of the reactants to be consumed or for the concentration of the reactants to decrease by half. It is a measure of the rate of a reaction and can be used to determine the reaction order and rate constant.

Half Life of a Reaction

The half-life of a reaction depends on the reaction order, which is the exponent to which the concentration of the reactants is raised in the rate law. For example, a first-order reaction has a constant rate that is proportional to the concentration of a single reactant, and its half-life is independent of the initial concentration of the reactant. In contrast, a second-order reaction has a rate that is proportional to the product of the concentrations of two reactants, and its half-life depends on the initial concentrations of the reactants.

The half-life can be calculated using the following equation:

t1/2 = (ln 2) / k

where t1/2 is the half-life, ln 2 is the natural logarithm of 2 (approximately 0.693), and k is the rate constant of the reaction.

It is important to note that the half-life is a characteristic property of a particular reaction at a specific temperature and can vary with changes in temperature or other reaction conditions.


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By Team Learning Mantras