This video lecture from Reaction Kinetics (F.Sc. first year Chemistry) covers the half life period of a chemical reaction. In chemistry, half life period is defined in terms of the changes in concentration so if the half life is x seconds, the concentration becomes one half in x seconds. A formulae has been derived to determine the concentration at any time, given the half life period. For higher order reactions, half life is not constant and is a function of order of reaction, rate constant and the concentration of reactants. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.