This video lecture from Reaction Kinetics (F.Sc. first year Chemistry) covers the effect of nature and concentration of reactants on the rate of a chemical reaction. The nature of reactants includes the phase, number of bonds and complexity of molecule, arrangement of valence electrons and type of bonding in the reacting specie. All factors play a vital role in altering the rate of reaction. The effect of concentration of reactants has already been illustrated in the rate law and order of reaction through the law of active masses which states that rate of reaction is a direct function of the active masses (or concentrations) of the reacting molecules in the rate determining step. 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.