How we get to know that 2 moles of NH3 gives out N2 and 3 moles of H2 in the presence of platinum is a zero order even if the 2 moles are present  which gives the sum of power 2 as per the definition of order of the reaction but how it is zero and as well as  how it is not depending on the concentration of the reactants ?

Dear dubey.bharat7@gmail.com

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The order of a reaction cannot be deduced from the chemical equation of the reaction. Reactions in heterogenous system usually follow zero order kinetics. In such a system the reactants are adsorbed on the surface of a solid catalyst. At low concentrations of the reactant, the rate of the reaction depends on the fraction of the surface covered by the reactant. However, at higher concentrations the surface of the catalyst becomes fully covered and any further increase in the concentration of the reactants does not affect the rate of the reaction.

So depending upon concentration we can come to know whether the reaction is first order or zero order. With the help of stoichiometriy we can come to know the exact number of moles produced by NH₃.

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Topperlearning Team.