The concentration of R in the reaction; R → P ; was measured as a function of time and the following data is obtained : R mol L - 1 1 . 0 0 . 75 0 . 4 0 . 1 t min 0 . 0 0 . 05 0 . 12 0 . 18 Determine the order of reaction.

Rate can be defined as the change in the concentrations of reactants per unit time. From the given data, rate of reaction at different intervals can be calculated as : R 1 = 1 - 0 . 75 0 . 05 = 5 . R 2 = 1 - 0 . 4 0 . 12 = 5 . R 3 = 1 - 0 . 1 0 . 18 = 5 . The rate of reaction is not changing with change in concentration and hence, the given reaction is of zero order.

The rate constant of a reaction of zero order in A is 3 × 10 - 3 mol L - 1 s - 1 . How long will it take for the initial concentration of A to fall from 0 . 10 M to 0 . 075 M ?

Rate constant in a zero order can be calculated as : k = R ∘ - R t , where R ∘ is initial molar concentration of reactant and k is rate constant of the zero order reaction. t = R ∘ - R k t = 0 . 1 - 0 . 075 3 × 10 - 3 = 8 . 3 s Hence, the value of time comes out to be 8 . 3 s

Under what condition a bimolecular reaction behaves kinetically first order reaction?

In a bimolecular reaction, when the amount of one of the reactants is present in excess, the reaction is kinetically first order because the concentration of reactant present in excess does not affect the order of reaction. Hence, it does not affect the rate of reaction and such reactions are called pseudo first order reactions. Example : Hydrolysis of sucrose yielding glucose and fructose.