NEET Chemistry Chemical Kinetics Questions Solved

NEET - 2015

When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is

(a) zero

(b) first

(c) second

(d) more than zero but less than first

(b) For a zero order reaction t1/2 is directly proportional to the initial concentration of the reactant [R]0

          t1/2 [R]0

For a first order reaction

 k= 2.303/t. log[R]0/[R] at t1/2, [R] =[R]0/2

So, the above equation becomes

          K=2.303/t1/2 .log[R]0/([R]0/2)

            t1/2 = 2.303/K = log2 = 2.303/K x .3010

            t1/2 = .693/K

i.e, half life period is independent of initial concentration of a reactant

 

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