Neet Solved Paper 2015 Question 19
Question: When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is
Options:
A) zero
B) first
C) second
D) more than zero but less than first
Show Answer
Answer:
Correct Answer: B
Solution:
For a zero order reaction $ {{t} _{1/2}} $ is directly proportional to the initial concentration of the reactant
$ {{[R]}_0} $ $ {{t} _{1/2}}\propto {{[R]}_0} $
For a first order reaction $ k=\frac{2.303}{t}\log \frac{{{[R]}_0}}{[R]}at,{{t} _{1/2}},[R]=\frac{{{[R]}_0}}{2} $
So, the above equation becomes $ K=\frac{2.303}{{{t} _{1/2}}}\log \frac{{{[R]}_0}}{{{[R]}_0}/2} $ $ {{t} _{1/2}}=\frac{2.303}{K}=\log 2=\frac{2.303}{K}\times .3010 $ $ {{t} _{1/2}}=\frac{.693}{k} $
i.e. half-life period is independent of initial concentration of a reactant.
