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What is Half-Life time of a reaction ?Derive the equation of Half -Life time(t_((1)/(2))) for zero order reaction.

Answer»

Solution :Half-LIFE time:The half-life of a reaction is the time in which the concentration of a reactant is reduced to one half of its intial concentration it is called half life and REPRESENTED as `(t_((1)/(2)))` .
To derive `t_((1)/(2))` EQUATION of zero -order reaction:
For a zero order reaction,rate constant (k) is given by following equation .
`k=([R]_(0)-[R])/(t)`.........(a)
Where t=half life time =`t_((1)/(2))`.....(i)
`[R]_(0)` =The concentration of reactant
at t=0 time....(ii)
[R]=The concentration of reactant at `t_((1)/(2))` time
=`(1)/(2)` initial concentration `[R]_(0)`
`therefore [R]=(1)/(2)[R]_(0)`......(iii)
Put these value in (a)
`k=([R]_(0)-(1)/(2)[R]_(0))/(t_(1)/(2))`
`therefore k=(1[R]_(0))/(2xxt_((1)/(2)))` and
`t_((1)/(2))=([R]_(0))/(2k)` (half life of zro ordr reaction)
It is clear that `t_((1)/(2))` for a zero order reaction is directly proportional to the inital concentration of the reactants and iversely proportional to the rate constant.


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