In: Chemistry
The rate consant for the reaction
I+I+Ar---->I2+Ar
is 0.59 x 1016
cm6mol-2s-1 at 293K. What is the
half-life of I is [I]o= 2 x 10-5 mol
L-1 and [Ar]= 5 x 10-3 mol
L-1?
I+I+Ar→I2+Ar
Rate=k[I]^2 [Ar]
As Ar is constant ,so the rxn is independent of concentration of Ar,[Ar]
Can be represented as I+I→I2
rate =k’ [I]^2
k’=k*[Ar]
It is second order with respect to I,
So integrated rate law,
t(1/2) =1/k[I]o
given, k’=rate constant=0.59*10^16 cm6 mol-2 s-1=k*[Ar]
k=k’/[Ar]=( 0.59*10^16 cm6 mol-2 s-1)/(5*10^-3 mol/L*1000cm^3/L)
=( 0.59*10^16 cm6 mol-2 s-1)/(5 mol/cm^3)
=0.118 *10 ^16 cm3 mol-1 s-1
[I]o=2*10^-5 mol/L=2*10^-5 mol/L*1000cm3/L=2*10^-2 mol/cm
t(1/2) =1/k[I]o
=1/(0.118* 10^16 cm3 mol-1 s-1 )*( 2*10^-2 mol/cm3)
=8.47 *10^14 s
t(1/2) =8.47 *10^14 s