In: Chemistry
The activation energy for the isomerization of methyl isonitrile is 160KJ/Mol.
1) Calculate the fraction of methyl isonitrile molecules that have an energy of 160.0 kJ or greater at 508 K .
2) Calculate this fraction for a temperature of 525 K .
3) What is the ratio of the fraction at 525 K to that at 508 K ?
please help!
Answer : The effect of temperature on rate of reaction and hence
on rate constant k is given by Arrhenius equation:
k = Ae^-(Ea/RT)
where A is called pre-exponential factor..
Ea is activation enrgy ..
T is absolute temperature
R is gas constant = 8.314 j/K/mole
and k is rate constant..
the factor e^(-Ea/RT) gives the fraction of molecules having energy
equal to or greater than the activation enrgy Ea..
suppose the fraction is represented as x then :
x = e^(-Ea/RT)
taking log both sides..
ln x = -Ea/RT
converting ln to log ...multiply by 2.303
2.303 X log x = -Ea/RT
log x = -Ea/(2.303RT)
Now , On the basis of this we can calculate the all requiered things
1] LogX = - 160000 / 2.303 * 8.314 * 508
log X = - 160000/ 9726.74814 = -16.4494
X = 3.55 * 10-17
Hence, the fraction of methyl isonitrile molecules is 3.55 * 10-17
2] Similarly this one is solve at 525 K
Log X = - 160000 / 2.303 * 8.314 * 525
= - 160000 / 10052.2496 = - 15.9168
X = 1.211 * 10-16
Hecne the fraction is comes out to be 1.211 * 10-16
3 ] Now the ratio between 525K / 508 K = 1.211 * 10-16 / 3.55 * 10-17
= 3.41
Hecne the ratio of fraction is 3.4
Thank you :)