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NCERT Class XII Chemistry
Chapter - Chemical Kinetics
Questions with Solutions

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Question : 39
Total: 39
The activation energy for the reaction 2HI(g)→H2(g)+I2(g) is 209.5 kJ mol‌–1 at 581 K. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy.
Solution:  
Fraction of molecules having energy equal to or greater thanactivation energy is given as
x=
n
N
=e−Ea∕RT
∴ln‌x=−
Ea
RT

or, log‌x=−
Ea
2.303RT

or, log‌x=−
209.5×103
2.303×8.314×581

=−18.8323
∴‌‌x= Antilog (−18.8323)
=1.471 ×10−19
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