Chemical Kinetics Question 334
Question: The activation energy for a simple chemical reaction $ A\to B $ is $ E_{a} $ in forward direction. The activation energy for reverse reaction
Options:
A) is always double of $ E_{a} $
B) is negative of $ E_{a} $
C) is always less than $ E_{a} $
D) can be less than or more than $ E_{a} $
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Answer:
Correct Answer: D
Solution:
[d] The activation energy of reverse reaction will depend upon whether the forward reaction is exothermic or endothermic. As $ \Delta H=E_{a} $ (forward reaction)- $ E_{a} $ (backward reaction) For exothermic reaction $ \Delta H=-ve $
$ \therefore -\Delta H=E_{a}(f)-E_{a}(b) $ Or $ E_{a}( f )=E_{a}( b )-\Delta H $
$ \therefore E_{a}( f )<E_{a}( b ). $ for endothermic reaction $ \Delta H=+ve $
$ \therefore \Delta H=E_{a}(f)-E_{a}(b),or,E_{a}(f)=\Delta H+E_{a}(b) $
$ \therefore E_{a}(f)>E_{a}(b). $
