Question

In the PE diagram, what is the RDS (rate determining step) for the forward reaction? Enter letters or numbers in the following format: X-Y, 7-8, or X-7

Answer 1

the above example step 3 i.e $B\rightarrow C$ is the rate determining step because as  the rate is slow, so rate constant( k) value will be low

and according to Arrhenius theory if k is less high activation energy (E_a) is required

$k= Ae^{-E_{a}/RT}$

where T is temperature at which the reaction is occurring

R = universal gas constant

A =pre exponential factor

as seen in the PE from going B to C huge activation energy is required which means more energy has to be supplied to push the reaction in the forward reaction so it is the rate determining step