MECHANISMS: Consider the following mechanism for the reaction: Step 1: E(g) <===

Question

MECHANISMS: Consider the following mechanism for the reaction:

Step 1: E(g) <===> 3 B(g) (fast, but reversible)

Step 2: 2 B(g) -----> C(g) + D(g) (slow)

Step 3: B(g) + D(g) ------> G(g) (fast)

a) What is the overall reaction?

b) What is the rate law for the overall reaction? The order(s) might be fractions.

c) What are the intermediates in the mechanism?

d) What is the rate determining step in the mechanism?

e) What is the molecularity of each of the elementary steps?

f) What is the difference between a transition state and an intermediate?

Explanation / Answer

a)
overall reaction can be obtained by adding all the steps
E + 2B + B+D ---> 3B + C + D + G
or,
E ----> C+ G (Answer)

b)
Rate depends on slowest step
rate = k1 [B]^2 ....eqn 1
but B is intermediates. So use step 1 assuming eqiuilibrium constant for step 1 is kc
kc = [B]^3/[E]
so,
[B]^2 = kc^2/3 * [E]^2/3
put this in eqn 1
rate = k1*kc^2/3 * [E]^2/3
let k1*kc^2/3 = constant, k
rate= k*[E]^2/3
this is overall rate law

c)
Intermediates are B and D

d)
Step 2 being slowest step is the rate determining step

e)
step 1 : molecularity = 1
step 2 : molecularity = 2
step 3 : molecularity = 2

I am allowed to answer only 4 parts at a time

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