Question

Please help determine the rate law for the overall reaction (where the overall rate constant is represented as? consider the following mechanism
step 1: 2a ----> b+c slow
step 2: b+c ---> e fast
______________________
overall: 2a ----> e
determine the rate law for the overall reaction (where the overall rate constant is represented as k
rate=______
please explain how you got the answer and show steps

Answer 1

The overall rate of a reaction is determined by the rate-determining step.
As the reaction can only happen as quickly as the rate-determining step, this is the slowest step.
1. Determine the slowest reaction: 2a ----> b+c
2. Identify molecularity: bimolecular (there are two reactants)
3. Write rate law: rate = k[a]^2
The exponents for the rate law of elementary steps are determined by molecularity.
I hope this explained it!

Answer 2

For the answer to the question above, The rate law for the slow step is: rate=k [C] [D] 
Since [C] is an intermediate, we need to substitute it using equilibrium step. 

We know equilibrium means the rate of forwarding reaction = rate of reverse reaction. 
so, k[A] = k[B] [C] this shows the equilibrium. 

Then solve for [C] to get: k[A]/k[B]= [C]. 
Now, you simply substitute in the initial rate equation you got from the slow step to get: 

rate= k(slow) {k[A]/[B]} x [D] 

So I think the answer here is = k{ [A] [D] } / [B].