Which step would be the rate-determining step?

The entire reaction is
H2+I2→2HI
and the rate law is rate=k[H2][I2] . The overall order for this 2, but none of these steps have a molecularity of 2.
I'd appreciate some help!
The entire reaction is
and the rate law is
I'd appreciate some help!
1 Answer
Well, the first step generates
I would say that the second step is slow, but that it is due to not enough
But let's suppose it was just the second step, because it contains
r(t)=k2[I]2[H2]
However,
I2(g)k1 ⇌2I(g)
k−1
2I(g)+H2(g)k2 −−→H2I2(g)
H2I2(g)k3 −−→2HI(g)
Then if we assume the fast equilibrium approximation, we get the equilibrium expression to be:
r1(t)=k1[I2]=r−1(t)=k−1[I]2
⇒K≡k1k−1=[I]2[I2]
As a result,
[I]2=k1k−1[I2]
And this gives:
r(t)=k2k1k−1[I2][H2]
And this agrees with the proposed rate law, where