Kinetics Chemistry Question [reaction mechanisms]?

Question

NO + NO => N2O2 [fast]
N2O2 + H2 => N2O + H2O [slow]
N2O + H2 => N2 + H2O [fast]
From the mechanism above, a student deduces that the rate law of the reaction is rate = k[NO]^2[H2]. The student concludes that [1] the reaction is third order and [2] the mechanism involves the simultaneous collision of two NO molecules and an H2 molecule. Are the conclusions in [1] and [2] correct?

I thought it was no but i don't think i did it right. I found the equation to be [after intermediates were taken out]: NO + NO + H2 + H2 => H2O + N2 + H2O [and it's already balanced]
i looked back at my notes, but the way my teacher did it was confusing and they were easier ones too.
is there an easier and less confusing way to do reaction mechanisms?

Answer 1

Your first conclusion is correct, but your second isn't. Since you already have the mechanism given to you, you can see that the 2nd step is the slow step. So, the rate law should be:

rate = k (N2O2) (H2)

Since N2O2 is an intermediate, it can't appear in the overall rate law, so you have to get rid of that. From the first reaction, you see that N2O2 is formed from the collision of 2 NO. So, the concentration of N2O2 is proportional to [NO]^2. That gives you the overall rate law that you had, and the overall order of the reaction is 3rd order.

Your second conclusion is incorrect because the slow step requires the collision of N2O2 and H2. The slow step is just a second order reaction.

So, you've got things pretty well in hand...Hope this helps a little...

Answer 2

The a million/2 existence is the time it takes for a million/2 of the reactant to decay. for this reason it takes sixteen minutes for it to pass 1000g -> 500g. Then yet another sixteen minutes to pass 500g -> 250g. So sixteen + sixteen is 32, so it takes 32 minutes.