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Gernald · Mar 19, 2009, 08:36 PM

Hi all I'm studying for a test and got a stumped by this question and am not sure where to go, and I'm fairly certain it'll be on the test :eek: Anyway, whatever you can help me with would be great!

I'm looking at the decomposition of HI
2HI (g) --> H2 (g) +I2 (g)
It has a 2nd order rate law. At 700k the rate constant is 1.2x10^-3 L mol-1 s-1. If the initial concentration is [HI]0 = 0.56 mol L-1 what is [HI] after two hours.

Do I use claussius claperyon (am I even spelling that right?) ? And if I do, how do I plug it in?
I feel like an idiot, I get the ones way harder than this in like 5 seconds :(
Thanks again for any help!

Perito · Mar 20, 2009, 02:23 AM

I'm not sure how you could use Clausius-Clapeyron to describe kinetics. That's more of a chemical "phase" thing.

A second order rate law is one of the following

$R = k[a]^2$

or

$R = k[a][b]$

In this case, I would assume that it's the former, with [a] being the concentratino of [HI]. You are given the rate constant and the initial concentration.

The integrated form of the above rate law is:

$\frac1{[A]} = kt + \frac1{[A_o]}$

I think you have everything to solve the equation.