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chapter 11 #67 help happy thanksgiving! :)

Posted: Thu Nov 24, 2016 11:25 am
Question: The reaction 2HCl(g) <----> H2(g) +Cl2(g) has K=3.2 X 10^-34 at 298K. The initial partial pressures are H2, 1.0 bar; HCL, 2.0 bar; and Cl2, 3.0 bar. At equilibrium there is 1.0 mol H2(g). What is the volume of the container?

The answer solution mentions that reactants are strongly favored, it is easier to push the reaction as far to the left as possible then start from new initial conditions...what does this mean I don't understand why they have an "original" or "new initial"? thank you!

Re: chapter 11 #67 help happy thanksgiving! :)

Posted: Thu Nov 24, 2016 1:47 pm
Hi Grace,

Because Q is significantly larger than K, the reaction favors reactants, so the solutions manual assumes that you push the reaction as far left as possible. This means that all of H2 is consumed because it is the limiting reactant (based on the given partial pressures).

So because two moles of HCl are created from every one mole each of H2 and Cl2, you add 2 to the existing 2 bars of HCl and subtract one from the existing 1 bar of H2 and 1 bar of Cl2 and that's how they got the original conditions. Then you solve using ICE box like normal.

I hope that helps!
And happy Thanksgiving to you too!

Re: chapter 11 #67 help happy thanksgiving! :)

Posted: Thu Nov 24, 2016 5:18 pm
Thank you!!