[lilmul123]

It's been a while since I've done questions like these.  We're currently in the review stage for the AP Chemistry exam, and my mind is so  disorganized, I can't remember how to do these.  Er anyway...

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Consider the reaction below.

H2(g) + Cl2(g) 2 HCl(g)
(a) Calculate H°, S°, G°, and K (at 298 K) using data in Appendix 4.

I have H S and G: -184, 20, and -190 kJ/mol respectively.  Now I need to find K.  The only equation I have on an equation sheet is (delta)G = -RT ln(K).  When I use this equation to find K, it's extremely large.  So large that it gives me an overflow error on my calculator.

This last question, I have the faintest idea on how to do it.

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Consider the following reaction.

H2O(g) + Cl2O(g) 2 HOCl(g) K298 = 0.090
Use the data below for Cl2O(g).

G°f = 97.9 kJ/mol
H°f = 80.3 kJ/mol
S° = 266.1 J/Kmol

d. Estimate H°f and S° for HOCl(g).
e. Estimate the value of K at 500. K.
f. Calculate G at 25°C when PH2O = 17 torr, PCl2O = 2.8 torr, and PHOCl = 0.10 torr.

Honestly, I'd love to share my method, but I honestly haven't a clue.  since it's at equilibrium (doesnt show up on this page, but the equilibrium sign is there on my homework site), so I figured that i needed to find when G = 0.  But...that didn't really help at all.  Also, I don't remember how to calculate G at all using pressures.  Sorry if I'm asking too much, but I really need to understand this.  the AP chem exam is May 15th!

[enahs]

I have H S and G: -184, 20, and -190 kJ/mol respectively.  Now I need to find K.  The only equation I have on an equation sheet is (delta)G = -RT ln(K).  When I use this equation to find K, it's extremely large.  So large that it gives me an overflow error on my calculator.

You are taking the ln of a negative number, no no. You want to take the antilog to solve for K. or e^(?G/RT) = K


The other question I can not really make out what those superscripts are. Take it out of the code bracket, that just makes it hard to read. I could copy and paste, but that is too much work

[allanf]

I don't remember how to calculate G at all using pressures.

If you recall ?G = ?G° + RT ln(K)

K constants can be defined in terms of pressure or concentration.  This makes sense if you think back to the ideal gas law:
PV = nRT -> P = (n/V)RT = cRT

So pressure is proportional to concentration (at least in the gas phase).  That is to say, the K constant for this reaction in terms of pressures would be the same form as it would in terms of concentrations:
products over reactants.