Sorry, I had a network problem...

Could you go over #2 & #3 from summer 2009 problem set #11?
Thanks

#2 is an algebra problem.
NO₂(g) + 2 H₂S(g) <=> NS₂(g) + 2 H₂O(g)
ΔG_rxn = (1)(-ΔG_f(NO₂(g))) + (2)(-ΔG_f(H₂S(g))) + (1)(ΔG_f(NS₂(g))) + (2)(ΔG_f(H₂O(g)))
From the problem and the tables in your book, you know all of the values in this equation except ΔG_f(NS₂(g)). Plug in and solve for ΔG_f(NS₂(g)).

#3 has a couple parts. First, write out a balanced net ionic equation, it will be difficult to handle this problem if you use a full molecular equation. This is just a backwards K_sp process, so the net ionic equation is:
Pb²⁺(aq) + 2 Cl^-(aq) <=> PbCl₂(s)
Calculate ΔG for this reaction at standard conditions from tabulated values. {I don't have a book with tabulated thermodynamic values handy so I can't calculate an exact value for you...} Once you know ΔG^o, plug in to calculate under non-standard conditions.

ΔG = ΔG^o + RTlnQ

Q = 1 / {[Pb²⁺][Cl^-]²}

Given the numbers in the problem, the correction term {RTlnQ} will probably only be a few kJ/mol. Remember to use kelvin temperatures and be consistent with kJ and J.