[candiishop]

Hi again, I have trouble answering this question.

1) Calculate the reaction free energy of 2H2(g) + O2(g) <----->  2H2O(g)
when the concentrations are 0.026 mol L-1 (H2), 0.33 mol L-1 (O2), and 1.84 mol L-1 (H2O), and the temperature is 700K. For this reaction Kc = 45 at 700 K.

A) 8.1kJ
B) 14.7 kJ
C) 34.3 kJ
D) 3.5 kJ

2) Which one of the following is a correct formation reaction?

A) C(diamond) ------> C(graphite)

B) H2(g) + O(g) -------->  H2O(l)

C) C(graphite) + 4H(g) ------->  CH4(g)

D) 6C(graphite) + 6H2O(s) --------> C6H12O6(s)

E) 2C(graphite) + 3H2(g) + ½O2(g) ------->  C2H5OH(l)  

I think the answer is A for question 2. I'm not sure :S

Many thanks

[Yggdrasil]

For 1)

You can calculate the standard change in free energy (deltaG^o) from K_c.  Then you can use the standard change in free energy to calculate the change in free energy using the concentrations given.  The equations you need should be in your textbook (I'm too lazy to write them out now)

For 2)
The standard state of carbon is graphite, so (a) isn't correct since the reactant is not in its standard elemental state.