1. The problem statement, all variables and given/known data Which of the following equilibria is least affected by a change in the volume of the system? A. 2 C (s) + O2 (g) = 2 CO (g) B. 2 NO2 (g) = N2O4 (g) C. H2 (g) + S (l) = H2S (g) D. H2O (l) = H2O (g) E. 2 NO (g) + Cl2 (g) = 2 NOCl (g) 2. Relevant equations N/A 3. The attempt at a solution I know the answer is C, but I don't know why. I thought maybe it had something to do with the number of moles on each side of the reaction. As volume decreases, pressure increases, and the reactions will favor the side with the least number of moles. I know this is true, but perhaps it doesn't apply? This is a sample exam problem, and any hints as to how I should approach it would be greatly appreciated.