I managed to get the correct answer, however I don't know if my logic was sound. 1. The problem statement, all variables and given/known data At ordinary temperature nitrogen tetroxide is partially dissociated (broken up) into nitrogen oxide. Into an evacuated flask of 250 cm^3 volume, 0.86g of liquid N2O4 at 0 C is introduced. When the temperature in the bulb has risen to 27 C the liquid has all vaporized and the pressure is 1120mm of mercury. What percent of the nitrogen tetroxide has dissociated in this process? 2. Relevant equations PV=nRT 3. The attempt at a solution First thing, I decided to convert .86 grams of N2O4 to moles. Found it to be 0.00935 moles Then, using PV=nRT, determined the total number of "gas" moles in the flask at 27 C (300K). Found this to be 0.0149 moles. 0.0149 - 0.00935 = 0.00555 moles added ? (0.00555/0.00935) x 100% = 59.3% Initially this all made sense to me, but now I go back and read the question, it says all my liquid was vaporized (consequently expanded into the flask). So shouldn't my %dissociation be 100%? In addition, if my method was correct, what does the 0.00555 actually mean? Is that the amount of N2O4 that didn't/did turn into gas? Any help appreciated.