1. The problem statement, all variables and given/known data A flask with a volume of 2.70 L, provided with a stopcock, contains ethane gas (C_2 H_6) at a temperature of 297 K and atmospheric pressure 1.01×10^5 Pa. The molar mass of ethane is 30.1 g/mol. The system is warmed to a temperature of 396 K, with the stopcock open to the atmosphere. The stopcock is then closed, and the flask cooled to its original temperature. 1-What is the final pressure of the ethane in the flask? 2-Find the mass of ethane remaining in the flask. Use 8.31 J/(mol * K) for the ideal gas constant. 2. Relevant equations pV=nRT M=n * mm 3. The attempt at a solution I used pV=nRT to get the final pressure to be 7.6 * 10^4 Pa for part one, but when I use this to work out the answer to part two I keep getting it wrong. I used n = (pV)/(RT) and then M = n * mm so M = (30.1pV)/(RT) The advice that was given was that You have to watch the units, do I have to convert Pa to atm or something, what am I missing?