Problem: A flask with a volume of 1.10L , provided with a stopcock, contains ethane gas (C2H6) at a temperature of 289K and atmospheric pressure 1.013x10^5Pa . The molar mass of ethane is 30.1g/mol. The system is warmed to a temperature of 398K, with the stopcock open to the atmosphere. The stopcock is then closed, and the flask cooled to its original temperature.
Part A: What is the final pressure of the ethane in the flask?
Part B: How many grams of ethane remaining in the flask?
Please explain your answer. I know substitution is involved so be sure to give a detailed explanation on that as well.