Final answer:
To rank the gases in order of increasing molar mass, methane (CH4) is the lightest gas, followed by ethane (C2H6), and then butane (C4H10).
Step-by-step explanation:
Methane (CH4) has a molar mass of 16 g/mol, ethane (C2H6) has a molar mass of 30 g/mol, and butane (C4H10) has a molar mass of 58 g/mol. To rank the gases in order of increasing molar mass, we start with the smallest molar mass and go to the largest molar mass. Therefore, the ranking would be methane (CH4) < ethane (C2H6) < butane (C4H10).