The molecular weight of CH4 is 16 g/mol (12 for Carbon + 1 for each Hydrogen). Therefore, the mass of 2 moles of CH4 can be calculated as follows:

• Number of moles = 2
• Molar mass of CH4 = 16 g/mol
• Mass = Number of moles x Molar mass
• Mass = 2 mol x 16 g/mol
• Mass = 32 g

Therefore, the mass of 2 moles of CH4 is 32 grams.