To calculate the mass of O2 in 2.047 moles, we need to multiply the number of moles by the molar mass of O2. The molar mass of O2 is 32 g/mol, which means that one mole of O2 weighs 32 grams.

Number of grams = Number of moles × Molar mass

Number of grams = 2.047 moles × 32 g/mol

Number of grams = 65.54 g

Therefore, there are 65.54 grams in 2.047 moles of O2.