1. Find the molar mass of oxygen (O2):

* Oxygen exists as a diatomic molecule (O2).

* The atomic mass of oxygen is approximately 16 g/mol.

* The molar mass of O2 is 16 g/mol * 2 = 32 g/mol

2. Use the formula: mass = moles x molar mass

* mass = 0.05 mol * 32 g/mol

* mass = 1.6 g

Therefore, the mass of 0.05 moles of oxygen is 1.6 grams.