Atomic mass of Oxygen is 16 and atomic number is 8. What is the mass in grams of 2 moles of oxygen gas?

Oxygen gas exists as a diatomic molecule, ${\text{O}}_2$.The molar mass of oxygen gas (${\text{O}}_2$) is calculated as:
$$\text{Molar Mass}=2\times 16\text{g/mol}=32\text{g/mol}$$
The mass of $2\text{moles}$ of oxygen gas is:
$$\text{Mass}=\text{Number of moles}\times \text{Molar mass}$$
$$\text{Mass}=2\times 32=64\text{g}$$