How many grams of o2 are in a 5.0 mol of the oxygen gas?

We are tasked to find the amount of O2 in grams given only the number of moles of oxygen gas. To solve the problem, we need first to calculate the molecular weight of oxygen. Based on the periodic table, elemental oxygen has a molecular weight of 16 g/mol. Thus its molecular weight is,
O2=16.0g/mol (2)=32 g/mol

To solve for the amount of compound oxygen in grams, we have,
O2 (g)=5 mol x 32 g/mol =160 g.

This cancel out the mols both in the numerator and denominator leaving only the g as a unit. Therefore, 5 mols of oxygen is equal to 160 g of oxygen.