Final answer:
To find the grams of O₂ in a breath of air, you calculate the volume of oxygen inhaled (94.5 ml) and use the Ideal Gas Law to find moles before multiplying by O₂'s molar mass, resulting in about 0.6 grams of O₂ per breath.
Step-by-step explanation:
The air we breathe contains approximately 21% oxygen. When taking a typical breath with a volume of 450 ml (or 0.45 L), we can calculate how many grams of O₂ are inhaled. First, we calculate the volume of oxygen inhaled using the percentage of oxygen in the air:
Volume of O₂ = 21% of 450 ml = 0.21 × 450 ml = 94.5 ml = 0.0945 L
At standard temperature and pressure (STP), using the Ideal Gas Law we can estimate the number of moles:
(1.0 atm) (0.0945 L) = n (0.08205 L·atm/K·mol) (295 K)
After calculating n, the number of moles of oxygen, we can find the mass by multiplying by the molar mass of O₂, which is approximately 32 g/mol. Given that air's molar weight is M = 28.8 g (average based on approximately 80% N₂ and 20% O₂), and considering O₂'s share, the calculation would show that there are approximately 0.6 grams of oxygen per breath.