Question

A resting adult requires about 240 ml of pure oxygen/mind and breathes about 12 times every minute. if inhaled air contains 20 percent oxygen by volume and exhaled air 16 percent, what is the volume of air per breath

Answer 1

12 times breathe give 240 ml of pure $O_{2}$. Each breathe gives 20 ml of $O_{2}$.

Let us consider, volume of air per breathe= x ml.

Pure $O_{2}$ from inhaled air= $\frac{20}{100}x$ ml and Pure $O_{2}$ from exhaled air= $\frac{16}{100}x$ ml.

Pure $O_{2}$ from inhaled and exhaled air= 20 ml

So, $\frac{20}{100}x$ + $\frac{16}{100}x$ = 20

Therefore, x = 55.5 ml

So, volume of air per breath= 55.5 ml.