Answer to Question #235750 in Physics for Totoy

Question

The density of air under standard laboratory conditions is 1.29 kg/m3, and about 20% of that air consists of oxygen. Typically, people breathe about of 1/2L of air per breath. (a)How many grams of oxygen does a person breathe in a day? (b) If this air is stored uncompressed in a cubical tank, how long is each side of the tank?

Answer 1

(a) Find the mass of air people breath:

$$m=\rho V=1.29·0.5·10^{-3}=6.45·10^{-4}\text{ kg}.$$

This is equivalent to 0.645 g. The mass of oxygen is 20%:

$$m_{\text{O}_2}=m\omega=0.645·0.2=0.129\text{ g}.$$

(b) Assuming we consider cubical portion of space:

$$a=\sqrt[3]{V}=\sqrt[3]{500}=7.9\text{ cm}.$$