Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which contains both of those minerals) and is the main component of pearls and the shells of marine organisms, snails, and eggs.
An ordinary breath for a 70-kg adult is about 500ml of air. We call this the tidal volume. Since oxygen is 21% by volume of air, then the volume of oxygen inhaled is about 105ml. The density of pure oxygen at sea level is 1.43kg per cubic metre.
How many molecules of oxygen do breathe in in one breath? The average pair of human lungs can hold about 6 liters of air, but during normal respiration, only about 500 mL (one half of a liter) is inspired. Oxygen makes up 21% of air. There are 2.7 x 1019 (2,751.3) molecules in every cubic centimeter of air. 0.5 liter (500 cubic centimeter) contains 1,375,650 molecules, 21% of which are 288,886.5 oxygen molecules. (see Composition of Air)