When mercuric oxide decompose, 18.522 g Mercury and 1.478 g of oxygen forms. How much mercuric oxide is used in the experiment?

Elemental phosphorus bums in oxygen with an intensely hot flame, producing a brilliant light and clouds of the oxide product. These properties of the combustion of phosphorus have led to its being used in bombs and incendiary devices for warfare. :math>P4(s)+5O2(g)2P2O5(s) 4.95 g of phosphorus is burned, what mass of oxygen does it combine with?

Atomic masses are relative masses. What does this mean?

An adult human body contains 6.0 L blood, which contains about 15.5 g hemoglobin per 100.0 mL blood. The molar mass of hemoglobin is approximately 64,500 g/mol and there is 4 mol iron per 1 mol hemoglobin. A news item claims that there is sufficient iron in the hemoglobin of the body that this iron, if it were in the form of metallic iron, could make a 3-in. iron nail that weighs approximately 3.7 g. Show sufficient calculations to either support or refute the claim.