1) If the volumes hypothesis is correct, then the relative masses of gas molecules can be computed from gas densities. (After all, the density is the mass of a unit volume, and that volume contains the same number of molecules, whatever the gas.) Construct a table of relative molecular masses based on the gas densities reported by Avogadro and using hydrogen as the unit molecular mass.
(Hint: The molecular mass of "nitrous gas" relative to hydrogen is the ratio of the mass of a "nitrous gas" molecule to a hydrogen molecule.)
molecule gas density (air = 1) oxygen 1.10359 hydrogen 0.07321 nitrogen 0.96913 oxymuriatic acid 2.470 water vapor 0.625 nitrous gas 1.03636 nitrous oxide 1.52092 muriatic acid gas 1.278
2) The mass scale computed in the previous exercise has the hydrogen molecule as its unit mass. It might make more sense to take the hydrogen atom as the unit. What is the mass of the hydrogen molecule if the hydrogen atom is one mass unit? On this sacle, what is the mass of the oxygen molecule, nitrous gas, etc.?
3) Hydrogen, oxygen, nitrogen, and "oxymuriatic acid" are all diatomic elements. (Nowadays we call "oxymuriatic acid" chlorine.) On this scale where a hydrogen atom is one mass unit, what are the atomic masses of these elements?
4) Assume that molecules are made of small whole numbers of atoms. The masses of all of the constituent atoms ought to add up to the mass of a molecule.
a) Water vapor is a compound of hydrogen and oxygen. How many atoms of each element in one molecule of water vapor? Show that the molecular mass of water vapor is consistent with the atomic masses of the atoms and your proposed formula. (For example, Dalton thought that the formula for water was HO. If that were correct, then the molecular mass of water vapor ought to equal the atomic mass of hydrogen plus that of oxygen.)
b) Nitrous gas is a compound of nitrogen and oxygen. How many atoms of each element in one molecule of nitrous gas? Show that the molecular mass is consistent with the formula.
c) Nitrous oxide is another compound of nitrogen and oxygen. How many atoms of each element in one molecule of nitrous oxide? Show that the molecular mass is consistent with the formula.
d) Muriatic acid gas is a compound of hydrogen and oxymuriatic acid. How many atoms of each element in one molecule of muriatic acid gas? Show that the molecular mass is consistent with the formula.
5) Write balanced chemical equations for the formation of water vapor, nitrous gas, nitrous oxide, and muriatic acid from their diatomic elements.
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