...oxygen at 2.19 atm and 422k...? Part 1:

Iron pyrite (FeS2) is the form in which much of
the sulfur exists in coal. In the combustion of
coal, oxygen reacts with iron pyrite to produce
iron(III) oxide and sulfur dioxide, which is a
major source of air pollution and a substantial
contributor to acid rain. What mass of Fe2O3
is produced from the reaction is 81 L of oxygen
at 2.19 atm and 422.15K with an excess of iron
pyrite?
Answer in units of g.

Part 2:

If the sulfur dioxide that is generated above
is dissolved to form 3.4 L of aqueous solution, what is the molar concentration of the resulting sulfurous acid (H2SO3) solution?
Answer in units of M.

Part 3:

What mass of SO2 is produced in the burning
of 1 tonne (1 t = 1000 kg) of high-sulfur coal,
if the coal is 5% pyrite by mass?
Answer in units of kg.

Part 4:

From the previous problem, what is the volume of the SO2 gas at 2.1 atm and 295.15oC?
Answer in units of L.

plz help!!! i've tried this using the PV=nRT formula and then using the ratio after balancing the equation but i keep getting it wrong....idk why...help me? plzzz