Fe2(SO4)3 (s) -> Fe2O3 (s) + 3SO3 (g) What volume of sulfur trioxide at r.t.p will be produced, when 25g of iron sulfate are heated.

Answer 1

Note: there is no nationally recognized unit of r.t.p., so I'll use what is recognized and referred to as NTP or normal temperature and pressure (20ºC = 293K and 1 atm).

Fe2(SO4)3(s) ==> Fe2O3(s) + 3SO3(g) ... balanced equation

Using dimensional analysis, the stoichiometry of the balanced equation and the ideal gas law, we proceed as follows:

25 g Fe2(SO4)3 x 1 mol Fe2(SO4)3 / 400 g x 3 mol SO3 / mol Fe2(SO4)3 = 0.1875 moles SO3

PV = nRT and solving for volume (V), we have...

V = nRT/P = (0.1875 mol)(0.0821 Latm/Kmol))(293)/1 atm

V = 4.5 liters

UPDATE:

If you haven't learned the ideal gas law of PV = nRT but you have learned that at r.t.p. or NTP that 1 mole of any gas = 24 liters, then you just find the moles as above, 0.1875 moles SO3, and multiply that by 24 liters/mol.

0.1875 moles x 24 liters/mole = 4.5 liters.