The complete balanced chemical reaction to this would be:
<span>2 Fe + 3/8 S8
--> Fe2S3</span>
First convert mass into number of moles.
moles Fe = 3 g / (55.845 g/mol) = 0.05372 mol Fe
moles S8 = 2.5 g / (256.52 g/mol) = 0.0097458 mol S8
Then we find the limiting reactant. The limiting reactant
is the one which has lower (moles/coefficient) ratio.
Fe = 0.05372 / 2 = 0.02686
S8 = 0.0097458 / (3/8) = 0.02599
So since S8 has lower ratio, therefore it is the limiting
reactant so we base our calculation from it. From the reaction, we get 1 mole
of Fe2S3 for every 3/8 mol of S8, therefore:
moles Fe2S3 = 0.0097458 mol S8 * (1 mole Fe2S3 / 3/8 mol
S8)
moles Fe2S3 = 0.02599 mol
The molar mass of Fe2S3 is 207.9 g/mol, so the mass is:
mass Fe2S3 = 0.02599 mol * 207.9 g/mol
<span>mass Fe2S3 = 5.4 grams</span>
