Question

The mineral hausmannite is a compound of manganese-55 and oxygen-16. If 72% of the mass of hausmannite is due to manganese, what is the empirical formula of Hausmannite? Can you show work?

Answer 1

Let mass of hausmannite = 100 g

mass manganese = (mass of hausmannite) * (fraction of manganese)

mass manganese = (100 g) * (72 %)

mass manganese = (100 g) * (72 / 100)

mass manganese = (100 g) * (0.72)

mass manganese = 72 g

mass oxygen = (Total mass) - (mass manganese)

mass oxygen = (100 g) - (72 g)

mass oxygen = 28 g

moles manganese = (mass manganese) / (molar mass manganese)

moles manganese = (72 g) / (55.938 g/mol)

moles manganese = 1.287 mol

moles oxygen = (mass oxygen) / (molar mass oxygen)

moles oxygen = (28 g) / (15.999 g/mol)

moles oxygen = 1.750 mol

moles oxygen / moles manganese = (1.750 mol) / (1.287 mol)

moles oxygen / moles manganese = 1.35

empirical formula : MnO_1.35

empirical formula : Mn₃O₄