Question

if 6.75g of oxide of lead was reduced to 6.12g of metal, calculate the empirical formula of the oxide​

Answer 1

Mass lost = weight of oxygen = 6.75 - 6.12 = 0.63 g

0.63 g / 16.0 g/mole = 0.0394 moles O
6.12 g / 207.2 g/mole = 0.0295 moles Pb

Ratio being roughly 3:4, the empirical formula is Pb3O4 (which is one of the mixed oxides of lead).