Gallium metal of mass 29.0 g reacts as 4Ga + 3O2 giving 2Ga2O3. What mass of Ga2O3 can be prepared?

1. Mass problems need three steps: convert mass to moles, apply the factor, convert back to mass. 2. Convert 29.0 g of gallium to moles using the molar mass of gallium. 3. Apply the stoichiometric factor, which is 2 mol Ga2O3 per 4 mol Ga. 4. Convert that molar amount of Ga2O3 to a mass using its molar mass. 5. Carrying the full chain through gives 39.0 g of Ga2O3. 6. The product mass exceeds the metal mass because oxygen has been added to the gallium. 7. Answering 58.0 g ignores that only 2 mol of oxide form per 4 mol of gallium. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.3 Reaction Stoichiometry_