申論題

4. A 0.611-g sample of an alloy containing Al and Mg is dissolved and treated to prevent interferences by the alloy's other constituents. Aluminum and magnesium are precipitated using 8-hydroxyquinoline, providing a mixed precipitate of Al(C₉H₆NO)₃ and Mg(C₉H₆NO)₂ that weighs 7.815 g. Igniting the precipitate converts it to a mixture of Al₂O₃ and MgO that weighs 1.002 g. Please calculate the %w/w Al and %w/w Mg in the alloy. (Al(C₉H₆NO)₃: MW=459.45 g/mol； Mg(C₉H₆NO)₂: MW=312.61 g/mol； Al: MW= 26.982 g/mol； Mg: MW= 24.305 g/mol； Al₂O₃: MW=101.96 g/mol； MgO: MW: 40.3044 g/mol)