Calculate the molar mass of the aluminum oxide. A 5.00g strip of aluminum is reacted in air, producing an oxide weighing 9.36g. Calculate the percent oxygen and aluminum in the compound.Calculate the % error for percent of aluminum calculated.
1) Yes, indeed. Al?O? is the correct formula for aluminum oxide. Because the ionic formula is Al?? and O??. (Aluminum has an oxidation number of 3+ ; and oxygen has an oxidation number of 2- . So a neutral ionic compound will have the formula Al?O?. Each element will take the number of the opposite ion.
molar mass.. .. molar mass Al2O3 = 2 x 26.98 + 3 x 16.00 = 101.96 g/mol mass %'s based on formula .. % Al in Al2O3 = (2 x 26.98 / 101.96) x 100% = ___ % .. % O in Al2O3 = (3 x 16.00 / 101.96) x 100% = ___ % mass % based on experimental data .. % Al in oxide = (5.00g / 9.36g) x 100% = ___% .. % O in oxide = ( (9.36g - 5.00g) / 9.36g) x 100% = __ % and finally .. % error = (|measured - accepted| / |accepted|) x 100% = ___% ********* here's the answer for the ALUMINUM calcs .. % Al in Al2O3 = (2 x 26.98 / 101.96) x 100% = 52.92% .. % Al in oxide = (5.00g / 9.36g) x 100% = 53.42% .. % error = ( | 53.42% - 52.92% | / | 52.92% | ) x 100% = 0.95% you get to do the oxygen calcs
