When adding a sample of X to excess water,25.4dm3 of methane was collected and a precipitate of Al(OH)3 formed.when the precipitate was heated to constant mass 71.4g of aluminium oxide was obtained
Determine the empirical formula of compound X
Compound X is found to contain aluminium and carbon only.?
2015-05-09 8:09 am
回答 (1)
2015-05-09 8:47 pm
Supposing all the carbon in compound X was converted to methane, and supposing the methane was measured at STP:
(25.4 dm^3 CH4) / (22.414 dm^3/mol) x (1 mol C / 1 mol CH4) = 1.1332 mol C
Supposing all the Al in Compound X was converted to Al2O3:
(71.4 g Al2O3) / (101.96128 g Al2O3/mol) x (2 mol Al / 1 mol Al2O3) = 1.4005 mol Al
Divide by the smaller number of moles:
(1.4005 mol Al) / 1.1332 mol = 1.2359
(1.1332 mol C) / 1.1332 mol = 1.0000
In order to achieve integer coefficients, multiply by 4, then round to the nearest whole numbers to find the empirical formula:
Al5C4
[This is not the actual formula for aluminum carbide, but it is what the given data seem to say. Perhaps the methane was not measured at STP, but without any other information about T and P, that's what you must assume.]
(25.4 dm^3 CH4) / (22.414 dm^3/mol) x (1 mol C / 1 mol CH4) = 1.1332 mol C
Supposing all the Al in Compound X was converted to Al2O3:
(71.4 g Al2O3) / (101.96128 g Al2O3/mol) x (2 mol Al / 1 mol Al2O3) = 1.4005 mol Al
Divide by the smaller number of moles:
(1.4005 mol Al) / 1.1332 mol = 1.2359
(1.1332 mol C) / 1.1332 mol = 1.0000
In order to achieve integer coefficients, multiply by 4, then round to the nearest whole numbers to find the empirical formula:
Al5C4
[This is not the actual formula for aluminum carbide, but it is what the given data seem to say. Perhaps the methane was not measured at STP, but without any other information about T and P, that's what you must assume.]
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