Analysis of a compound known to contain only Mg, P and O gives this analysis.
21.8%Mg, 27.7% P and 50.3% O. What is its empirical formula?
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Molar mass in g/mol
Mg = 24
P = 31
O = 16
Let us say we have 100g of the compound. Then we have 21.8 g of Mg, 27.7g of P and 50.3g of O.
Amount of Mg moles `= 21.8/24 = 0.91`
Amount of P moles `= 27.7/31 = 0.894`
Amount of O moles `= 50.3/16 = 3.144`
`Mg : P : O `
`= 0.91 : 0.89 : 3.144 `
`= 0.91/0.89 : 0.89/0.89 : 3.144/0.89 `
`= 1 : 1 : 3.5`
`= 2 : 2 : 7`
So the emperical formulae is `Mg_2P_2O_7` . The correct answer is C.
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