When .422g of phosphorus is burned, .967g of white oxide isobtained. Determine t
ID: 686758 • Letter: W
Question
When .422g of phosphorus is burned, .967g of white oxide isobtained.Determine the empirical formula of the oxide and write a balancedequation for the reaction of phosphorus and molecular oxygen on thebasis of this empirical formula.
Please help me. I am confused. Will rate lifesaver! When .422g of phosphorus is burned, .967g of white oxide isobtained.
Determine the empirical formula of the oxide and write a balancedequation for the reaction of phosphorus and molecular oxygen on thebasis of this empirical formula.
Please help me. I am confused. Will rate lifesaver!
Explanation / Answer
Okay first of all, the empirical formula is going to be of the formPOn where n is the number of Oxygens per Phosphorusatom. Secondly the balanced equation is going to look something likethis: mP + (n/2)O2 ---> PmOn (there is also heat evolved) Okay so we have the weight of the Phosphorus that we initially has(meaning we have the moles) and we also have the weight of theoxide after all the phosphorus has been burnt. Now the excessweight in the oxide is going to be made up of oxygen atoms. Let'sfind the number of molves of P we had orginally first. n = m / RAM Where n is the number of moles Where m is the mass (in grams) Where RAM is the relative atomic mass (in this case ofphosphorus) n = m / RAM = 0.422 / 30.97 = 0.013626 So the number of moles of P we have is 0.013626 Now let's find the number of moles of oxygen Firstly the mass of oxgen we have is the mass of the oxide minusthe original mass of phosphorus m = 0.967 - 0.422 = 0.545 g n = m / RAM = 0.545 / 16 = 0.03406 So now we know the number of moles of P we have on the right handside of the equation as well as the number of moles of O So we can find the ratio of P : O and that will give us the valueof n and the empirical formula P : O = 0.013626 : 0.03406 ˜ 1 : 2.5 = 2 : 5 So for every two phosphorus atoms we have 5 oxygen atoms andtherefore the empircal formula of the oxide is: P2O5 And from this we can get the balanced equation 4P + 5O2 ---> 2P2O5 I hope this made sense and if it doesn't then please ask!
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