a form of phosphorus called red phosphorus is used to match heads. when 0.062g of red phosphorus burns, 0.142g of phosphorus oxide is formed. What is the empirical formula of this oxide?
2006-10-31 09:52:48 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
So 0.142 g phosphorus oxide contains 0.062g P and (0.142 -0.062)g O = 0.08g O
Atomic weight of P ≈ 31 and O ≈ 16
Now 0.062g P = 0.062/ 31mol P and 0.08g O = 0.08/ 16mol O
So atoms of P : atoms of O = 0.002 : 0.005 = 2 : 5
Thus empirical formula is P2O5
2006-10-31 10:05:31 · answer #1 · answered by Wal C 6 · 0⤊ 0⤋
This takes the percent composition and suggests the ratio of atoms present.
Example: A compound composed of oxygen and phosphorus is 56.3% oxygen by mass. Find its empirical formula.
Solution: If 56.3% is oxygen, the rest, 43.7% is phosphorus. I set up a table, thus:
P
O
Elements present.
43.7
31
56.3
16
Ratio of relative presence by mass.
Divide both sides by respective relative atomic masses to get…
1.4
1.4
3.5
1.4
…ratio of relative number of atoms present
Divide both sides by the least amount (1.4 here) to get…
1
2.5
…easier values to inspect. This suggests whole number ratio of…
2
5
…or P2O5 for the empirical formula.
RECALL that you expect to get low, whole numbers out at the end (2 and 5 in the table above). Any small fractions may be attributed to errors in measurement; round accordingly. Any fractions which are close to halves, thirds, quarters, etc. should probably be multiplied out to give whole numbers, none of which need to be 1. Other fractions may well indicate calculation errors on your part.
A compound contains 40.0% carbon and 53.3% oxygen by mass, the balance being hydrogen. Find its empirical formula.
Related Topics: Percent Composition, Molecular Formula
2006-10-31 09:59:01 · answer #2 · answered by Brite Tiger 6 · 0⤊ 0⤋
The molar mass of phosphorus is 31 g, and the atomic mass of oxygen is 16 g. .062 g is .062 / 31 = .002 moles. The mass of oxygen in the phosphorus oxide is .142 - .062 = .08 g, which is .08 / 16 = .005 moles. So there are 5 moles of oxygen to 2 moles of phosphorus, meaning that the empirical formula is P2O5.
2006-10-31 09:56:39 · answer #3 · answered by DavidK93 7 · 1⤊ 0⤋
Hi, just wanted to say, I liked this discussion. very valuable answers
2016-08-23 09:52:03 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Not really sure
2016-08-08 18:26:03 · answer #5 · answered by ? 4 · 0⤊ 0⤋