toxin - 12-8-2005 at 14:27
Sulfur forms two compounds with fluorine. In one of them it is observed that 0.447 g of sulfur is combined with 1.06 g of fluorine while in the other,
0.438 g of sulfur is combined with 1.56 g of fluorine.
How would I show that these data illustrate the law of multiple proportions ?
would (0.447/1.06)/(0.438/1.56) work, why or why not ?
Magpie - 12-8-2005 at 17:22
Your fraction = 1.502 which is very nearly equal to 3/2. If I remember the law right it says atoms combine in ratios of whole numbers. Your fraction
does show this.
Looking at the moles:
compound 1)
moles S = 0.447g/32.064 = 0.0139
moles F = 1.06/19.00 = 0.056
atomic ratio F/S = 0.056/0.0139 = 4.01 = very nearly 4/1.
compound 2)
moles S = 0.438/32.064 = 0.0137
moles F = 1.56/19.00 = 0.0821
atomic ratio F/S = 0.0821/0.0137 = 5.99 = very nearly 6/1.
The ratio of these ratios is 6/4 = 3/2 which is, of course, the same as your original fraction.
So I think your fraction does show this law. Converting to moles just shows the atomic ratio for each compound.
Does this make any sense? 
[Edited on 13-8-2005 by Magpie]
2nd Edit:
When I got off my ass and actually looked up the Law of Multiple Proportions it says that when 2 elements combine in more than one compound the ratio
of the weights of one element to a fixed weight of the other will be that of small whole numbers. So I think your original fraction shows this to be
true. Just presenting the complex fraction as the answer may be a little obsure to the teacher, however. 
[Edited on 13-8-2005 by Magpie]
[Edited on 13-8-2005 by Magpie]
Magpie - 13-8-2005 at 14:54
Toxin,
I answered "yes" to your question but did not explain "why," at least not very directly.
Working directly with the Law:
Compound 1): weight ratio of S/F = 0.447g/1.06g
Compound 2): weight ratio of S/F =
0.438g/1.56g
Weight of S in compound 2 for 1.06 g F =
(1.06)[0.438g/1.56g]
Ratio of weights of S (cmpd 1/cmpd 2) to same amount of F =
0.447g/{1.06g[0.438g/1.56g]}
Rearranging this = (0.447g/ 1.06g)/(0.438/1.56), which is what you have. And in agreement with the law this is equal to 3/2, a ratio of 2 small
numbers.
toxin - 13-8-2005 at 19:04
Magpie, what do you mean by weight here, aren't weight and mass two different things ?
"
Compound 1): weight ratio of S/F = 0.447g/1.06g
Compound 2): weight ratio of S/F =
0.438g/1.56g
Weight of S in compound 2 for 1.06 g F =
(1.06)[0.438g/1.56g]
Ratio of weights of S (cmpd 1/cmpd 2) to same amount of F =
0.447g/{1.06g[0.438g/1.56g]}
"
12AX7 - 13-8-2005 at 21:32
Weight is mass on Earth. 
Tim
toxin - 14-8-2005 at 08:27
Isn't the gram a measure of mass ?
unionised - 14-8-2005 at 12:23
Strictly the weight is the gravitational attraction of the earth and is measured in Newtons. Mass is the amount of stuff and is measured in grams or
kilograms.
The distinction is totally irrelevant here. On the moon tha weights would be different, but the ratios would still be the same.