dalton's atomic theory...?

Question

Consider the following chart:
Compound Mass Iodine(g) Mass Fluorine(g)
(1) 4.75 3.56
(2) 7.64 3.43
(3) 9.41 9.86
When asked to find the mass of fluorine per gram of iodine in each compound, I found (1) 0.7495g F/g I , (2) 0.44895g F/ g I
(3) 1.0478g F / g I.

I am now asked to explain how these numbers support the atomic theory however, I don't see anyway how they do: they do not support the law of multiple proportions or any other part of the theory - AM I MISTAKEN? if so, how does this support the theory??

which ratios? What answer am I supposed to be getting?

Answer 1

OK, now that you have the mass ratios, you need to look at the ratios of the ratios:

#1/#2 = 1.66945 ≈ 5/3
#3/#1 = 1.39800 ≈ 7/5
#3/#2 = 2.33389 ≈ 7/3

Notice that these ratios can all be expressed as ratios of small whole numbers. This supports Dalton's law of multiple proportions.

Answer 2

Dalton?? Anyway I think we are comparing the ratio of masses of I and F in various compounds here, so it looks like an I atom is combined with different numbers of F atoms..eg IFn where n= 1,2,3 etc in its simplest formula.
This is borne out by your data
ratio3/ratio2=1.0478/0.44895= 2.333=7/3
ratio3/ratio1=1.0478/0.7495= 1.400=7/5
ratio1/ratio2=0.7495/0.44895= 1.670=5/3
This shows that for these compounds, the simplest atomic formulae are respectively
1)IF5 2)IF3 and 3)IF7..(we seem to be missing a simple IF somewhere)
This shows that Iodine and Fluorine combine in fixed integer proportions when combined in different compounds, so I guess that would give strong evidence for a particle theory of matter...
(Check this up with your values for the atomic masses of Iodine and Fluorine from your periodic table for confirmation)

Answer 3

A star for looking at it so critically; that is what you are supposed to do but lots don't.

Divide the first two ratios by the third. You will not get spot on simple fractions, because of experimental error, but you will be pretty close.