Help with this chemistry question!

Question

consider 100.0-g samples of two different compounds consisting only of carbon and oxygen. one compound contains 27.2g of carbon and the other has 42.9 g of carbon. how can these data support the law of multiple proportions if 42.9 is not a multiple of 27.2? show that these data support the law of multiple proportions.

Answer 1

lets calculate the empirical formula of both compounds , to see if they have whole number ratios

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first compound

27.2 grams Carbon @ 12 g/mole = 2.27 moles carbon

72.8 grams oxygen @ 16 grams/mole = 4.55 moles oxygen

2.27 moles carbon -:- 2.27 = 1 part Carbon

4.55 moles oxygen -:- 2.27 = 2 parts Oxygen

empirical formula: CO2

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second compound

42.9 grams carbon @ 12 g/mole = 3.58 moles carbon

57.1 grams oxygen @ 16 grams /mole = 3.57 moles oxygen

empirical formula : CO

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law of multiple proportions:

"f two elements form more than one compound between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.

Another way to say this is:

A law proposed by Dalton which states that when elements combine, they do so in the ratio of small whole numbers. For example carbon and oxygen react to form CO or CO2, but not CO1.8."

http://en.wikipedia.org/wiki/Law_of_mult...

so this is the "text book" example proof for the law of multiple proportions, that's your answer: they are whole # ratio compounds