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Laws of Definite Proportions & Multiple Proportions. PreAP Chemistry. Law of Definite Proportion. Put forth by Joesph Louis Proust (1754-1816) in 1800
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Laws of Definite Proportions & Multiple Proportions PreAP Chemistry
Law of Definite Proportion • Put forth by Joesph Louis Proust (1754-1816) in 1800 • States that different samples of the same compound always contain its constituent elements in the same proportion by mass regardless of the source. • It is an intensive property. • Example CO and CO2 • CO = O/C = 1/1 • CO2 = O/C =2/1 • CO to CO2 = 1:2
Calculation • Mass Fraction = Mass of element Mass of Compound • Mass Percent = Mass of element x 100 Mass of Compound • Mass of element in a sample = Mass of compound x Mass of element in a sample Mass of Compound
Law of Multiple Proportions • Derived by John Dalton (1766-1844) in between 1803-1807. • States if two elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in a ratio of small whole numbers. • It is an intensive property. • Example – H2O and H2O2
Difference between Laws of multiple proportions and definite proportions • Both laws have to do with relating to Dalton's Atomic Theory. The only difference is that the Law of Definite Proportions deals with elements combining to form ONE compound in a simple whole number ratio. The • Law of Multiple Proportions is comparing the same 2 elements that make up 2 different compounds, the division of these 2 ratios should equal a simple whole number ratio. • For example: Carbon and oxygen can combine to form carbon monoxide and carbon dioxide. If you calculated each compounds ration of oxygen to carbon you would get the following ratios: compound A would equal a combining ratio of 1.34:1 (O:C). Compound B would equal a combining ratio of 2.67:1 (O:C). • If you divided the bigger ratio by the smaller ratio you would have that oxygen combines with a ratio of 2.67/1.34 which would equal 1.99:1, which is close enough to 2:1.