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The Law of Definite Proportions. What Proust and Dalton contributed to Modern Atomic Theory . The Law of Definite Proportion’s Definition. Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass . The Law of Definite Proportions.
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The Law of Definite Proportions What Proust and Dalton contributed to Modern Atomic Theory
The Law of Definite Proportion’s Definition Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass.
The Law of Definite Proportions If there is one H2O molecule
The Law of Definite Proportions Or many H2O molecules
Percent by Mass The proportion by mass will always be the same! Percent by mass (%) = mass of element x 100 mass of compound
The Law of Definite Proportions Calculations Magnesium combines with oxygen to form magnesium oxide. If 10.57 g of magnesium reacts completely with 6.96 g of oxygen, what is the percent by mass of oxygen in magnesium oxide?
Calculations The entire sample of magnesium oxide is: 10.57 g magnesium + 6.96 g oxygen = 17.53 g magnesium oxide The percent of magnesium in magnesium oxide is: 10.57 g magnesium_____ X 100 = 60% 17.53 g magnesium oxide The percent of oxygen in magnesium oxide is: 6.96 g oxygen_______ X 100 = 40% 17.53 g magnesium oxide
Checking Your Answer Your answer should equal 100% of the sample: 60% + 40%= 100%