Presentation on theme: "What Proust and Dalton contributed to Modern Atomic Theory."— Presentation transcript:
What Proust and Dalton contributed to Modern Atomic Theory
Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass.
If there is one H 2 O molecule
Or many H 2 O molecules
The proportion by mass will always be the same! Percent by mass (%) = mass of element x 100 mass of compound
Magnesium combines with oxygen to form magnesium oxide. If g of magnesium reacts completely with 6.96 g of oxygen, what is the percent by mass of oxygen in magnesium oxide?
The entire sample of magnesium oxide is: g magnesium g oxygen = g magnesium oxide The percent of magnesium in magnesium oxide is: g magnesium_____ X 100 = 60% g magnesium oxide The percent of oxygen in magnesium oxide is: 6.96 g oxygen_______ X 100 = 40% g magnesium oxide
Your answer should equal 100% of the sample: 60% + 40%= 100%