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Percent Composition of Mixtures and Compounds

Percent Composition of Mixtures and Compounds. What is a Percent?. A part of a whole A fraction x 100 How many parts out of 100. The “Percent Formula”. Percent Composition of Mixtures (by mass).  The “ whole ” will be the mass of the whole entire mixture.

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Percent Composition of Mixtures and Compounds

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  1. Percent Composition of Mixtures and Compounds

  2. What is a Percent? • A part of a whole • A fraction x 100 • How many parts out of 100

  3. The “Percent Formula”

  4. Percent Composition of Mixtures (by mass) The “whole” will be the mass of the whole entire mixture. The “part” will be the mass of the part of the mixture you are interested in.  The “percent” will express the part out of 100 equal parts. All percents must add to 100!

  5. Example: Percent Composition of a Mixture (by mass) Whole = ? 150. g + 220. g + 125 g = 495 g % Pretzels = (150. g / 495 g) * 100 = 30.3% % Peanuts = (220. g / 495 g) * 100 = 44.4% % Cereal = (125. g / 495 g) * 100 = 25.3% Julia makes a Chex Mix with 150. grams of pretzels, 220. grams of peanuts, and 125 grams of cereal. What is the percent composition of her Chex Mix?

  6. Percent Composition of a Compound (by mass) • A compound is a “chemical” mixture since a chemical reaction between elements forms a compound (although the elements cannot be separated physically anymore). Ex: 2Na (s) + Cl2 (g) → 2NaCl (s)

  7. Percent Composition of Compounds (by mass) • The “whole” will be the mass of the whole compound (which you can get from the Law of Conservation of Mass) • The “part” will be the mass of the part of the compound you are interested in (which element) • The “percent” will express the part out of 100 equal parts. All percents must add to 100!

  8. Example: Percent Composition of a Compound (by mass) 63.98 grams of sodium (Na) metal reacts completely with 70.90 grams of chlorine gas (Cl2) to produce pure sodium chloride (table salt). What is the percent composition of table salt (by mass)? Whole = ? 63.98 g + 70.90 g = 134.88 g (by the Law of Conservation of Mass) % Sodium = (63.98 g/ 134.88 g) * 100 = 47.43 % % Chlorine = (70.90 g / 134.88 g) * 100 = 52.57% Ex: 2Na (s) + Cl2 (g) → 2NaCl (s)

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