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Chapter 8

Chapter 8. Percent Composition. Water is made of hydrogen and oxygen. How many grams of each are in the sample of water below?. % =. Mass of element. Percent Composition. Percent composition is the percent by mass of an element within a compound.

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Chapter 8

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  1. Chapter 8 Percent Composition

  2. Water is made of hydrogen and oxygen. How many grams of each are in the sample of water below?

  3. % = Mass of element Percent Composition Percent composition is the percent by mass of an element within a compound. • Divide the mass of each element by the formula mass of the compound X 100 Formula Mass of compound

  4. Percent Composition of H2O 2 X H = 2 X 1.0 g = 2.0 g 1 X O = 1 X 16.0 g = 16.0 g gram formula mass = 2.0 g + 16.0 g = 18.0 g % H = 2.0g X 100 = 11.2% 18.0g % O = 16.0g X 100 = 88.8% 18.0g

  5. Percent Composition of H2O 2 X H = 2 X 1.0 g = 2.0 g 1 X O = 1 X 16.0 g = 16.0 g gram formula mass = 2.0 g + 16.0 g = 18.0 g % H = 2.0g X 100 = 11.2% 18.0g % O = 16.0g X 100 = 88.8% 18.0g What does this mean?

  6. Pure water’s mass is 11.2% hydrogen and 88.8% oxygen. (0.112)(128.98g) = 14.45g H (.888)(128.98g) = 114.53g O or 128.98g – 14.45g = 114.53g O 11.2% H 88.8% O

  7. Percentage Composition • Remember that you have to calculatetheformula mass! The problem doesn't say to do so...

  8. Determine the Percent Composition of C6H12O6

  9. Determine the Percent Composition of C6H12O6 6 X C = 6 X 12.0 g = 72.0g 12 X H = 12 X 1.0g = 12.0g 6 X O = 6 X 16.0g = 96.0g gfm = 180.0 grams/mole

  10. Determine the Percent Composition of C6H12O6 6 X C = 6 X 12.0 g = 72.0g 12 X H = 12 X 1.0g = 12.0g 6 X O = 6 X 16.0g = 96.0g gfm = 180.0 grams/mole % C = % H = % O = (72.0g/180.0g) X 100 =40.0% (12.0g/180.0g) X 100 =6.67% (96.0g/180.0g) X 100 =53.3%

  11. How many grams of carbon are in 156g C6H12O6 6 (156g)(0.400) = 62.4g carbon 12 6 Molar % C = % H = % O = (72.0g/180.0g) X 100 =40.0% (12.0g/180.0g) X 100 =6.67% (96.0g/180.0g) X 100 =53.3%

  12. What is this? a

  13. Iron Pyrite “Fool’s Gold” (FeS2) a

  14. How many grams of sulfur are in this 28.8g sample of iron pyrite FeS2? a

  15. How many grams of sulfur are in this 28.8g sample of iron pyrite FeS2? 15.4g S a

  16. How many grams of sulfur are in this 28.8g sample of iron pyrite FeS2? 15.4g S Fe + 2(S) 55.8 + 2( 32.1) = 120 g/mol %S = 64.2/120 x 100= 53.5%S 28.8g x 0.535 = 15.4g S a

  17. Homework • Percentage Composition Worksheet (Due in 2 Days).

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