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Combustion Reactions

Combustion Reactions. What are combustion reactions?. A combustion reaction occurs when a compound that contains carbon and hydrogen is burned in Oxygen gas (O 2 ). It always produces carbon dioxide and water vapor. Example: CH 4 + 2 O 2  CO 2 + 2 H 2 O

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Combustion Reactions

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  1. Combustion Reactions

  2. What are combustion reactions? • A combustion reaction occurs when a compound that contains carbon and hydrogen is burned in Oxygen gas (O2). It always produces carbon dioxide and water vapor. • Example: • CH4 + 2 O2 CO2 + 2 H2O • Many times the compound also contains oxygen • Example: • 2C3H4O3 +5 O2 6CO2 + 4 H2O • Notice the products remain the same.

  3. Using a combustion reaction to find empirical formula. • Vitamin C is a compound made up of carbon, hydrogen and oxygen atoms. When we combust 1.00g of vitamin C we produce 1.50g of carbon dioxide and 0.408g of water vapor. Find the empirical formula of vitamin C. • #1 We know that it is a combustion reaction so: • CxHyOz + O2 CO2 + H2O • #2 We notice that all the carbon atoms from vitamin C became part of carbon dioxide so; • 1.50g CO2 x 1 mole CO2/ 44 g = 0.0341 moles of CO2 • Since there is only 1 atom of carbon in CO2 we have 0.0341 moles of C

  4. #3 We have 0.408 g of H2O so all the hydrogen atoms from vitamin C became part of the water vapor. • 0.408 g H2O x 1 mole H2O / 18 grams = 0.0227 moles of H2O • Notice thee are TWO atoms of hydrogen in H2O so; • We have 2x 0.0227= 0.0454 moles of Hydrogen • #4 We now go back to Vitamin C, CxHyOz • We know we have: • 0.0341 moles of C x 12g/1 mole of C= .409g of C • 0.0454 moles of H x 1g / 1mole of H = .0454g of H • Oxygen = (1.00- .409- .0454)= .546 g of O

  5. #5 We now know the grams of each of the elements that make up vitamin C • C = .409g x 1mole C/ 12g = .0341 moles • H = .0454 g x 1mole H/ 1g = .0454 moles • O = .546 g x 1mole O/ 16 g = .0341 moles • Divide all moles by smallest answer • C= .0341/.0341 =1 • H= .0454/.0341 = 1.33 • O = .0341/ .0341= 1 • Multiply all answers by 3 and we get • C3 H4 O3

  6. Homework • 1.Balance the following reactions • A) CaO + HNO3 Ca(NO3)2 + H2O • B) NH3 + H2SO4  (NH4)2SO4 2.Given the following reaction, find the grams of H2O are produced • 2C6H6+ 15 O2 12 CO2 + 6 H2O • You start with 125 grams of C6H6 and 875 g of O2 3. Find the empirical formula of a compound that is made up of C,H and O. When you combust 2.00g of the compound in excess oxygen gas you produced 3.83g of CO2 and 2.35g of H2O

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