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“Sounds cool….”

STOICHIOMETRY. “Sounds cool….”. Consider: 4NH 3 + 5O 2  6H 2 O + 4NO. Stoichiometry. What do the coefficients tell us? 4 molecules of ammonia react with 5 molecules of oxygen to produce 6 molecules of water and 4 molecules of nitrogen monoxide

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“Sounds cool….”

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  1. STOICHIOMETRY “Sounds cool….”

  2. Consider: 4NH3 + 5O2 6H2O + 4NO Stoichiometry • What do the coefficients tell us? • 4 molecules of ammonia react with 5 molecules of oxygen to produce 6 molecules of water and 4 molecules of nitrogen monoxide • 4 moles of NH3 react with 5 moles of O2 to produce 6 moles of H2O and 4 moles of NO • The “ratio” of NH3 to O2 is 4:5

  3. Ratio of eggs to cookies Proportional Relationships 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. I have 5 eggs. How many cookies can I make? 2 eggs 5 doz. 5 eggs X doz. = X = 12.5 dozen cookies 150 cookies Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  4. Visualizing a Chemical Reaction 2 2 Na + Cl2 NaCl 10 5 10 10 ? 10 5 ___ mole Na ___ mole Cl2 ___ mole NaCl

  5. Proportional Relationships • Stoichiometry • mass relationships between substances in a chemical reaction • based on the mole ratio • Mole Ratio • indicated by coefficients in a balanced equation 2 Mg + O2 2 MgO Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  6. 1 mol = molar mass 1 mole = 22.4 L @ STP 1 mol = 6.02 x 1023 particles Welcome to Mole Island

  7. Stoichiometry Island Diagram Known Unknown Substance A Substance B M Mass Mass Mountain Mass Mole Island Volume Mole Mole Volume V Liter Lagoon Particles Particles P Particle Place Stoichiometry Island Diagram

  8. Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Convert the known substance to moles. • Using the mole ratios of the known and unknown substance, obtain the # of moles for the unknown. 5. Convert the # of moles of the unknown into value requested (mass. Volume…etc.) • Mole ratio - moles  moles Core step in all stoichiometry problems!! 6. Check answer. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  9. 2KClO3 2KCl + 3O2 Example 1: How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas? ? mol 9 mol x mol KClO3 9 mol O2 2 mol KClO3 3 mol O2 = 6 mol KClO3 = Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  10. x mol NO 6 mol H2O x mol H2O 4 mol NO 0.2112 mol H2O x = = 11.33 mol NO x= 17 mol H2O 0.176 mol O2 5 mol O2 6 mol H2O Example 2: Consider : 4NH3 + 5O2 6H2O + 4NO • How many moles of H2O are produced if 0.176 mol of O2 are used? • How many moles of NO are produced in the reaction if 17 mol of H2O are also produced? = Notice that a correctly balanced equation is essential to get the right answer

  11. Cu + 2 AgNO3 2 Ag + Cu(NO3)2 Example 3: How many grams of silver will be formed from 12.0 g copper? 12.0 g ? g n Cu = 12.0 g = 0.189 mol Cu 63.55 g/mol 2 mol Ag 1 mol Cu x mol Ag 0.189 mol Cu x = 0.378 mol Ag = m Ag = 0.378 mol x 107.97 g/mol = 40.8 g Ag Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  12. Example 4 2 TiO2 + 4 Cl2 + 3 C CO2 + 2 CO + 2 TiCl4 x molecules 115 g How many molecules of TiCl4 will be produced by 115.0g TiO2? 3. Convert # of moles of TiCl4 to number of molecules • Convert mass to moles 115.0 g 79.88 g/mol n TiO2 = = 1.440 mol N = n NA = (1.440 mol) (6.022 x 1023molecules/mol) 2. Use mole ratio to obtain # of moles of TiCl4 = 8.672 x 1023 molecules of TiCl4 Therefore, 8.672 x 1023 molecules of TiCl4 will be produced from 115.0 g of TiO2. 2 mol TiO2 2 mol TiCl4 1.440 mol TiO2 x mol TiCl4 = x = 1.440 mol TiCl4

  13. Homework • Read 7.1 • Pg 320 # 1-7 • Read 7.2 • Pg 325 # 1, 2, 5-10

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