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Stoichiometric Calculations The Big Kahuna

Stoichiometry. Stoichiometric Calculations The Big Kahuna. Stoichiometry. Greek stiocheion – element metron – measure. Proportional Relationships.

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Stoichiometric Calculations The Big Kahuna

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  1. Stoichiometry Stoichiometric CalculationsThe Big Kahuna

  2. Stoichiometry Greek stiocheion – element metron – measure

  3. Proportional Relationships • Stoichiometry is all about proportional relationships. Certain amounts of ingredients are needed to make certain amounts of food or other things. • In our case, the ingredients are the reactants and the food is the products.

  4. A. Proportional Relationships X Ratio of eggs to cookies • I have 5 eggs. How many cookies can I make? 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. 5 eggs 5 doz. 2 eggs = 12.5 dozen cookies

  5. 1 stick + 2 gloves = 1 player 2 sticks: 8 gloves: 5 gloves: needs 4 gloves to make 2 players needs 4 sticks to make 4 players makes 2.5 players

  6. 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

  7. 2 Mg + O2 2 MgO • We can read this in several ways: • For every 1 mole of oxygen used, 2 moles of magnesium oxide are formed. • For every 2 moles of magnesium used, 1 mole of oxygen is required. • Come up with two similar sentences to these ones that are also true.

  8. B. Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Determine conversion factors. • Mole ratio - moles  moles • Molar mass - moles  grams Core step in all stoichiometry problems!! 4. Calculate unknown

  9. C. Stoichiometry Problems Ex 1) How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas? 2KClO3 2KCl + 3O2 ? mol 9 mol 9 mol O2 2 mol KClO3 3 mol O2 = 6 mol KClO3

  10. sm 12.0 g # moles Cu = # moles Cu = mm 63.54 g/mol Ex 2) How many grams of silver will be formed from 12.0 g copper? Cu + 2AgNO3 2Ag + Cu(NO3)2 mass = ? sm = 12.0 g # moles Ag = 0.378 mol mass Ag = (# mol) (mm) mass Ag = (0.378 mol) (107.87 g/mol) mass Ag = 40.77 g # moles Cu = 0.189 mol

  11. sm 75.0 g # moles Al = # moles Al = mm 26.98 g/mol Ex 3) If you dropped 75.0 g of aluminum into sulfuric acid, how many grams of hydrogen gas would be produced? 2Al + 3 H2SO4 Al2(SO4)3 + 3H2 sm = 75.0 g mass = ? # moles H2 = 4.17 mol mass H2 = (# mol) (mm) mass H2 = (4.17 mol)(2.016 g/mol) # moles Al = 2.78 mol mass H2 = 8.41 g

  12. Assignment • Stoichiometry: Mass-Mass problems from the workbook.

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