# stoichiometry chemistry i: chapter 12 chemistry ih: chapter 12

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- Stoichiometry Chemistry I: Chapter 12 Chemistry IH: Chapter 12
- Slide 3 Options>Print>UNch eck "Background Printing")! SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNch eck "Background Printing")!">
- SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNch eck "Background Printing")! SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNch eck "Background Printing")!
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- Stoichiometry The method of measuring amounts of substances and relating them to each other.
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- Mole A unit of measurement that is equal to 6.02 x 10 23 Also known as Avogadros constant (number) It is the number of atoms of an element in the atomic mass (in grams) of that element.
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- Molar Mass The molar mass (MM) of an element is how much a mole of atoms of that element weighs. Equal to the atomic mass in grams. Ex: whats the molar mass of Be Ex: What is the molar mass of O2?
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- Cont The molar mass (MM) of a compound is how much a mole of formula units of that element weighs. Equal to the molecular mass in grams. Reminder: A formula unit is the smallest ratio of atoms in a unit of a compound. It is designated by its formula. Ex: NaCl, H 2 O Ex: what is the molar mass of NaCl? Ex: What is the molar mass of H 2 O?
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- Practice Calculate the Molar Mass of calcium phosphate Calculate the Molar Mass of calcium phosphate Formula = Formula = Masses elements: Masses elements: Molar Mass = Molar Mass = Ca 3 (PO 4 ) 2
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- Conversions We use conversions all the time! We use conversions all the time! Ex: What is another fraction we can use to express ? Ex: What is another fraction we can use to express ? To convert, we multiply times a conversion factor, which is equal to 1. To convert, we multiply times a conversion factor, which is equal to 1. x 5/5 = 5/10 x 5/5 = 5/10 = 2/4 = 3/6 = 5/10
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- Flowchart Atoms or Molecules Moles Mass (grams) Divide by 6.02 X 10 23 Multiply by 6.02 X 10 23 Multiply by atomic/molar mass from periodic table Divide by atomic/molar mass from periodic table
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- molar mass Avogadros number Grams Moles particles molar mass Avogadros number Grams Moles particles Everything must go through Moles!!! Calculations
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- Chocolate Chip Cookies!! 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen How many eggs are needed to make 3 dozen cookies? How much butter is needed for the amount of chocolate chips used? How many eggs would we need to make 9 dozen cookies? How much brown sugar would I need if I had 1 cups white sugar?
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- Cookies and ChemistryHuh!?!? Just like chocolate chip cookies have recipes, chemists have recipes as well Just like chocolate chip cookies have recipes, chemists have recipes as well Instead of calling them recipes, we call them reaction equations Instead of calling them recipes, we call them reaction equations Furthermore, instead of using cups and teaspoons, we use moles Furthermore, instead of using cups and teaspoons, we use moles Last, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients Last, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients
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- Chemistry Recipes Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe)
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- Chemistry Recipes Be sure you have a balanced reaction before you start Be sure you have a balanced reaction before you start Example: 2 Na + Cl 2 2 NaCl Example: 2 Na + Cl 2 2 NaCl This reaction tells us that by mixing 2 moles of Na with 1 mole of Cl we will get 2 moles of sodium chloride This reaction tells us that by mixing 2 moles of Na with 1 mole of Cl we will get 2 moles of sodium chloride What if we wanted 4 moles of NaCl? 10 moles? 50 moles? What if we wanted 4 moles of NaCl? 10 moles? 50 moles?
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- Practice Write the balanced reaction for hydrogen gas reacting with oxygen gas. Write the balanced reaction for hydrogen gas reacting with oxygen gas. 2 H 2 + O 2 2 H 2 O 2 H 2 + O 2 2 H 2 O How many moles of reactants needed? What if we wanted 4 moles of water? What if we had 3 moles of O 2, how much H 2 would we need to react and how much water would we get? What if we had 50 moles of H 2 ?
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- Mole Ratios These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical Example: How many moles of chlorine is needed to react with 5 moles of sodium (without any sodium left over)? Example: How many moles of chlorine is needed to react with 5 moles of sodium (without any sodium left over)? 2 Na + Cl 2 2 NaCl 5 moles Na 1 mol Cl 2 2 mol Na = 2.5 moles Cl 2
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- Mole-Mole Conversions How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal? How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal?
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- Mole-Mass Conversions Example: How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? 2 Na + Cl 2 2 NaCl 5.00 moles Na 1 mol Cl 2 70.90g Cl 2 2 mol Na 1 mol Cl 2 = 177g Cl 2
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- Mole-Mass Conversions Most of the time in chemistry, the amounts are given in grams instead of moles Most of the time in chemistry, the amounts are given in grams instead of moles We still go through moles and use the mole ratio, but now we also use molar mass to get to grams We still go through moles and use the mole ratio, but now we also use molar mass to get to grams
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- Mass-Mole We can also start with mass and convert to moles of product or another reactant We can also start with mass and convert to moles of product or another reactant We use molar mass and the mole ratio to get to moles of the compound of interest We use molar mass and the mole ratio to get to moles of the compound of interest Calculate the number of moles of ethane (C 2 H 6 ) needed to produce 10.0 g of water Calculate the number of moles of ethane (C 2 H 6 ) needed to produce 10.0 g of water 2 C 2 H 6 + 7 O 2 4 CO 2 + 6 H 2 0 2 C 2 H 6 + 7 O 2 4 CO 2 + 6 H 2 0 10.0 g H 2 O 1 mol H 2 O 2 mol C 2 H 6 18.0 g H 2 O 6 mol H 2 0 = 0.185 mol C 2 H 6
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- Practice Calculate the mass in grams of Iodine required to react completely with 0.50 moles of aluminum. Calculate the mass in grams of Iodine required to react completely with 0.50 moles of aluminum.
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- Practice Calculate how many moles of oxygen are required to make 10.0 g of aluminum oxide Calculate how many moles of oxygen are required to make 10.0 g of aluminum oxide
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- Mass-Mass Conversions Most often we are given a starting mass and want to find out the mass of a product we will get (called theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients!) Most often we are given a starting mass and want to find out the mass of a product we will get (called theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients!) Now we must go from grams to moles, mole ratio, and back to grams of compound we are interested in Now we must go from grams to moles, mole ratio, and back to grams of compound we are interested in
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- Mass-Mass Conversion Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. N 2 + 3 H 2 2 NH 3 N 2 + 3 H 2 2 NH 3 2.00g N 2 1 mol N 2 2 mol NH 3 17.06g NH 3 28.02g N 2 1 mol N 2 1 mol NH 3 = 2.4 g NH 3
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- Practice How many grams of calcium nitride are produced when 2.00 g of calcium reacts with an excess of nitrogen? How many grams of calcium nitride are produced when 2.00 g of calcium reacts with an excess of nitrogen?
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- Limiting Reactant: Cookies 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen If we had the specified amount of all ingredients listed, could we make 4 dozen cookies? What if we had 6 eggs and twic

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