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CA STANDARDS Std. 3e: Students know how to calculate the masses of reactants and products in a chemical reaction from the mass of one of the reactants or products and the relevant atomic masses.

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WHAT IS STOICHIOMETRY? The study of quantities of materials consumed and produced in chemical reactions.

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HOW ARE STOICH PROBLEMS DIFFERENT? Includes a balanced equation and molar conversions. Coefficient of equation shows molar relationship (Mole ratio) of reactants and products. Ex: 2H 2 + O 2 2H 2 O 2 mol H mol O 2 2 mol H 2 O Ex: Mole Ratio of H 2 : H 2 O 2 mol H 2 2 mol H 2 O

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CALCULATING MASSES OF REACTANTS AND PRODUCTS 1.Check if equation is balanced. 2.Convert mass(g) or volume(L) to moles, if necessary. 3.Set up mole ratios. 4.Use mole ratios to calculate moles of desired substituent. 5.Convert moles to mass or volume, if necessary. 1.Check if equation is balanced. 2.Convert mass(g) or volume(L) to moles, if necessary. 3.Set up mole ratios. 4.Use mole ratios to calculate moles of desired substituent. 5.Convert moles to mass or volume, if necessary.

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STOICH PROBLEM TYPE #1 Ex 1: How many moles of NH 3 can be produced when 4 moles of N 2 is reacted with excess H 2 ? N 2 + 3H 2 2NH 3 4 mol N 2 = 8 mol NH 3 2 mol NH 3 1 mol N 2

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Ex 2: 2N 2 + O 2 2N 2 O How many moles of N 2 must be reacted with excess O 2 to produce 10 moles of N 2 O? 10 mol N 2 O 2 mol N 2 2 mol N 2 O = 10 mol N 2

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GRAMS OF GIVEN TO GRAMS OF UNKOWN ROADMAP MEMORIZE!!! (Mole Ratio) g GIVEN mol GIVEN mol UnKnown g UNKNOWN mol GIVEN

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STOICH PROBLEM TYPE#2 Ex 3: 46 grams of Sodium (Na) reacts with an excess Chlorine (Cl). How many grams of Sodium Chloride (NaCl) are formed? 2Na + Cl 2 2NaCl = 46 g Na 116 g NaCl 1 mol Na 23 g Na 2 mol Na 2 mol NaCl 1 mol NaCl 58 g NaCl

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Ex 4: How many grams of water can be prepared from 8 grams of hydrogen at standard conditions? 2 H 2 (g) + O 2 (g) 2 H 2 O 8 g H 2 = 72 g H 2 O 1 mol H 2 2 g H 2 2 mol H 2 O 2 mol H 2 1 mol H 2 O 18 g H 2 O

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GAS STOICHIOMETRY If reactants and products are at the same conditions of temperature and pressure, then mole ratios of gases are also volume ratios. 3 H 2 (g) + N 2 (g) 2NH 3 (g) 3 moles H mole N 2 2 moles NH 3 3 liters H liter N 2 2 liters NH 3

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GAS STOICHIOMETRY Ex 5: How many liters of NH 3 can be produced when 12 liters of H 2 react with an excess of nitrogen? 3 H 2 (g) + N 2 (g) 2NH 3 (g) 12 L H 2 L H 2 = L NH 3 L NH

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Ex 6: How many liters of oxygen are required to react completely with 22.4 liters of carbon monoxide, CO, at standard conditions? 2 CO (g) + O 2 (g) 2 CO 2 (g) 22.4 L CO L CO = L O 2 L O

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END OF UNIT 3: Woo Hoo!

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EVERYDAY STOICH Smores: G 2 + C + M G 2 CM + + How many Smores can I make with 5 Graham crackers, 3 marshmallows and 1 Chocolate?

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