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Objectives SWBAT define stoichiometry. SWBAT write a mole ratio relating two substances in a chemical reaction. SWBAT calculate the mass of a reactant or product from the mass of a different reactant or product.

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Stoichiometry

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What is Stoichiometry? “To measure elements” The study of the quantitative relationship between the amounts of reactants and products in a chemical reaction. A balanced chemical equation can be interpreted in terms of particles, mass, and moles.

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To make a bike?

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iron + oxygen iron (III) oxide What is the balanced chemical equation? What does this tell us?

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Iron + Oxygen Iron (III) Oxide 4 Fe + 3 O 2 2Fe 2 O 3 4 atoms Fe + 3 molecules O 2 2 formula units Fe 2 O 3 4 moles Fe + 3 moles O 2 2 moles Fe 2 O 3 55.85g/mol × 4 = 223.40 g/mol + 32.00g/mol × 3 = 96.00g/mol 159.70g/mol × 2 = 319.40g/mol 223.40g/mol + 96.00g/mol = 319.40g/mol 319.40g/mol

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Mole Ratios Solving any reaction stoichiometry problem involves the use of a mole ratio A mole ratio is a conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction This information is obtained directly from the coefficients in a balanced chemical equation

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Mole Ratios – Examples Consider the following equation: 2 H 2 + O 2 → 2 H 2 O sample mole ratios: –2 mol H 2 = 2 mol H 2 O –1 mol O 2 = 2 mol H 2 O –2 mol H 2 = 1 mol O 2

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Sample Problem #1 Potassium and water react to form potassium hydroxide and hydrogen gas. How many moles of hydrogen are produced when 0.04 moles of potassium are used?

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Answer 0.02 mol H 2

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Sample Problem #2 Ammonium nitrate, an important fertilizer, produces dinitrogen monoxide and water when it decomposes. Determine the mass of the water produced from the decomposition of 25.0 g of ammonium nitrate.

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Answer 11.2 g H 2 O

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Answer 2.0 x 10 24 formula units of NaCl

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Announcement! Please remove your wonderful STEM posters by next Wednesday.

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Agenda Practice Problems Stoichiometry Worksheets

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Homework Stoichiometry Mole to Mole Probs Stoichiometry Mass to Mass Probs Stoichiometry Volume to Volume Probs

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Drill 3/6/14 List the number of conversion factors and type for mole-to-mole AND mass-to-mass conversion stoichiometry problems.

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Drill 3/6/14 Conversion factors/type for mole-to-mole AND mass-to-mass conversion problems. Mole-to-mole – 1 conversion factor = mole ratio (use coefficients of “given” and “TBD” Mass-to-mass – 3 conversion factors = 1.Formula mass 2.Mole ratio 3.Formula mass

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Homework Due – questions?? 11-2 Practice Probs WS – front side only Stoichiometry Practice #3

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Practice Problem How many grams of water are produced when 7.00 grams of oxygen (O 2 ) react with an excess of hydrogen according to the reaction shown below? 2 H 2 + O 2 → 2 H 2 O

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Answer 7.89 g water

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Practice Problems Laughing gas (N 2 O) is sometimes used as anesthetic in dentistry. It is produced when ammonium nitrate is decomposed according to the following reaction: NH 4 NO 3 (s) → N 2 O (g) + 2 H 2 O (l) How many moles of NH 4 NO 3 are required to produce 33.0 g N 2 O?

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Answer 0.750 mol NH 4 NO 3

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Practice Problem Acetylene gas (C 2 H 2 ) is produced as a result of the following reaction: CaC 2 + 2 H 2 O → C 2 H 2 + Ca(OH) 2 If 32.0 g of CaC 2 are consumed in this reaction, how many grams of water are needed?

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Answer 18.0 g water

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Practice Problem Milk of magnesia, a suspension of Mg(OH) 2 in water, reacts with stomach acid, HCl, in a neutralization reaction: Mg(OH) 2 + 2 HCl → 2 H 2 O + MgCl 2 How many formula units of MgCl 2 will be produced if 3.00 g of Mg(OH) 2 reacts?

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Drill #132/27 & 28/13 For the balanced equation shown below, how many moles of H 2 can be produced by 0.6351 moles of Al? mole to mole conversion 2 Al + 6 HCl → 2 AlCl 3 + 3 H 2

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Answer 0.9527 mol H 2

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Drill #143/1 & 3/4/13 Complete Empirical and Molecular Formula Drill

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Objectives SWBAT define stoichiometry. SWBAT write a mole ratio relating two substances in a chemical reaction. SWBAT calculate the mass of a reactant or product from the mass of a different reactant or product.

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Answer 3.10 x 10 22 formula units MgCl 2

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Drill #2/26/14 Nitrogen and hydrogen react to form ammonia. How many grams of hydrogen are needed to react with 50.0 g of nitrogen in this reaction? Mass to mass conversion

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Answer 10.7 g H 2

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