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Stoichiometry: Mole Ratios

Stoichiometry: Mole Ratios. October 14 & 15 2013 Ms. Boon Chemistry. Think Box A cookie recipe requires 1 cup of sugar, 2 cups of flour, 1 stick of butter and 3 eggs. How much of each ingredient do you need in order to double the recipe? Explain your answer. Objective:

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Stoichiometry: Mole Ratios

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  1. Stoichiometry: Mole Ratios October 14 & 15 2013 Ms. Boon Chemistry

  2. Think Box • A cookie recipe requires 1 cup of sugar, 2 cups of flour, 1 stick of butter and 3 eggs. • How much of each ingredient do you need in order to double the recipe? Explain your answer. Objective: I can create mole ratios from a balanced chemical equation and perform mole to mole conversions. Agenda: Catalyst One-Step Stoichiometry Quiz Notes and Practice: Mole Ratios Game: Reactants, Products, and Leftovers

  3. Mini Review: What is stoichiometry? Stoichiometry is the study of the relationships between quantities of substances in chemical reactions.

  4. Where are we going with this? Next week you will do a lab where you will be asked to answer questions like the one below: When aluminum foil is dipped in copper (II) chloride a displacement reaction takes place: 2 Al + 3 CuCl2→ 3 Cu + 2 AlCl3 If you dip a 10 g piece of aluminum foil into 20 mL of 0.1 M cupper chloride, how many grams of copper metal will form? To solve this problem, we need to learn how to use a mole ratio.

  5. Think, Pair, Share: Cookie Recipe Ratios. A "ratio" is just a comparison between two different things. Look at the cookie recipe in the think box above. List the following ratios as fractions in the space below: (a) sugar to flour (b) flour to butter (c) eggs to butter (d) eggs to sugar (e) butter to flour

  6. What is a mole ratio? • Mole ratios are used to compare the amounts of reactants and products in a balanced chemical reaction equation. • The coefficients represent the number of moles. • Mole ratios are conversion factors in stoichiometry problems. 2 Mg + O2 2 MgO • What is the ratio of moles Mg atoms to moles O2 molecules? • Write this ratio as a fraction: 2 mol Mg • 1 mol O2

  7. White Board Practice #1 CH4 + 2 O2 → CO2 + 2 H2O 1 mol CH4 2 mol O2 What is the ratio of moles CH4 to moles O2? What is the ratio of moles O2 to moles CO2? What is the ratio of moles H2O to moles CH4? What is the ratio of moles CO2 to moles H2O? 2 mol O2 1 mol CO2 2 mol H2O 1 mol CH4 1 mol CO2 2 mol H2O

  8. White Board Practice #2 Do the following problem on your white board. 2 NI3 N2 + 3 I2 What is the mole ratio of NI3 to N2? Vote for your answer: 2) 2 mol NI3 2 mol N2 1) 1 mol NI3 2 mol N2 4) 3 mol NI3 2 mol N2 3) 2 mol NI3 1 mol N2

  9. More White Board Practice Complete the following problems in your notes. Give the mole ratio between the two compounds that are in bold red.1) 2FeO + 1 C  2 Fe + 1CO2 2) 2 NO + 1O2 1NO2 3) 1 CH4 + 4S 1 CS2 + 2H2S Balance the equations and then give the ratio between the two compounds in bold red. 4)__PCl3 +__H2O __H3PO3 +__HCl 5)___Xe + ___F2  ___XeF4 6)__Al +__HCl__AlCl3 +__H2

  10. Mole to Mole Conversion Problems: In most chemistry lab problems involving stoichiometry, you will know or be able to find out via measurement information about one reactant or product. Based on this information, you will be asked to make calculations to determine the amounts of a different reactant or product. Mole to mole conversions are at the heart of this idea. Example: You react copper wire with silver nitrate. How much silver nitrate is needed to form 5 g of silver metal as the product?

  11. Mole to Mole Conversions: Example 1 2 Mg + O2 2 MgO How many moles of MgO can be made from 12 moles of Mg? Given: 12 mol Mg Unknown: molMgO Conversion Factor: 2 molMgO/ 2 mol Mg Setup & solve: X = 12 mol Mg 2 mol MgO 2 mol Mg 12 mol MgO

  12. Mole to Mole Conversions: Example 2 2 Mg + O2 2 MgO How many moles of Mg are required to produce 8 moles MgO? Given: 8 molMgO Unknown: mol Mg Conversion Factor: 2 mol Mg/ 2 molMgO Setup & solve: X = 8molMgO 2 mol Mg 2 molMgO 8mol Mg

  13. White Board Practice #1 CH4 + 2 O2 → CO2 + 2 H2O How many moles of CH4 are needed to form 30 moles of H2O? Given: Unknown: Conversion Factor: Setup & Solve: X 1 mol CH4 2 mol H2O = 30 mol H2O 15 mol CH4

  14. White Board Practice #2 Do the following problem in your notes. 2 NI3 N2 + 3 I2 How many moles NI3 are required to produce 10 moles N2? Vote for your answer: 2) 20 mol NI3 1) 10 mol NI3 4) 40 mol NI3 3) 5 mol NI3

  15. Mole to Mole Conversion Practice Complete the worksheet problems on your notes. Work quietly with the people around you. Show all your work. Tonight’s HW: Read p. 302 – 305; Do practice problems p. 304 #1 & 2, p. 311 #1, 4(a), 6.

  16. Game: Reactants, Products, Left Overs Work with a partner. Show work on your white board. The purpose of the game is to determine the amounts of reactants, products, or left overs based on the given information. http://phet.colorado.edu/en/simulation/reactants-products-and-leftovers

  17. Exit Slip 2 KClO3 (s) → 2 KCl (s) + 3 O2 (g) What is the mole ratio of KCl to O2? What is the mole ratio of KCl to KClO3? How many moles O2 will be produced from 4 moles KClO3? How many moles KClO3 are required to produce 32 moles KCl?

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