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OCTOBER 14 & 15 2013 MS. BOON CHEMISTRY Stoichiometry: Mole Ratios

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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 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.

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

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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 CuCl 2 3 Cu + 2 AlCl 3 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.

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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

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What is a mole ratio? 2 Mg + O 2 2 MgO 1.What is the ratio of moles Mg atoms to moles O 2 molecules? Write this ratio as a fraction: 2 mol Mg 1 mol O 2 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.

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White Board Practice #1 CH 4 + 2 O 2 CO 2 + 2 H 2 O 1.What is the ratio of moles CH 4 to moles O 2 ? 2.What is the ratio of moles O 2 to moles CO 2 ? 3.What is the ratio of moles H 2 O to moles CH 4 ? 4.What is the ratio of moles CO 2 to moles H 2 O? 1 mol CH 4 2 mol O 2 1 mol CO 2 2 mol H 2 O 1 mol CH 4 1 mol CO 2 2 mol H 2 O

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White Board Practice #2 Do the following problem on your white board. 2 NI 3 N 2 + 3 I 2 What is the mole ratio of NI 3 to N 2 ? Vote for your answer: 1) 1 mol NI 3 2 mol N 2 2) 2 mol NI 3 2 mol N 2 3) 2 mol NI 3 1 mol N 2 4) 3 mol NI 3 2 mol N 2

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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) 2 FeO + 1 C 2 Fe + 1 CO 2 2) 2 NO + 1 O 2 1 NO 2 3) 1 CH 4 + 4 S 1 CS 2 + 2 H 2 S Balance the equations and then give the ratio between the two compounds in bold red. 4)__PCl 3 +__H 2 O __H 3 PO 3 +__HCl 5)___Xe + ___F 2 ___XeF 4 6)__Al +__HCl __AlCl 3 +__H 2

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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?

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

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

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White Board Practice #1 CH 4 + 2 O 2 CO 2 + 2 H 2 O How many moles of CH 4 are needed to form 30 moles of H 2 O? Given: Unknown: Conversion Factor: Setup & Solve: 1 mol CH 4 2 mol H 2 O X 30 mol H 2 O = 15 mol CH 4

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

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

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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

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Exit Slip 2 KClO 3 (s) 2 KCl (s) + 3 O 2 (g) 1. What is the mole ratio of KCl to O 2 ? 2. What is the mole ratio of KCl to KClO 3 ? 3. How many moles O 2 will be produced from 4 moles KClO 3 ? 4. How many moles KClO 3 are required to produce 32 moles KCl?