Stoichiometry Calculating quantities needed in a chemical reaction 1

Importance of stoichiometry Essential Learning Manufacturing – Pharmaceuticals, plastics, detergents, cosmetics, fibers and dyes, fertilizers, etc. – How much materials are needed to meet customer orders? – How much starting material must be ordered or made? Research: Tracking a predicted reaction based on the amount of product 2

3 Essential to Stoichiometry Set-up of problems Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit The mole ratio is the heart of the stoichiometry calculation

Important foundation knowledge for stoichiometry Mole Conversion Balancing chemical equations Writing correct formulas: – Word equations – Names & formulas 4

Essential to Stochiometry Mole conversions 5 Mole

Stoichiometry Calculations to determine the __________ of products produced or the ___________ of reactants needed in a chemical reaction. (A) Stoichiometry calculations MUST have (1) (2) 6

B. Balanced equations are the ___________ for the chemical reactions. C. Stoichiometry calculations always use only ________ substances in the reaction. You assume that there is a sufficient amount of other substances to react. 7

Mole Ratio 8 Mole ratio: tells the correct proportions of substances for a chemical reaction.

Mole ratio: Starts with a balanced equation _ H ₂SO₄+__ NaOH →__ Na ₂SO₄+__ H ₂0 H ₂SO₄ NaOH Na ₂SO₄ H ₂0 Name # molecules # moles 9

Writing a Mole Ratio: Always use the _____________ of a ______________ equation. Always in a calculation, write: Mole:___________ Mole: 10

Writing the mole ratio: 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 GivenMole RatioUnknown H ₂SO₄ Na ₂SO₄ H ₂SO₄ H ₂0 NaOH Na ₂SO₄ NaOH H ₂0 H ₂SO₄ Na ₂SO₄ NaOH 11

Types of Stoichiometry Problems Mole Mass Volume Combinations of above (mixed problems) Particles (compounds, molecules, atoms) Only sometimes 12

III. Mole to Mole Stoichiometry Problems Need ______________ equation Need ______________ ratio Given xMole Ratio= Unknown Amount of given substance in moles mole unknown mole given = Amount of unknown substance in moles 13 X

Mole to Mole Calculations 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 How many moles of water will be produced if there are 10 moles of sodium hydoxide? How many moles of sulfuric acid are required if 135 moles of sodium sulfate must be produced? 14

Mole to Mole Calculations 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 How many moles of sodium hydroxide must be available to produce 17 moles of sodium sulfate? 15

Review: How many moles are in 120 grams of Sodium Sulfate? Formula for sodium sulfate Molar mass of sodium sulfate Mole conversion 16

Review: Mole to Mole Calculations How many moles of hydrochloric acid must be available to produce 20 moles of magnesium chloride? 17 Hydrochloric acid reacts with magnesium to yield magnesium chloride and hydrogen

IV. Gram to Gram Calculations Must use molar mass conversions – Molar mass means: – Use the ____________ ____________ GivenConversionMole RatioConversionUnknown Mass of given substance (grams) X 1 mole Molar mass of given X Mole unknown Mole Given X Molar mass of unknown 1 mole = Mass of unknown substance 18

Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 Must determine the molar mass (grams) H ₂SO₄ NaOH Na ₂SO₄ H ₂0 Molar mass (grams of 1 mole) 19

Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 If 600 grams of sodium sulfate are required, how many grams of sodium hydroxide must be used? 20

Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 If 325 grams of sodium sulfate are required, how many grams of sulfuric acid must be used? 21

Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 If 540 grams of sodium hydroxide are available, how much sodium sulfate ( in grams) will be produced? 22

Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 If 540 grams of sodium hydroxide are available, how many grams of sulfuric acid must be used? 23

Silent Lunch Why? Poor clean-up of the cafeteria – Expectation: You are responsible that all trash is properly thrown away What: Silence – Walk down together to cafeteria in silence – Sit together in silence – All trash is thrown away and area is cleaned Failure to comply starts with ASD 24

Agenda – Dec. 3 rd Warm-up: Stoichiometry preparation & practice Stoichiometry – Graphic organizer – Practice problems – individual, pair or team – Percent Yield Analysis of chemical reaction problems Mole conversion practice 25

2 Li(OH)(s) + CO ₂(g) → Li₂CO₃(s)+ H₂O(l) Solid lithium hydroxide is used in the space shuttle to remove excess carbon dioxide from the living areas. Show the problem set-up for each problem. Remember to label all quantities with units and formulas. 1.How many moles of lithium hydroxide are required to react with 15 moles of carbon dioxide? 2.If 200 grams of carbon dioxide must be removed each day, how many grams of lithium hydroxide are needed per day of the space voyage? 26

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Mole to Gram Calculation 2 Li(OH)(s) + CO ₂(g) → Li₂CO₃(s)+ H₂O(l) If 10 moles of lithium hydroxide are available, how many grams of water will be produced? 28

Gram to Liter Calculation 2 Li(OH)(s) + CO ₂(g) → Li₂CO₃(s)+ H₂O(l) If 100 grams of lithium hydroxide are available, how many liters of carbon dioxide must be used? 29

Help for Stoichiometry Problems Foldable Graphic organizer Shows: – Mole ratio as heart (center) of all calculations – Given and Unknown – Mole conversions 30

Graphic organizer 31 Mole Ratio Mole________ Mole X

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Practice problems Teacher led Partners Alternate problems with calculations One student calculates the problem & then explains how she/he did it to the other student. (Why? The process of explaining helps you in gaining and retaining the information.) 35

NO + O ₂→ NO₂ 36 NO O₂O₂ NO ₂ # moles Molar mass

CS ₂ + O₂→ CO₂ + SO₂ 37 CS ₂ O₂O₂ CO ₂ SO ₂ # moles Molar mass (g)

Review: Gram to Gram Calculation 1 H ₂SO₄+ 2 NaOH → 1 Na ₂SO₄+ 2 H ₂0 If 540 grams of sodium hydroxide are available, how many grams of sulfuric acid must be used? 38

Percent Yield Stoichiometry calculations always give the maximum amount that can be produced. This is called the _________ ________. In real life, the maximum amount is never produced. Reactions do not proceed perfectly. The _________ ________ is produced. 39

Percent Yield Percent yield: Actual Yield x 100 = % Theoretical Yield In the last stoichiometry problem, grams of sulfuric acid was calculated. However, the sample was weighed and found to be grams. The percent yield is: ______________ x 100 = % Note: the % yield is always less than 100% 40

Analysis of Chemical Reaction problems 41

Putting all the steps together in a stoichiometry calculation Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 42

Putting all the steps together in a stoichiometry calculation Propane (C ₃H₈) reacts with oxygen to produce carbon dioxide and water vapor. Balanced equation: 43

Example 1: How many moles of oxygen are required to completely react 10 moles of propane? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 44

Example 1: How many moles of oxygen are required to completely react 10 moles of propane? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 45

Example 2: How many grams of oxygen are required to completely react 10 moles of propane? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 46 Molar mass of oxygen:

Example 3: How many liters of oxygen are required to completely react 10 moles of propane? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 47 1 mole of oxygen at STP = ____________ liters

Magnesium reacts with hydrochloric acid to yield magnesium chloride and hydrogen gas. Balanced equation: 48

Example 4: How many moles of magnesium chloride will be produced if a chemist starts with 120 grams of magnesium metal and plenty* of hydrochloric acid? *Chemistry language: “with an excess of hydrochloric acid” Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 49 Molar mass of magnesium:

Example 5: How many grams of magnesium chloride will be produced if a chemist starts with 60 grams of magnesium metal and an excess of hydrochloric acid? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 50 Molar mass of magnesium:Molar mass of magnesium chloride:

Example 6: How many liters of Hydrogen gas will be produced with 60 grams of hydrochloric acid and an excess of magnesium? Given: Amount & Unit Do I need to convert the given to moles? Mole RatioDo I need to convert from moles to another unit? Unknown: Unit 51 Molar mass of hydrochloric acid:1 mole of hydrogen gas at STP:

Manufacturing Sulfuric Acid Using stoichiometry in an industrial application 52

53 Here is a typical problem: Sulfuric acid, an important chemical in industry, is manufactured and sold by XYZ company. Sulfur dioxide gas is combined with water and oxygen to make H ₂ SO ₄. The company is expecting a shipment of 500 kg of SO ₂ and wants to know how much H ₂ SO ₄ can be made from this shipment.

What are the steps to determine the amount of sulfuric acid?

Determining sales value They can then calculate how much money they will make from the sale of their sulfuric acid. Water and oxygen are readily available and cheap, so the company uses an EXCESS of these substances, which means they use more than enough to react with the SO ₂. 55

Sales If you can sell sulfuric acid for $10 per kg, how much will be the total sales ($)? 56