Agenda: 4/21

1. Homework: Complete practice problems Agenda: 4/21 Objective: To determine quantities needed for chemical reactions in research or manufacturing: Stochiometry Review: Set up of Stoichiometry Problems Graphic Organizer for Stoichiometry Class Practice: Mixed Problems Percent Yield – Practice Problems Mixed Stoichiometry Practice Problems - Pairs

2. Essential to StoichiometrySet-up of problems The mole ratio is the heart of the stoichiometry calculation

3. Mole Ratio The heart of the stochiometry calculation. Mole ratio: Mole Unknown Mole Given Mole ratio: Used the coefficients of a balanced chemical equation

4. Graphic organizer Mole Ratio Mole________ Mole Volume of a Gas Volume of a Gas Mass Mass X Mole Mole Particles Particles

5. Putting all the steps together in a stoichiometry calculation

6. Putting all the steps together in a stoichiometry calculation • Propane (C₃H₈) reacts with oxygen to produce carbon dioxide and water vapor. • Balanced equation:

7. Example 1: • How many moles of oxygen are required to completely react 10 moles of propane?

8. Example 1: • How many moles of oxygen are required to completely react 10 moles of propane?

9. Example 2: • How many grams of oxygen are required to completely react 10 moles of propane? Molar mass of oxygen:

10. Example 3: • How many liters of oxygen are required to completely react 10 moles of propane? 1 mole of oxygen at STP = ____________ liters

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

12. 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” Molar mass of magnesium:

13. 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? Molar mass of magnesium: Molar mass of magnesium chloride:

14. Example 6: • How many liters of Hydrogen gas will be produced with 60 grams of hydrochloric acid and an excess of magnesium? Molar mass of hydrochloric acid: 1 mole of hydrogen gas at STP:

15. 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.

16. Percent Yield • Percent yield: Actual Yield x 100 = % Theoretical Yield • In the last stoichiometry problem, 661.5 grams of sulfuric acid was calculated. However, the sample was weighed and found to be 650.7 grams. The percent yield is: ______________ x 100 = % Note: the % yield is always less than 100%

17. Percent Yield Calculations 1)Balance this equation and state which of the six types of reaction is taking place: ____ Mg + ____ HNO3 ____ Mg(NO3)2 + ____ H2 Type of reaction: __________________________ 2)If I start this reaction with 40 grams of magnesium and an excess of nitric acid, how many grams of hydrogen gas will I produce? 3)If 1.7 grams of hydrogen is actually produced, what was my percent yield of hydrogen?

18. 4)Balance this equation and state what type of reaction is taking place: ____ NaHCO3 ____ NaOH + ____ CO2 Type of reaction: __________________________ 5) If 25 grams of carbon dioxide gas is produced in this reaction, how many grams of sodium hydroxide should be produced? 6) If 50 grams of sodium hydroxide are actually produced, what was my percent yield?

19. Check answers 1) Balance this equation and state which of the six types of reaction is taking place: 1Mg + 2 HNO31 Mg(NO3)2 + 1H2 Type of reaction: single displacement 2) If I start this reaction with 40 grams of magnesium and an excess of nitric acid, how many grams of hydrogen gas will I produce? 3.3 grams (when Mg atomic mass = 24.3 grams) 3) If 1.7 grams of hydrogen is actually produced, what was my percent yield of hydrogen? 52% 4)Balance this equation and state what type of reaction is taking place: 1NaHCO31NaOH + 1CO2 Type of reaction: decomposition 5) If 25 grams of carbon dioxide gas is produced in this reaction, how many grams of sodium hydroxide should be produced? 22.7 grams NaOH 6)If 50 grams of sodium hydroxide are actually produced, what was my percent yield? 50/22.7 x 100% = 220% Hopefully, you understand that this is not a reasonable answer to this question and indicates that something very wrong happened during this reaction.

20. Manufacturing Sulfuric Acid Using stoichiometry in an industrial application

21. 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 H₂SO₄. The company is expecting a shipment of 500 kg of SO₂ and wants to know how much H₂SO₄ can be made from this shipment.

22. What are the steps to determine the amount of sulfuric acid? 1. 2. 3.

23. 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 SO₂.

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