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My Favorite “No”

My Favorite “No”. Today you will need goggles and a lab apron. Write the balanced chemical equation: When heated NaHCO 3 reacts to form sodium carbonate, carbon dioxide, and water. Investigation: All That Remains.

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My Favorite “No”

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  1. My Favorite “No” Today you will need goggles and a lab apron. Write the balanced chemical equation: When heated NaHCO3 reacts to form sodium carbonate, carbon dioxide, and water.

  2. Investigation: All That Remains Predict the outcome and then test your prediction: How much solid mass will remain after decomposing 2.00g of sodium hydrogen carbonate by heating? (Hint: 2NaHCO3(s) -> Na2CO3(s) + CO2(g) + H2O(g)) Spend 5 minutes working on your prediction, design, and safety considerations with your group.

  3. Investigation: All That Remains Class Discussion After class discussion, write any changes to your original procedure and begin your experiment. Once you have completed the experiment, answer the questions at the bottom of page 2.

  4. Homework Complete page 2 and the pre-lab on page 4.

  5. My Favorite “No” Today you will need goggles and a lab apron. How many moles of carbon dioxide are in a 226 L sample of CO2?

  6. Mole Review • For conversions between mass, volume (of a gas), and number of particles, we use the _________to guide our _________________. mole map dimensional analysis

  7. Dimensional Analysis Review With dimensional analysis, multiply the given by one or more conversion factors in the form of a fraction. Example: 12 donuts = 1 dozen donuts 36 donuts 1 36 donuts = =

  8. Chemical Conversion Factors 1 mole = molar mass (g) 1 mole = 6.02 x 1023 particles (atoms, ions, molecules, f.un.) 1 mole = 22.4L of a gas at STP

  9. Practice Problems 1. What is the mass of 4 moles of oxygen gas? 2. What is the volume of 3.4 x 1025 molecules of CH4 at STP?

  10. Cu-Fe Lab • In this lab exercise, iron nails will react with a solution of copper (II) chloride to produce iron (II) chloride and copper. When the reaction is complete, the mass of iron used as a reactant and the mass of copper metal produced will be determined. • Then using the process of stoichiometry, the theoretical yield of copper can be calculated, followed by a percent yield calculation to determine the efficiency of this chemical reaction.

  11. Cu-Fe Lab Purpose: To use stoichiometry to predict the amount of copper produced. To calculate the percent yield of copper using the actual yield found by experimentation. Safety: 1) Wear safety goggles and lab aprons at all times. 2) All acid spills should be neutralized with baking soda (NaHCO3).

  12. Cu-Fe Lab Day 1 Supplies per group: 100 mL beaker (and tape to label) 4.25g copper II chloride 2 iron nails Sandpaper 25 mL graduated cylinder Stirring rod

  13. Homework Complete page 5

  14. 1/28 Warm-Up: Balancing Chemical Equations (Page 6) • Directions: Using coefficients, balance the following equation - ____ C6H6 + ____O2 → ____CO2 + ____H2O 2 15 12 6

  15. Cooking Analogy – Click Here • Grill Master K.T. Tigers has the art of grilled cheese sandwich making down to a science. The Grill Master's recipe requires 2 pieces of cheese between 2 slices of bread, grilled to perfection. What is the coefficient ratio of the ingredients to the product? 2 2 1

  16. Cooking • Grill Master Tigers knows that a 20 pack of sliced bread and a 20 pack of sliced cheese will always make the same number of grilled cheese sandwiches with no leftovers. How many? • 2 slices of bread and 2 slices of cheese per sandwich will make 10 sandwiches without any leftover ingredients • What happens to the Grill Master's grilled cheese sandwiches if he changes the quantities of ingredients? Will he have enough ingredients? Will there be leftovers? • Changing the quantity of any single ingredient will change the number of sandwiches the Grill Master can produce • If all ingredients are not changed in the same proportion, one or more ingredients will be leftover, or in excess • Practice grilled cheese sandwich making here: http://phet.colorado.edu/en/simulation/reactants-products-and-leftovers

  17. What Cooking Really Is… Stoichiometry: • The calculation of quantities in chemical reactions. Example: N2 (g) + 3H2 (g) → 2NH3 (g) • The coefficient ratio of substances in this balanced chemical equation is 1 : 3 : 2 • It states, 1 molecule of nitrogen gas reacts with 3 molecules of hydrogen gas to yield 2 molecules of ammonia gas • OR – 1 mol of nitrogen gas reacts with 3 mol of hydrogen gas to yield 2 mol of ammonia gas; etc.

  18. Instead of cups, teaspoons, or tablespoons, we have… • 1. Representative Particles: • 1 molecule of nitrogen gas reacts with 3 molecules of hydrogen gas to produce 2 molecules of ammonia gas. • It's always in the same coefficient ratio; just like 2 slices of bread plus 2 slices of cheese produce 1 grilled cheese sandwich! • 2. Moles: • 1 mol of nitrogen gas reacts with 3 mols of hydrogen gas to produce 2 mols of ammonia gas.

  19. And… • 3. Mass: • Law of conservation of mass says mass of reactants must equal mass of products. • Mass of nitrogen gas = 28g and mass of hydrogen gas = 6g • The sum equals the mass of the products = 34.0g • 4. Volume: • 1 mol of gas = 22.4 L @ STP • 22.4 L of nitrogen gas reacts with 67.2 L of hydrogen gas to produce 44.8 L of ammonia.

  20. Mol to Mol Conversion Calculations • N2(g) + 3H2 (g) 2NH3 (g) • What is the mole ratio of the above equation? • 1 : 3 : 2 • Because we know the ratio, we can calculate to find the number of moles of another substance.

  21. Example • How many mols of NH3 are produced when 0.60 mol of nitrogen gas reacts with hydrogen gas? (show work) • 1.2 mol NH3

  22. Practice Problems MnO2 + 4HCl → MnCl4 + 2H2O 1. How many mol of H2O are produced when 3.20 mol of MnO2 reacts with hydrochloric acid? (show work)

  23. Practice Problems MnO2 + 4HCl → MnCl4 + 2H2O 2. How many mol of HCl are consumed (used) when 1.65 mol of Manganese (IV) chloride are produced? (show work)

  24. Practice Problems MnO2 + 4HCl → MnCl4 + 2H2O 3. How many mol of water are produced when 4.35 moles of MnCl4 are also produced? (show work)

  25. End of Day One of StoichiometryHomework: Page 8 Don’t worry, there will be more to come… 

  26. My Favorite “No” How many moles of H2 are in a 5.40g sample of H2? You will need a calculator and periodic table today!

  27. Remember this? Well, now that you know how to convert from moles of one substance to moles of another, we can expand it!

  28. The Mole Highway RECALL: The Mole Highway...it's been expanded and construction is complete! Like before, the Mole Highway can be used as a map toward setting up an appropriate conversion.

  29. The Mole Highway HOW IT’S USED: 1. Find the starting point; use the value, substance, and unit you are given 2. Find the ending point; use the value, substance, and unit are you being required to solve 3. You must stay on the highway!!! 4. Each road taken represents 1 step in your conversion! 5. Once the destination is reached, solve mathematically by multiplying across the top, multiplying across the bottom, and dividing the top value by the bottom value.

  30. The Mole Highway NOTES FOR USE: 1. Before any math can be done, a BALANCED CHEMICAL EQUATION is required. 2. If the starting value isn't in the unit "mol," your first step is to convert it there. 3. Going from mol of substance A to mol of substance B requires a Mol to Mol conversion; USE YOUR COEFFICIENTS FROM THE BALANCED CHEMICAL EQUATION!

  31. Mass – Mass Calculations N2(g) + 3H2 (g) → 2NH3 (g) • Like yesterday, in order to go from the mass of one substance, to the mass of a new substance, a mol to mol conversion will be necessary. • Steps, from a plan of action: • Mass A → Mol A → Mol B → Mass B • Convert from mass of substance A to mol of substance A • Convert from mol of substance A to mol of substance B • Convert from mol of substance B to mass of substance B • USE THE MOLE HIGHWAY!

  32. Example N2(g) + 3H2 (g) → 2NH3 (g) • Calculate the number of grams of NH3 produced by the reaction of 5.40 g of H2 with excess N2 (g). (show work) • 31.0 g NH3 (g)

  33. Practice Problems 1. How many grams of O2 (g) are produced when a sample of 29.2 g of water decomposes? • Write a balanced formula. • 2H2O → 2H2 + O2 • Get a plan of action: • g water → mol water → mol O2→ g O2 • (show work)

  34. Practice, con’t. 2. Using the same equation, how many liters of hydrogen gas are produced when 1.33 x 1017 molecules of water decompose? (show work)

  35. Practice, con’t. 2SO2 (g) + O2 (g) → 2SO3 (g) 3. How many liters of O2 are needed to produce 19.8 L of SO3? (show work)

  36. Practice, con’t. 4. How many molecules of oxygen are consumed in the formation of 187.4 L of SO3? (show work)

  37. Practice, con’t. 5. How many molecules of Sulfur dioxide are consumed in the formation of 4.41 x 1027 molecules of sulfur trioxide? (show work)

  38. End of Day TwoHomework: Page 11 Do not be sad Petry, lots of things cannot fly: rocks, trees, sticks, Spike! Don’t worry folks, if you aren’t there yet, you’ll learn how to fly in stoichiometry. 

  39. Section 9.3-Limiting Reagent First back to cooking… • What is Grill Master Tiger‘s recipe for grilled cheese sandwiches? • 2 slices of bread with 2 slices of cheese, grilled to perfection • What happens if the Grill Master receives only half of his order of cheese for the day? • He can only make half as many sandwiches, or he’ll have to modify his recipe. • So, in this case, what is limiting the number of grilled cheese sandwiches he can make? • The number of slices of cheese; it is his limiting ingredient, while the bread is his excess ingredient. • What if the Grill Master received 3 times the amount of cheese he needed? • He’d have left over cheese, it would be the excess ingredient. • What would be limiting him in this case? • The bread; there wouldn’t be enough bread to use all of the excess cheese.

  40. Limiting Reagent/Reactant • The same thing applies to chemical reactions… • N2(g) + 3H2 (g) 2NH3 (g) • 1 mol of N2(g) reacts with 3 mol of H2 (g) mol to form 2 mols of NH3 (g). • What happens if you only have 0.5 mol of nitrogen gas? • How much hydrogen gas would you use? • How much ammonia would you make?

  41. Limiting Reagent • Limiting Reagent: • Limits or determines the amount of product that can be formed in a reaction. • Excess Reagent: • The reactant that is not completely used up in a reaction.

  42. Example Problem • Sodium chloride can be prepared by the reaction of sodium metal with chlorine gas. Suppose that 6.70 mol of Na reacts with 3.20 mol of Cl2. What is the limiting reagent?

  43. Step 1: Write a balanced equation • 2Na (s) + Cl2 (g) 2NaCl (s)

  44. Step 2: Solve for moles of product for each reactant • To do this, convert the given info for each reactant (mol, in this problem) to mol of product. • If the original substances are given in grams, you’d have an extra step – converting mass to moles – but the rest of the process would be the same.

  45. Step 3: Determine the max. mol of product that can be made • You will have two answers for moles of product Why? There will be one for each reactant calculation. • So which one do I use? The smaller one • The SMALLER of the two answers is the maximum product because you only have enough reactants to make that amount. You will run out of one of the reactants before the larger amount is made.

  46. Step 4: Identify the limiting and excess reactants • Once you know your maximum product, look all the way to the left of that calculation. The reactant that produced that smaller amount of product is your limiting reactant. • It “limited” you to making the smaller of the two amounts! • The other reactant – that started the other calculation – is the excess reactant.

  47. Step 5: Solve your problem! • Convert mol of your limiting reagent to mol of product (or whatever the original question asks for).

  48. Sample Problem • 2Cu(s) + S(s) Cu2S(s) • 1. What is the limiting reagent when 80.0g Cu reacts with 25.0 g of S? • 2. What is the maximum number of grams of copper (I) sulfide produced? • Cu is the limiting reagent and S is in excess. • 100.23 g Cu2S

  49. End of Day Three I’ll Be Back…

  50. Percent Yield Cooking, yet again…  • Grill Master Tiger‘s recipe yields 10 grilled cheese sandwiches when 20 slices of bread and 20 slices of cheese are used • So, the recipe tells you the theoretical yield: • 10 sandwiches if followed specifically • What you actually make is the actual yield: • What if the pack of cheese only had 19 slices? Actual yield, 9 sandwiches. • What if you cut the ingredients in half? You’d actually yield 20 sandwiches.

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