1 / 84

Stoichiometry

Stoichiometry. Definition- the study of quantitative relationships between reactants and products. Using the Right Amount of reactants to make the Right Amount of Products Why is it important?. Stoichiometry.

dfarber
Download Presentation

Stoichiometry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Stoichiometry • Definition- the study of quantitative relationships between reactants and products. • Using the Right Amount of reactants to make the Right Amount of Products • Why is it important?

  2. Stoichiometry • Definition- the study of quantitative relationships between reactants and products. (Right Amount) • Why is it important? Saves money • Chemicals are expensive, • chemist need to know how much reactant to use in order to get a specific amount of product. • In industry or business in which chemicals are used to get a product it has to be efficiently otherwise money is wasted.

  3. Stoichiometry is like a Recipe? 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen • The ingredients are like reactants • Use the right amount of reactants to get right amt. product • The cookies are like products in a chemical reaction

  4. Stoichiometry is like a Recipe? 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen • To make good cookies you must follow the exact proportions or ratios of the recipe its all about the right measured amounts • If the recipe calls for 1 cup of butter to make 3 dozen cookies what would happen if you added 3 cups of butter?

  5. Chocolate Chip Cookie Recipe 1 cup butter 1/2 cup white sugar 1 cup packed brown sugar 1 teaspoon vanilla extract 2 eggs 2 1/2 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 2 cups semisweet chocolate chips Makes 3 dozen How many eggs are needed to make 3 dozen cookies? How much butter is needed for the amount of chocolate chips used? How many eggs would we need to make 9 dozen cookies? How much brown sugar would I need if I had 1 ½ cups white sugar?

  6. Recipes and Stoichiometry how are they different? • Instead of using cups and teaspoons, we use moles • Lastly, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients

  7. Chemistry Recipes • Looking at a balanced reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) • Be sure you have a balanced reaction before you start! Ex. 2 Na + Cl2  2 NaCl • This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride • What if we wanted 4 moles of NaCl? 10 moles? 50 moles?

  8. Chemistry Recipes • Looking at a balanced reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) • Be sure you have a balanced reaction before you start! Ex. 2 Na + Cl2  2 NaCl • This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride • What if we wanted 4 moles of NaCl? Need 4 mol Na & 2 Cl2 10 moles? 10 mol Na and 5 mol Cl2 50 moles? 50 mol Na and 25 mol Cl2

  9. If I wanted to make 9 moles CO2 how many moles of C3H8 do I need? • First make sure chemical equation is Balanced • Next interpret chemical equation. Ex: 1 C3H8 + 5O2 3CO2 + 4H2O • Coefficients indicate # of moles of each compound • 1mole C3H8 + 5 moles O2 3 moles CO2 + 4 moles H2O • Therefore you need 5 moles of oxygen for every 1 mole C3H8 to make 3 moles carbon dioxide 9 moles CO2 x 1 mole C3H8 = 3 moles C3H8 3 moles CO2

  10. If I wanted to make 9 moles CO2 how many moles of C3H8 do I need? • First make sure chemical equation is Balanced • Next interpret chemical equation. Ex: 1 C3H8 + 5O2 3CO2 + 4H2O • Coefficients indicate # of moles of each compound • 1mole C3H8 + 5 moles O2 3 moles CO2 + 4 moles H2O • Therefore you need 5 moles of oxygen for every 1 mole C3H8 to make 3 moles carbon dioxide 9 moles CO2 x 1 mole C3H8 = 3 moles C3H8 3 moles CO2 Mole Ratio comes from balanced equation

  11. Mole Ratios • Definition- ratio between the numbers moles of any 2 substances in a balanced chemical equation. 2Al + 3Br2 2AlBr3 2mol Al / 3 mol Br2 2mol Al / 2 mol AlBr3 3mol Br2 / 2 mol Al 3mol Br2 / 2 mol AlBr3

  12. Mole Ratios • Definition- ratio between the numbers moles of any 2 substances in a balanced chemical equation. 2Al + 3Br2 2AlBr3 How many moles of Br2 are needed to make 10 moles of AlBr3?

  13. Mole Ratios • Definition- ratio between the numbers moles of any 2 substances in a balanced chemical equation. 2Al + 3Br2 2AlBr3 How many moles of Br2 are needed to make 10 moles of AlBr3? 10 mol AlBr3 x __________ = 1

  14. Mole Ratios • Definition- ratio between the numbers moles of any 2 substances in a balanced chemical equation. 2Al + 3Br2 2AlBr3 • How many moles of Br2 are needed to make 10 moles of AlBr3? 10 mol AlBr3 x 3 moles Br2 = 1 2 mol AlBr3

  15. Mole Ratios • Definition- ratio between the numbers moles of any 2 substances in a balanced chemical equation. 2Al + 3Br2 2AlBr3 • How many moles of Br2 are needed to make 10 moles of AlBr3? 10 mol AlBr3 x 3 moles Br2 = 15 mol Br2 are needed 1 2 mol AlBr3 Mole to Mole Conversion

  16. Smart Board • Ex: How many moles of chlorine are needed to react with 5 moles of sodium? 2 Na + Cl2 2 NaCl =

  17. Mole Ratios more ex. • Ex: How many moles of chlorine are needed to react with 5 moles of sodium? 2 Na + Cl2 2 NaCl 5 moles Na 1 mol Cl2 2 mol Na = 2.5 moles Cl2

  18. Mole Ratios more ex. =

  19. Do scales measure in moles???

  20. Do scales measure in moles? Nothey measure in grams, therefore convert moles to grams 1 mole C3H8 x 39.06 g C3H8 = 39.06 g C3H8 1 mol C3H8

  21. Types of conversionproblems • Mole to mole • Mole A to mass of B in a reaction • Mass A to mass B

  22. Stoichiometric Calculations The coefficients in the balanced equation give the ratio of moles of reactants and products

  23. Stoichiometric Calculations If you are given a chemical substance in grams convert it to moles Then use a mole ratio to change form one type of mole to another type of mole If needed change moles back to grams

  24. Stoichiometric Calculationshow many moles of water from 1g C6H12O6 C6H12O6 + 6 O2 6 CO2 + 6 H2O Starting with 1.00 g of C6H12O6… we calculate the moles of C6H12O6… use the coefficients to find the moles of H2O… and then turn the moles of water to grams

  25. Stoichiometric Calculations C6H12O6 + 6 O2 6 CO2 + 6 H2O Starting with 1.00 g of C6H12O6… we calculate the moles of C6H12O6… use the coefficients to find the moles of H2O… and then turn the moles of water to grams

  26. Stoichiometric Calculations C6H12O6 + 6 O2 6 CO2 + 6 H2O Starting with 1.00 g of C6H12O6… we calculate the moles of C6H12O6… use the coefficients to find the moles of H2O… and then turn the moles of water to grams

  27. Practice • Write the balanced reaction for hydrogen gas reacting with oxygen gas. 2 H2 + O2 2 H2O • How many moles of reactants are needed? • What if we wanted 4 moles of water? • What if we had 3 moles of oxygen, how much hydrogen would we need to react and how much water would we get? • What if we had 50 moles of hydrogen, how much oxygen would we need and how much water produced?

  28. Mole A/Mole B Mole Ratio

  29. 3 Easy steps for using Dimensional Analysis Step 1- find the given in the problem and put it over 1 Given # with units 1 Step 2- take top units and copy them to bottom of next step Top Units x . Same as Top Units Step 3- Choose correct conversion factor Molar Mass or Mole to Mole Ratio 1 mole ‘same substance’# moles ‘different substance’ g of ‘same substance’ # moles ‘first substance’

  30. Mole A/Mole B Mole Ratio Mole/g or g/mole Molar mass Mole/g or g/mole Molar Mass Given 1 Top Units x . Same as Top Units Choose conversion factor Molar Mass or Mole Ratio

  31. Mole to Mole Conversions How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with sodium metal? 2 Na + Cl2 2 NaCl 2.6 moles Cl2x ____________= NaCl 1

  32. Mole to Mole Conversions How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with sodium metal? 2 Na + Cl2 2 NaCl 2.6 moles Cl2x 2mole NaCl= 5.2 moles NaCl 1 1mole Cl2

  33. Mole-Mass Conversions Ex: • How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? 2 Na + Cl2 2 NaCl 5.00 moles Na 1 = g Cl2

  34. Mole-Mass Conversions Ex: • How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride? 2 Na + Cl2 2 NaCl 5.00 moles Na 1 mol Cl2 70.90g Cl2 1 2 mol Na 1 mol Cl2 = 177g Cl2

  35. Mass-Mole Calculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water 2 C2H6 + 7 O2 4 CO2 + 6 H20 10.0 g H2O 1 = mol C2H6

  36. Mass-Mole Calculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water 2 C2H6 + 7 O2 4 CO2 + 6 H20 10.0 g H2O 1 mol H2O 2 mol C2H6 18.0 g H2O 6 mol H20 = 0.185 mol C2H6

  37. Mass-Mass Conversion Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. N2 + 3 H2  2 NH3 2.00g N2 = 1

  38. Mass-Mass Conversion Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. N2 + 3 H2  2 NH3 2.00g N2 1 mol N2 2 mol NH3 17.04g NH3 = 28.02g N2 1 mol N2 1 mol NH3 = 2.4 g NH3

  39. Limiting Reactants

  40. Limiting Reactants The limiting reactant is the reactant present in the smallest stoichiometric amount HUHHH???????

  41. The limiting reactant is the reactant present in the smallest stoichiometric amount • In other words, it’s the reactant that runs out first Or gets used up first in a chemical reaction

  42. Which Reactant is the Limiting Reactant? • Available Ingredients (reactants) • 4 slices of bread • 1 jar of peanut butter • 1/2 jar of jelly • Limiting Reactant? • Excess Reactants?

  43. Which Reactant is the Limiting Reactant? • Available Ingredients (reactants) • 4 slices of bread • 1 jar of peanut butter • 1/2 jar of jelly • Limiting Reactant • bread • Excess Reactants • peanut butter and jelly

  44. The reactant that runs out first is the limiting reactant • But How do we determine which reactant will be used up first in a chemical reaction?

  45. You need 2 things • Balanced Equation and • The amounts of all reactants 2 H2 + O2 2 H2O Amounts of reactants 10 H2 and 7 O2

More Related