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Chapter 5

Chapter 5. Chemical Reactions. Chemical Reactions: Chemical Equations. Reactants. Products. 2H 2 + O 2  2H 2 O. Chemical Reactions: Equations. Balance the following equations. Equations with Polyatomic Ions. Equations with Polyatomic Ions. Atomic Weights.

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Chapter 5

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  1. Chapter 5 Chemical Reactions

  2. Chemical Reactions: Chemical Equations

  3. Reactants Products 2H2 + O2 2H2O

  4. Chemical Reactions: Equations • Balance the following equations.

  5. Equations with Polyatomic Ions

  6. Equations with Polyatomic Ions

  7. Atomic Weights

  8. Molecular Weight and Formula Weight NaCl

  9. 1Na 22.99 amu NaCl 1Cl + 35.45 amu NaCl 58.44 amu Formula weight is the sum of the atomic masses (in amu) in a formula unit of an ionic compound.

  10. Alternate Example 3.1 Calculating the Formula Weight from a Formula • Calculate the formula weight of the following compounds from their formulas : • calcium hydroxide, Ca(OH)2; • methylamine, CH3NH2.

  11. Molecular Weight and Formula Weight H2O

  12. 1S 32.07 amu 2O + 2 x 16.00 amu SO2 SO2 64.07 amu Molecular mass (or molecular weight) is the sum of the atomic masses (in amu) in a molecule.

  13. http://www.uksafari.com/postcard/mole.htm

  14. http://www.dumville.org/moles/starnosed.html

  15. 1 dozen = 12 items

  16. 6.02 x 1023 somethings = 1

  17. Mass and Moles of a Substance • The Mole Concept 1-octanol (C8H17OH) Mercury(II) Iodide (HgI2) Sulfur (S8) Methanol (CH3OH)

  18. One seat One tricycle Three tires

  19. Amu = grams/mole 6.02 x 1023 somethings = 1mole

  20. Molar Mass

  21. Molar Mass • Molar mass (formula weight) can be used to convert from grams to moles, and from moles to grams

  22. Mass and Moles of a Substance • Mole calculations • Suppose we have 100.0 grams of iron (Fe). The atomic weight of iron is 55.8 g/mol. How many moles of iron does this represent?

  23. Mass and Moles of a Substance • Mole calculations • Conversely, suppose we have 5.75 moles of magnesium (atomic wt. = 24.3 g/mol). What is its mass?

  24. Mass and Moles of a Substance • Mole calculations • This same method applies to compounds. Suppose we have 100.0 grams of H2O. How many moles does this represent?

  25. Alternate Example 3.4 Converting Moles of Substance to Grams A sample of nitric acid contains 0.253 mol HNO3. How many grams is this?

  26. First Alternate Example 3.5 Converting Grams of Substance to Moles Calcite is a mineral composed of calcium carbonate, CaCO3. A sample of calcite composed of pure calcium carbonate weighs 23.6 g. How many moles of calcium carbonate is this?

  27. Mass and Moles of a Substance • Mole calculations • Suppose we have 3.25 moles of glucose, C6H12O6. What is its mass?

  28. Second Alternate Example 3.5 Converting Grams of Substance to Moles The average daily requirement of the essential amino acid leucine, C6H14O2N, is 2.2 g for an adult. How many moles of leucine are required daily? The formula weight for leucine is 132 g/mol.

  29. Grams to Moles • Calculate the number of moles of sodium ions, Na+, in 5.63 g of sodium sulfate, Na2SO4

  30. Do You Understand Molecular Mass? How many moles of H are in 72.5 g of C3H8O ?

  31. Molar Interpretation of a Chemical Equation • The balanced chemical equation can be interpreted in numbers of molecules, but generally chemists interpret equations as “mole-to-mole” relationships.

  32. The balanced chemical equation can be interpreted in numbers of molecules, but generally chemists interpret equations as “mole-to-mole” relationships.

  33. Molar Interpretation of a Chemical Equation • Suppose we wished to determine the number of moles of NH3 we could obtain from 4.8 mol H2. Reaction coefficients FW of A FW of B grams A moles A moles B grams B

  34. Alternate Example 3.13 Relating the Quantity of Reactant to Quantity of Product Propane, C3H8, is normally a gas, but it is sold as a fuel compressed as a liquid in steel cylinders. The gas burns according to the equation C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) How many grams of CO2 are produced when 20.0 g of propane is burned?

  35. Mass Relationships in Chemical Equations • Amounts of substances in a chemical reaction by mass. • How many grams of HCl are required to react with 5.00 grams manganese dioxide according to this equation? Reaction coefficients MW of A MW of B grams A moles A moles B grams B

  36. Limiting Reagent • The limiting reactant (or limiting reagent) is the reactant that is entirely consumed when the reaction goes to completion. • The limiting reagent ultimately determines how much product can be obtained.

  37. Limiting Reagent • Zinc metal reacts with hydrochloric acid by the following reaction. • If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H2 are produced?

  38. Urea, (NH2)2CO, is prepared by reacting ammonia with carbon dioxide: 2NH3 + CO2 (NH2)2CO + H2O In one process, 637.2 g of NH3 are treated with 1142 g of CO2. Which of the two reactants is the limiting reagent? Calculate the mass of (NH2)2CO formed. The formula weight of Urea is 60.06 g/mol.

  39. The theoreticalyield of product is the maximum amount of product that can be obtained from given amounts of reactants.

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