1. Exam Review #2b

2. Introduction to Stoichiometry What is Mole Ratio? How can I determine mole ratio from balanced equation?

3. What is Mole Ratio? Balanced equations reveal molar ratios Moles = Coefficients

4. Balance the following equation: _____ N 2 (g) + _____H 2 (g)  ______ NH 3 (g) 2 3 1 N 2 to H 2 _______________________________ N 2 / NH 3 _______________________________ H 2 / NH 3 _______________________________ Write the mole ratio for the following: 1:3 1:2 3:2

5. Importance of Molar Ratios Molar ratios help to connect amounts of reactants. ? Mole (of substance A) ? Mole (of substance B)

6. Apply to the Balanced Equation How many moles of Ammonia could I make from 3 moles of Nitrogen? _____ N 2 (g) + _____H 2 (g)  ______ NH 3 (g) 1 3 2 Given: 3 mol N 2 mol N 2 mol NH 3 1 2 6 mol NH 3 =

7. Converting Mass to Mass Problems Use Road Map Provided Follow Directions – like following a recipe!

8. Example #1: What mass of carbon is required to react with oxygen to produce 12g of CO? _____ C + ______ O 2  ______ CO 2 12 Circle the known. Box what you are trying to find. 12 g CO g CO mol CO C: 1 x 12 = 12 O: 1 x 16 = 16 + 28 g/ mol 28 1 mol CO mol C 2 2 g C C: 1 x 12 = 12 g/ mol 1 12 = 5.14 g C

9. Example #1 _____ N 2 (g) + _____H 2 (g)  ______ NH 3 (g) 132 Given:25g N 2 g N 2 mol NH 3 1 28 40.0L NH 3 = Mass to Volume mol N 2 1 1 3 mol NH 3 L NH 3 22.4 What volume of NH 3 at STP is produced if 25g of N 2 is reacted with an excess of H 2 ?

10. What is a limiting reactant? Reactant in a chemical reaction that limits the amount of product that can be formed The reaction will stop once it all is consumed. Label the Limiting Reactant on the diagram in your notes

11. Real world Example: What is the Limiting Reactant? Limiting Reactant = Brownie Mix

12. Chemistry Example: What is the Limiting Reactant? Limiting reactant = H 2

13. What is an excess reactant? Reactant in a chemical reaction that remains when a reaction stops Remains because there is nothing to react with it Label the Excess Reactant on the diagram in your notes

14. Real world Example: What is the Excess Reactant? Excess Reactants = Buns, cheese, tomato

15. Chemistry Example: What is the Excess Reactant? Green structures are the excess reactant

16. Theoretical Yield Maximum amount of product that could be formed from a given amount of reactants

17. Actual Yield Amount of product actually formed when a reaction is carried out This information is found in the experiment

18. Percent Yield: Formula

19. Why don’t reactions go to completion? 1. The reactants are not pure.

20. Why don’t reactions go to completion? 2. Loss of product in filtration

21. Why don’t reactions go to completion? 3. Competing reactions

22. Why don’t reactions go to completion? 4. Measuring errors

23. Example What is the theoretical yield of CaO if 24.8 g of CaCO 3 is heated? _____ CaCO 3  _____ CaO + ______ CO 2 24. 8 g CaCO 3 x ________ x _________ x ________ = 13.9 g CaO Theoretical Yield = 13.9 g CaO 100.1 g CaCO 3 1 mol CaCO 3 1 mol CaO 56 g CaO

24. Solutions Parts of a Solution Molarity, Molality, Mole Fraction, Dilution

25. Solution Homogenous mixture of two or more substances in a single phase

26. Parts of a solution Solvent: The dissolving medium

27. Parts of a Solution Solute: Disolvee; what is being dissolved Aqueous: Able to be dissolved

28. SolutionSolution: A mixture of two or more substances; both are completely dissolvedcompletely dissolved

29. What is Molarity (M)? Moles of solute per volume of solution

30. Molarity Formula Equation is on the Reference Table

31. Example If you dissolve 20.0 g of NaOH in 250.0 mL of water, what is the molarity of the solution? 20.0 g NaOH 40.0 g NaOH 1 mol NaOH = 0.50 mol NaOH 0.25 L =2.00 mol/L Molarity 250.0 mL = ________ L 0.250

32. What is Molality (m)? Moles of solute per mass of solvent

33. Molality Formula Equation is NOT the Reference Table

34. Example If you dissolve 350.0 g of K 2 Cr 4 in 2.5 kg of water, what is the molality of the solution? 350 g K 2 Cr 4 288 g K 2 Cr 4 1 mol K 2 Cr 4 = 1.22 mol K 2 Cr 4 2.5 kg =0.49 mol/kg Molality

35. Molarity and Molality Summary Table MolarityMolality Symbol Equation Units Mm Mol of solute Liters of solution Mol of solute Kilogram of solution mol L mol kg

36. Mole Fraction (  ) Ratio of the number of moles of a solute to the total number of moles in a solution What is the ratio of yellow fish to the total number of fish? 2929 2:9

37. Mole Fraction Equation

38. Example 1.20 g C 2 H 5 OH 50 g C 2 H 5 OH 1 mol C 2 H 5 OH = 0.024 mol C 2 H 5 OH (0.024 mol C 2 H 5 OH + 0.93 mol H 2 O) = 0.025 mol Calculate the mole fraction of ethanol, C 2 H 5 OH, in a solution prepared by dissolving 1.20 g of ethanol in 16.8 g of water. 16.8 g H 2 O 18 g H 2 O 1 mol H 2 O = 0.93 mol H 2 O

39. ConcentratedDilute Large amount of solute in a solution Small amount of solute in a solution Dilute Concentrated

40. Three conditions of solution equilibrium Unsaturated: contains LESS solute than a saturated solution

41. Three conditions of solution equilibrium Saturated: contains the MAXIUMUM amount of dissolved solute at specified temp

42. Three conditions of solution equilibrium Super saturated: contains MORE dissolved solute than a saturated solution

43. Dilution The process of reducing the concentration of a solute in solution by adding more solvent

44. Dilution Equation M = Molarity and V = Volume

45. Example To what volume must 1.0 L of a 6.0 M solution of HCl be diluted in order to prepare a 0.2 M solution? M 1 V 1 = M 2 V 2 M 1 = 6.0 M V 1 = 1.0 L M 2 = 0.2 M V 2 = ? (0.1 L)(6.0 M) = (0.2 M)(V 2 ) V 2 = 30 L

46. Solubility depends…. 1.Nature of the solute and solvent 2.Temperature: Must be specified 3.Pressure (for gases): Must be specified

47. Solubility Curves A graph showing the relationship between solubility and temperature. Line represents saturated solution. Above line - supersaturated; Below the line - unsaturated

49. Acids and Bases Properties Theories of Behavior

50. Properties of Acids Tart/Sour Taste

51. Properties of Acids Reactive with metals -Video clip 1:29 Reaction between nitric acid and copper

52. Properties of Acids Conducts electricity

53. Properties of Acids Strong electrolytes -Electrolyte: Conducting medium in which the flow of current is accompanied by the movement of matter in the form of ions

54. Properties of Acids Neutralize bases producing a salt and water

55. Properties of Acids Turns blue litmus paper to red

56. Properties of Bases Bitter Taste

57. Properties of Bases Slippery Feel

58. Properties of Bases Neutralize acids producing a salt and water

59. Properties of Bases Weak electrolytes -Electrolyte: Conducting medium in which the flow of current is accompanied by the movement of matter in the form of ions

60. Properties of Bases Turns red litmus paper to blue

61. Arrhenius Theory ACIDS: Substances which produce hydrogen ions (H+) in solution. HCl  H + + Cl Ion: an atom or a group of atoms that has gained or lost one or more electrons and has become electrically charge. Proton (H + ) donor Hydrogen (H + ) donor

62. Common Acids HCl = Hydrochloric acid HNO 3 = Nitric acid H 2 SO 4 = Sulfuric acid

63. Arrhenius Theory BASES: Substances which produce hydroxide ions (OH-) in solution. NaOH  Na + OH - Hydroxide (OH - ) donor

64. Common Bases NaOH = Sodium hydroxide KOH = Potassium hydroxide NH 3 = Ammonia

65. Bronsted-Lowry Theory: 1923 ACID: proton donor, H + donor BASE: proton acceptor, H + acceptor Broadened categories of acids-bases

66. Key Terms: ACID A substance that produces protons, H +

67. Key Terms: BASE A substance that produces hydroxide ions, OH -

68. Key Terms: CONJUGATE ACID Substance formed as base gains H+ ion (proton) Conjugate Acid

69. Key Terms: CONJUGATE BASE Conjugate Base Substance remains after acid donates H+ ion

70. Example #1 NH 3 + HCl  NH 4 + + Cl - Base Conjugate Acid Conjugate Base http://www.lakelandschools.us/lh/lburris/pages/acid-base.htm

71. pH scale 114 768 Acid Base (Alkaline) Neutral

72. Logarithmic Scale A ten-fold difference between each successive full number on the scale

73. Logarithmic Scale – ACID Each whole pH value BELOW 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6.

74. Logarithmic Scale: BASE Each whole pH values ABOVE 7 is ten times more basic than the next lower whole value. For example, pH 10 is ten times more alkaline than pH 9 and 100 times (10 times 10) more alkaline than pH 8.

75. Basic Equations (Reference Table) pH = -log[H + ] pOH = -log[OH - ] pH + pOH = 14 [H+] = 10 -pH [OH-] = 10 -pOH

76. Strength of Acids and Bases depend on … -How much acid/base ionizes in water -Refers to how many H+ and OH- actually dissociate in water

77. Strong Acids Completely ionize in water Examples: Hydrochloric Acid (HCl) and Sulfuric acid (H 2 SO 4)

78. Weak Acid SLIGHTLY ionize in water Example: Acetic Acid (vinegar) = HC 2 H 3 O 2

79. Strong Bases Dissociate into metal ions and hydroxide ions Examples: Sodium hydroxide (NaOH), Calcium hydroxide (Ca(OH) 2 )

80. Weak Bases React with water to form hydroxide and conjugate Example: Ammonia (NH 3)

81. What is a Salt? Ionic compounds produced in the reaction of a acid and a base.

82. Naming Bases Name of the first element plus hydroxide except Ammonia (NH 3 ) and Ammonium Sodium Hydroxide - NaOH Potassium Hydroxide - KOH Ammonium Hydroxide - NH 4 OH Calcium Hydroxide - Ca(OH) 2 Magnesium Hydroxide - Mg(OH) 2 Barium Hydroxide - Ba(OH) 2 Aluminum Hydroxide - Al(OH) 3 Lithium Hydroxide - LiOH

83. Naming Acids with simple Anions 1.The first part of the name uses the prefix Hydro- 2. This is followed by a the name of the simple anion, which is shortened and - ic added – Example: Chlorine (Cl-) would become chloric 3. The last part of the name is the word acid Example: HCl = Hydrochloric acid

84. Examples Hydrofluoric Acid – HF Hydrobromic Acid - HBr Hydroiodic Acid - HI Hydrosulfuric Acid - H 2 S

85. Naming Acids with Polyatomic Ions 1.The first part of the name is the name of the anion SHORTENED. 3. The last part of the name is the word acid Example: HNO 3 NO 3 = Nitrate Nitric Acid 2. One of two suffixes added to this name. Use -ic if the anion name ends in – ate Use -ous if the anion name ends in – ite

86. Writing Acid Formulas Determine the anion present from the name. – Since the compound is an acid the cation (positive ion) is H + – Write down the formulas of the two ions. Make the value of the charge on the negative ion the subscript on the hydrogen ion Example: Sulfuric Acid Sulfuric ------> Sulfate --------> SO 4 2- Acid -------> Hydrogen --------> H +1 Put together and Criss cross Formula ---> H 2 SO 4

87. Examples Nitric Acid - HNO 3 Nitrous Acid - HNO 2 Sulfuric Acid - H 2 SO 4 Sulfurous Acid - H 2 SO 3 Phosphoric Acid - H 3 PO 4 Phosphorous Acid - H 3 PO 3

88. Neutralization Reaction The process that occurs when an acid and a base come in contact with each other to make a salt and water

89. What is a Titration? Lab method used to figure out the concentration of a reactant or reagent

90. Acid-Base Titration A solution containing a known concentration of base is slowly added to an acid until the acid is completely neutralized or vice versa

91. Titration Apparatus Known solution is in the Biuret (Titrant) Unknown and the Indicator

92. Indicator A substance that indicates the degree of acidity or basicity of a solution through color changes Phenolphthalein turns pink in base at 8 pH

93. How to do a Titration

94. Graphical Representations Titrations are represented graphically with end points [pH=7], and equivalence points [H+] = [OH-]. Steepest part of the curve where the pH rises the fastest

95. Compare the graphs of strong acids/bases with the graphs of weak acids/bases

96. Titration Formula M A V A = M B V B M A = Molarity of Acid V A = Volume of Acid M B = Molarity of Base V B = Volume of Base

97. Example #1 A student neutralizes a 15 mL sample of vinegar (acetic acid) with 31.85 mL of a 0.4 M NaOH solution. What is the molarity of the vinegar? M A = x V A = 15 mL M B = 0.4 M V B = 31.85 mL (x)(15 mL) = (0.4 M)(31.85 mL) 0.85 M of vinegar