1. Chapter 5 A Matter of Concentration

2. Ionic Phenomena = Things that happen to ions, which can be observed

3. What is matter? STUFF! http://www.youtube.com/watch?v=tBQcpF_j5Xg

4. Matter can be found in 3 states:

5. http://www.youtube.com/watch?v=HAPc6JH85pM

6. Matter can be categorized 5 ways!

7. Matter Element Compound Pure substancesMixtures Homogeneous mixtures Suspensions Heterogeneous mixtures

8. Element Substances on the periodic table Made up of identical atoms 100% copper wire (Cu)Pure gold (Au)

9. More elements Chlorine gas (Cl 2 )

10. Compound A substance which contains different atoms Water (H 2 O)

11. Sugar (C 12 H 22 O 11 ) Salt (NaCl)

12. Mixtures Contain two or more different elements or compounds, physically mixed together

13. Homogenous Mixtures To the naked eye, looks like one substance (completely uniform) Salt water – looks clear like pure water

14. Vinegar is a mixture of acetic acid (CH 3 COOH) and water (H 2 O) Brass – looks like a pure metal, but it’s a mixture of copper and zinc Solution = Liquid homogenous mixture

15. Sterling silver – mixture of silver and copper Plumber’s solder – mixture of lead and tin

16. Stainless steel – mixture of iron, carbon, chromium, and nickel Air!

17. Heterogeneous Mixtures To the naked eye, it looks like it’s made of two or more substances – an obvious mixture These substances can be taken apart into their original components

18. Asphalt Dirt Concrete

19. The dreaded fruitcake!

20. Suspensions Between homogenous and heterogenous mixtures – tiny solid bits floating around in liquid Murky water

21. Tomato juice – miniscule tomato particles floating in water Strawberry milkshake

22. And now, onto Solutions

23. Milk is a suspension The percentage (1%, 2%, 3.25%) means that it contains that much milk fat, and the rest is water

24. Most of the milk is made of water Water = solvent (what the milk fat is dissolved into) Milk fat = solute (particles dissolved into solvent) Milk in carton = solution (total volume = solvent + solute)

25. Most of the milk is made of water Highest percentage = Highest concentration of milk fat

26. Most of the milk is made of water The higher the percentage of milk fat (solute), the less water is needed as a solvent

27. Most of the milk is made of water In 1L of 1% milk: 10ml milk fat, 990ml water In 1L of 2% milk: 20ml milk fat, 980ml water In 1L of 3.25% milk: 32.5ml milk fat, 967.5ml water

28. Concentration Concentration of milk = amount of milk fat amount of milk

29. Concentration Concentration of milk = amount of milk fat amount of milk

30. Concentration equation Concentration (c) = Solute mass (m) solution volume (V) C = m V C  g/L m  g V  L

31. Making salt water If you add 1g of NaCl to 1 L of water, you get: C = 1 g = 1 g/L 1 L 1 g/L aqueous solution of NaCl

32. Making salt water If you add 10g of NaCl to 1 L of water, you get: C = 10 g = 10 g/L 1 L 10 g/L aqueous solution of NaCl

33. Making salt water If you add 10g of NaCl to 500 mL of water, you get: C = 10 g = 20 g/L 0.5 L 20 g/L aqueous solution of NaCl Remember: 1000ml = 1L

34. Arrange these solutions from lowest to highest concentration Solution# grams of sugar # Litres of solution Concentration (g/L) A3 g1 L B5 g0.5 L C8 g4 L D7 g3 L

35. Arrange these solutions from lowest to highest concentration Solution# grams of sugar # Litres of solution Concentration (g/L) A3 g1 L3 g/L B5 g0.5 L10 g/L C8 g4 L2 g/L D7 g3 L2.3 g/L Solution C  Solution D  Solution A  Solution B

36. Which salt solution is most concentrated? Solution# grams of salt # Litres of solution Concentration (g/L) A10 g400 ml B0.5 kg1.5 L C0.2 kg800 ml

37. Which salt solution is most concentrated? Solution# grams of salt # Litres of solution Concentration (g/L) A10 g400 ml25g/L B0.5 kg1.5 L333.3g/L C0.2 kg800 ml250g/L C = m ÷ V = 10g ÷ 0.4L = 25g/L C = m ÷ V = 0.5kg ÷ 1.5L = 500g ÷ 1.5L = 333.3g/L C = m ÷ V = 0.2kg ÷ 0.8L = 200g ÷ 0.8L = 250g/L

38. Different ways to say numbers of stuff 12 eggs = 1 dozen eggs A score of years = 20 years Avogadro’s number = 602, 000, 000, 000, 000, 000, 000, 000 = 6.02 x 10 23 molecules = One mole

39. Mole! Quick lesson on the mole and Avogadro’s number: http://www.youtube.com/watch?v=TEl4jeETVm g

40. Molar mass An element’s atomic mass (in grams) has one mole of that element’s atoms Atomic mass of Fluorine = 18.998 U Molar mass of Fluorine = 18.998g (round to 19g) = 1 mole of Fluorine atoms Symbol for mole = mol

41. Molar mass An molecule’s atomic mass (in grams) has one mole of that molecule’s atoms Atomic mass of water (H 2 0) = (2 x 1.008) + 15.999 = 18.015 U Molar mass of H 2 0 = 18.015 g (round to 18 g) = 1 mole of water molecules

42. The Mole equation Number of moles (n) = mass of solute (m) Molar mass (mm) n = m mm n  mol m  g mm  g (per mol)

43. How many moles of atoms are in 444g of radon (Rn)?

44. Step 1. Find the atomic mass of Radon Rn 86 Radon 222.018 Atomic mass = 222.018 U

45. Step 2. Make the atomic mass into grams per mole (molar mass) of Rn Rn 86 Radon 222.018 Molar mass = 222.018 g  222 g

46. Step 3. Find out the number of moles using the mole equation Mass (m) = 444 g Molar mass (mm) = 222.018 g  222 g mm n = m 222 g/mol n = 444 g n = 2 moles of radon

47. How many moles are in 591g of gold (Au)?

48. Step 1. Find the atomic mass of Gold Au 79 Gold 196.967 Atomic mass = 196.967 U 2.4

49. Step 2. Make the atomic mass into grams per mole (molar mass) of Au Au 79 Gold 196.967 Molar mass = 196.967 g  197 g 2.4

50. Step 3. Find out the number of moles using the mole equation Mass (m) = 571 g Molar mass (mm) = 196.967 g  197 g mm n = m 197 g/mol n = 571 g n = 3 moles of gold

51. Steps to find the number of moles of an element/compound Step 1. Find the atomic mass of the element/compound Step 2. Make the atomic mass into grams per mole (molar mass) Step 3. Find out how many moles are in the given weight of the element/compound using the mole equation

52. These calculations also work with compounds!

53. How many moles are in 16.3 g of magnesium bromide (MgBr 2 )?

54. Step 1. Find the atomic mass of MgBr 2 Mg 12 Magnesium 24.305 Atomic mass = 24.305 + 2(79.904) = 184.113 U Br 35 Bromine 79.904 1.22.8

55. Step 2. Make the atomic mass into grams per mole (molar mass) of MgBr 2 Mg 12 Magnesium 24.305 Molar mass = 184.113 g  184.1 g Br 35 Bromine 79.904 1.22.8

56. Step 3. Find out the number of moles using the mole equation Mass (m) = 16.3g Molar mass (mm) = 184.113 g  184.1 g mm n = m 184.1 g/mol n = 16.3 g n = 0.089 moles of MgBr 2

57. Molar concentration (Molarity) Molar concentration (C) = # moles of solute (n) volume of solution (V) C = n V C  mol/L n  mol V  L

58. A solution of 800ml contains 2 moles of NaCl. What is the molar concentration of the solution?

59. There is only one step: Calculate M! V C = n = 2 mol = 2.5 mol/L = 2.5 M 0.800L

60. A chemist wants to prepare a 1.25M aqueous solution of Ca(NO 3 ) 2. She has 82g of calcium nitrate. Calculate the maximum volume that the chemist can prepare.

61. Molarity = Molar concentration Compound: Can use to get molar mass Mass of soluteWhat we’re looking for: Volume (L)

62. Step 1. Write down what you have, and what you want We have: C = 1.25 M = 1.25 mol/L mass of solute = 82 g solute = Ca(NO 3 ) 2 We want: Volume of solution (L) = ?

63. Step 2. Find the molar mass of Ca(NO 3 ) 2 N 7 Nitrogen 14.007 Molar mass = 40.078 + 2(14) + 6(16) = 164.086 g  164.1 g/mol O 8 Oxygen 15.999 3.03.5 Ca 20 Calcium 40.078 1.0 CaN 2 O 6

64. Step 3. Find out the number of moles using the mole equation Mass (m) = 82 g Molar mass (mm) = 164.086 g  164.1 g mm n = m 164.1 g/mol n = 82 g n = 0.5 moles of Ca(NO 3 ) 2

65. Step 4. Plug in values to calculate the volume of the solution V C = n

66. Step 4. Plug in values to calculate the volume of the solution V C = n V 1.25 mol/L = 0.50 mol

67. Step 4. Plug in values to calculate the volume of the solution V C = n V 1.25 mol/L = 0.50 mol cross-multiply

68. Step 4. Plug in values to calculate the volume of the solution V C = n V 1.25 mol/L = 0.50 mol cross-multiply 1.25 mol/L (V) = 0.50 mol

69. Step 4. Plug in values to calculate the volume of the solution V C = n V 1.25 mol/L = 0.50 mol cross-multiply 1.25 mol/L (V) = 0.50 mol 1.25 mol/L

70. Step 4. Plug in values to calculate the volume of the solution V C = n V 1.25 mol/L = 0.50 mol cross-multiply 1.25 mol/L (V) = 0.50 mol 1.25 mol/L V = 0.40 L

71. How to solve Molarity problems Step 1. Write down what you have, and what you want Step 2. Find the molar mass of the element/compound Step 3. Find out the number of moles using the mole equation Step 4. Plug values into the molarity equation

72. What if you need another concentration than what you have? They have to dilute it themselves

73. This also saves $$ – chemicals are expensive! They mostly buy the really concentrated ones

74. Back to the milk example In 1L of 1% milk: 10ml milk fat, 990ml water In 1L of 2% milk: 20ml milk fat, 980ml water In 1L of 3.25% milk: 32.5ml milk fat, 967.5ml water

75. If you really wanted to, you could buy 3.25% milk and add water until it had a concentration of 1% If only you knew the dilution equation...

76. Dilution equation Higher Concentration sol’n (C 1 ) x Its Volume (V 1 ) Lower Concentration sol’n (C 2 ) x Its Volume (V 2 ) C 1 V 1 = C 2 V 2 C 1, C 2  mol/L V 1, V 2  L = sol’n = solution

77. Using a stock solution of 17.5 mol/L, you want to prepare 500 ml of a 1.00 mol/L acetic acid solution (CH 3 COOH). What volume of stock solution will you need?

78. Higher concentration solution (C 1 ) Higher concentration sol’n = stock solution Lower concentration solution (C 2 ) What we’re looking for: V 1 = Volume of C 1 Solute V 2 = Volume of C 2

79. Step 1. Write down what you have, and what you want We have: C 1 = 17.5 mol/L V 2 = 500 ml = 0.5 L C 2 = 1.00 mol/L solute = CH 3 COOH We want: V 1 = ?

80. Step 2. Plug values into dilution equation C 1 V 1 = C 2 V 2

81. Step 2. Plug values into dilution equation C 1 V 1 = C 2 V 2 (17.5 mol/L) (V 1 ) = (1.00 mol/L) (0.5 L)

82. Step 2. Plug values into dilution equation C 1 V 1 = C 2 V 2 (17.5 mol/L) (V 1 ) = (1.00 mol/L) (0.5 L) 17.5 (V 1 ) = 0.5

83. Step 2. Plug values into dilution equation C 1 V 1 = C 2 V 2 (17.5 mol/L) (V 1 ) = (1.00 mol/L) (0.5 L) 17.5 (V 1 ) = 0.5 17.5

84. Step 2. Plug values into dilution equation C 1 V 1 = C 2 V 2 (17.5 mol/L) (V 1 ) = (1.00 mol/L) (0.5 L) 17.5 (V 1 ) = 0.5 17.5 V 1 = 0.0286 L = 28.6 mL

85. Steps to solving a dilution problem Step 1. Write down what you have, and what you want Step 2. Plug values into dilution equation

86. pH scale Used to test the strength of an acid or base (Back to the)

87. Acid: pH less than 7 Neutral: pH exactly 7 Base: pH more than 7

88. The pH of various substances SubstancepH (approximate) Sulphuric acid (H 2 SO 4 )0 Hydrochloric acid (HCl), 0.1 M1.0 Vinegar (CH 3 COOH)2.2 Soft drinks, wine, beer3.0 Apples3.1 Black coffee5.0 Soap10.0 Household ammonia11.1 Depilatory cream12.0 Sodium hydroxide (NaOH), 0.1 M13.0

89. The pH of various substances SubstancepH (approximate) Sulphuric acid (H 2 SO 4 )0 Hydrochloric acid (HCl), 0.1 M1.0 Vinegar (CH 3 COOH)2.2 Soft drinks, wine, beer3.0 Apples3.1 Black coffee5.0 Soap10.0 Household ammonia11.1 Depilatory cream12.0 Sodium hydroxide (NaOH), 0.1 M13.0

90. How can HCl be only twice as acidic than vinegar? The way pH is calculated is not linear

91. pH Scale – How it works The pH scale works by powers of 10. That means that an acid with pH 1 has 10 times more H + ions than pH 2. (10 times stronger acid) The left side shows how many times more H + one pH has compared to another.

92. What does pH actually mean? What does it measure? pH = potential of Hydrogen = H + ion concentration of a solution (M or mol/L)

93. H + ion concentration (M)Exponential notation (M)pH 1.01 x 10 0 0 0.11 x 10 -1 1 0.011 x 10 -2 2 0.0011 x 10 -3 3 0.00011 x 10 -4 4 0.000011 x 10 -5 5 0.0000011 x 10 -6 6 0.00000011 x 10 -7 7 0.000000011 x 10 -8 8 0.0000000011 x 10 -9 9 0.00000000011 x 10 -10 10 0.000000000011 x 10 -11 11 0.0000000000011 x 10 -12 12 0.00000000000011 x 10 -13 13 0.000000000000011 x 10 -14 14

94. So if the pH of a solution is 2, it has an H + concentration of 1 x 10 -2 mol/L = 0.01 mol/L

95. How do chemists find the actual pH of a solution? Litmus paper is not that accurate It just tells you if it’s an acid or a base

96. Acid-base indicators Different substances change colour at a precise pH Used together, they can give the approximate pH of a substance

97. bromophenol blue methyl red universal resazurin bromocresol purple phenolphthalein Turning point = when the indicator changes colour

98. Turning Point – Methyl Red Let’s see what happens when we use Methyl Red. MR is a liquid. If we put a few drops into each beaker, we’ll see what happens. pH 0 pH 1 pH 2 pH 3 pH 4 pH 5 pH 6 pH 8 pH 9 pH 10 pH 11 pH 12 pH 13 pH 14 pH 7

99. Turning Point – Methyl Red So what is the turning point of Methyl Red? pH 0 pH 1 pH 2 pH 3 pH 4 pH 5 pH 6 pH 8 pH 9 pH 10 pH 11 pH 12 pH 13 pH 14 pH 7

100. Turning Point – phenolphthalein Let’s see what happens when we use phenolphthalein If we put a few drops into each beaker, we’ll see what happens. pH 0 pH 1 pH 2 pH 3 pH 4 pH 5 pH 6 pH 8 pH 9 pH 10 pH 11 pH 12 pH 13 pH 14 pH 7

101. Turning Point – phenolphthalein So what is the turning point of phenolphthalein? pH 0 pH 1 pH 2 pH 3 pH 4 pH 5 pH 6 pH 8 pH 9 pH 10 pH 11 pH 12 pH 13 pH 14 pH 7

102. pH paper = Universal indicator Here, the universal indicator paper is dipped in the solution and compared to the colours

103. What is the pH range of this solution? IndicatorColour changeTurning point Phenol redyellow  red6.4 – 8.2 Bromophenol blueyellow  violet3.0 – 4.6 Indigo carmineblue  yellow12.0 – 14.0 Bromothymol blueyellow  blue6.0 – 7.6 This solution is yellow in phenol red, violet in bromophenol blue, blue in indigo carmine and yellow in bromothymol blue

104. What is the pH range of this solution? IndicatorColour changeTurning point Phenol redyellow  red6.4 – 8.2 Bromophenol blueyellow  violet3.0 – 4.6 Indigo carmineblue  yellow12.0 – 14.0 Bromothymol blueyellow  blue6.0 – 7.6 This solution is yellow in phenol red (pH < 6.4) violet in bromophenol blue (pH > 4.6) blue in indigo carmine (pH < 12.0) and yellow in bromothymol blue (pH < 6.0) pH of solution: 4.6 – 6.0