VWT 272 Class 7. Quiz 5. Number of quizzes taken 26 Min 12 Max 30 Mean 26.9 Median 28 Mode 30

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1 VWT 272 Class 7 Quiz 5 Number of quizzes taken 26 Min 12 Max 30 Mean 26.9 Median 28 Mode 30

2 Week 7 Concentration, The Mole, Density, Brix and its Kin When you can measure what you are speaking about, and express it in numbers, you know something about it... William Thompson, 1st Baron Kelvin ( )

3 Plan of Study The Mole Concentration Molarity Density Brix

4 The Mole

5 Counting Units A pair = 2 objects A dozen = 12 objects A gross = 144 objects A Ream = 500 objects The Mole The Chemists Dozen A Mole = x objects

6 The Mole The Chemists Dozen Counting Units do not imply size A pair of stereo speakers is larger than a dozen eggs >

7 The Mole The Chemists Dozen Counting units do not imply weight A gross of Finding Dory Caps weigh more than a ream paper

8 The Mole The Chemists Dozen A mole of something is 6.02 x objects A mole of marshmallows would cover the earth to a depth of 19 Km A mole of moles (the animal) would have a mass of more than ½ of the moon A mole of sand would fill a cube 4.4 Km (2.7 mi) on a side

9 The Mole The Chemists Dozen A mole of something is 6.02 x objects

10 Molecular Mass The Weight (in AMU) of a Molecule The sum of the weight of its component atoms AMU [u] = kg Get Atomic Mass from the Periodic Table

11 Molecular Mass Example NaCl u u = u u x kg/u = kg/molecule kg/molecule

12 Molecular Mass Example Tartaric Acid (C 4 H ) (4 x u) + (6 x 1.008u) + (6 x u) = u u x kg/u = kg kg/molecule

13 Molar Mass Gold The mass of one mole of each of the atoms in a compound Expressed in units of g/mol X atoms of gold (Au) weigh g Au has a Molar Mass of g/mol

14 Molar Mass Hydrogen Atom The mass of one mole of each of the atoms in a compound Expressed in units of g/mol X atoms of hydrogen (H) weigh 1.008g H has a Molar Mass of 1.008g/mol

15 Molar Mass Hydrogen Molecule (H 2 ) The mass of one mole of each of the atoms in a compound Expressed in units of g/mol X atoms of hydrogen (H) weigh 1.008g 2 atoms of H per molecule of H 2 H 2 has a Molar Mass of 1.008g/mol g/mol = g/mol

16 Examples Water (H 2 O) Molar Mass (1.008 x 2) = g/mole Copper Sulfate (CuSO 4 ) (4 x 16.00) = g/mole Linalool (C 10 H 18 O) g/mole

17 Molar Mass of LARGE molecules Examples Tannic Acid (C 76 H 52 O 46 ) g/mole Raspberry ellagitannin (C 116 H 76 O 74 ) g/mole

18 Concentration The amount of a substance of interest (solute) contained per unit of volume (of solvent) Solute The substance dissolved in a solution Solvent The substance that dissolves the solute to form a solution

19 Concentration Moose in Maine? The amount of a substance of interest (solute) contained per unit of volume (of solvent) Solute = Moose Solvent = the State of Maine (and 1 mile above it) 75,000 Moose in the State of Maine Maine (+ Atmosphere) = 35,385 mi 3 75,000 moose/35,385 mi 3 = 2.1 moose/mi 3 Unit Volume in this example = mi 3

20 Concentration Bugs in Peanut Butter? The amount of a substance of interest (solute) contained per unit of volume (of solvent) Solute = Insect Fragments Solvent = peanut butter 136 insect fragments per 16 oz jar of peanut butter FDA allows 287 insect fragments/l of peanut butter Unit Volume in this example = Liter

21 Concentration Oxygen in Air? The amount of a substance of interest (solute) contained per unit of volume (of solvent) Solute = Oxygen Gas (O 2 ) Solvent = Air Dry air is 20.95% O 2 Unit Volume (implied) = 100 units or ml O 2 /L Unit Volume = 1 L

22 Concentration Dilute vs. Concentrated Generalized terms that refer to the amount of solute in a given amount of solvent

23 Concentration Concentrated vs. Saturated Saturated Solution holds as much solute in solution as possible at a given temperature Solute 0 C 20 C 40 C 60 C 80 C Sucrose C 12 H 22 O Sodium Cloride NaCl g solute/100.0 ml H 2 O

24 Saturated Solution Concentration Concentrated vs. Saturated holds as much solute in solution as possible at a given temperature Concentration curve for solids into liquids

25 Concentration Supersaturated Supersaturated Solution holds more solute in solution than can be dissolved at a given temperature

26 Concentration Supersaturated Supersaturated Solution holds more solute in solution than can be dissolved at a given (cooler) temperature solute wants to come out of solution Agitation Condensation nuclei seed crystal

27 Concentration Supersaturated - Sodium Acetate Supersaturated Solution holds more solute in solution than can be dissolved at a given temperature Sodium Acetate C 2 H 3 NaO 2 or CH 3 COONa

28 Concentration Supersaturated - Sodium Acetate

29 Concentration Supersaturated - Sodium Acetate

30 Concentration The Special Case of Gasses Gasses have backwards solubility curves You can dissolve more gas (solute) in a cold solvent than in a warm solvent

31 Concentration Supersaturated with Gas Supersaturated Solution holds more solute in solution than can be dissolved at a given (warmer) temperature solute wants to come out of solution Agitation Condensation nuclei seed crystal scratch on glass

32 Concentration Supersaturated with Gas

33 Cold Wine Concentration Gas Implications for Wine Oxygen more likely to dissolve and stay in solution in cold wine Cold Stability

34 Sparkling Wine Concentration Gas Implications for Wine Disgorge at a lower temperature = less loss of CO 2 bubbles Difficulty in measuring bubble rate No standard glass Cellulose fibers from towel

35 Concentration: Molarity Molarity [M] A measure of the concentration of something in a solution The unit for molar concentration used in chemistry is mol/l If you have 1 mole of something dissolved in 1 L of solute the concentration is 1 mol/l A solution of concentration 1 mol/l is also denoted as 1 molar (1 M) If you have 4.2 mole of something dissolved in 1 L of solute the concentration is 4.2 mol/l A solution of concentration 4.2 mol/l is also denoted as 4.2 molar (4.2 M)

36 Molarity Examples 0.80 moles of Acetic Acid (C 2 H 4 O 2 ) in L of water 0.80 M commercial vinegar Sea Water contains about 28.0 g of NaCl per L Molar Mass of NaCl is g/mole 28.0 g x 1 mole/58.44 g = mole = 0.479M

37 Molarity More Examples Sea Water contains from 0 to 20 mg/l oxygen (O 2 ) Molecular mass of O 2 is 32.0 g 6.2x10-4 M 2 cubes of sucrose (C 12 H 22 O 11 ) in a mug of tea 1 cube = 4 g 1 mug = 350 ml M

38 Molarity Yet more Examples g CuSO 4 dissolved in L water g CuSO 4 dissolved in L water g CuSO 4 dissolved in L water g CuSO 4 dissolved in L water

39 Molarity Water can be BOTH a Bronsted-Lowry Acid or a Bronsted-Lowry Base at the same time Concentration of H 3 O + = 1.00 x 10-7 M

40 Density Gas low density of molecules Liquid medium density of molecules Solid high density of molicules

41 Density The mass of a substance of interest per unit of volume Symbol = ρ (lower case rho ) Unit kg/m 3 - official/si g/ml - common

42 Density Water The mass of a substance of interest per unit of volume 1 cubic meter (m 3 ) of water weighs 1000 Kg 1000 Kg = 1 metric tonne

43 Specific Gravity Density Specific Gravity The ratio of the density of a object in question to the density of water Water has a density of 1000 kg/m 3 Ethanol has a density of 789 kg/m 3 Specific Gravity (SG) Ethanol = 789/1000 = Gold has a density of g/cm 3 Water has a density of g/cm 3 Specific Gravity (SG) gold = 19.32/1.000 = 19.32

44 Cointreau (SG) Density The B52 Irish Cream 1.11 (SG) Kahlua 1.15 (SG)

45 Density What We Learned from The B52 Substances with lower specific gravity Float on top of things with higher specific gravity The Cointreau (SG = 1.04) floats on the Irish Cream (SG = 1.11)

46 Density Degrees Brix Density of sugar solutions measured in Degrees Brix Bx or B Mass Percentage Defined as grams Sucrose in 100 grams of solution Sucrose = Table Sugar = dimer of Glucose and Fructose A 24 B solution has the same density as 24 g of sucrose in 100 g of solution

47 Another Dead White Man Archimedes of Syracuse (c 287 c 212) Italy Greatest mathematician of antiquity Area of a circle, surface area & volume of a sphere Approximation of π Explained the principal of the lever Archimedes principal The upward buoyant force that is exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces

48 Will It Float? When an object is put in water, the water moves out of the way is displaced If an object floats, the weight of the water displaced is more than the weight of the object A more dense object (MORE MASS/less volume) will displace less water and sink A less dense object (less mass/more VOLUME) will displace more water and float

49 Will It Float? Late Show with David Letterman 12/17/2004

50 Measuring Density The Hydrometer Hydrometry flips the relationship now the density of the thing floating is fixed and the density of the fluid changes The hydrometer floats at a level where the weight of the fluid displaced equals the force holding up the hydrometer So less dense fluids (less mass/more VOLUME) would exert less force, so hydrometer sinks So more dense fluids (MORE MASS/less volume) would exert more force, so hydrometer rises

51 Measuring Density The Hydrometer Less dense fluids (less mass/more VOLUME) would exert less force, so the hydrometer sinks 1.0 B solution More dense fluids (MORE MASS/less volume) would exert more force, so the hydrometer rises 25.0 B solution

52 Measuring Density Lots of Units Same Concept Specific Gravity Ratio of the density of what is being measured to that of water ρ = g/cm 3 for water ρ = g/cm 3 for ethanol SG ethanol = 0.789/1.000 = 0.789» Note lack of units Brix Grams of Sucrose per 100 g of 20 C Balling Grams of Sucrose per 100 grams of water Baumé Grams of NaCl per 100 g of NaCl solution Oechsle Difference in weight of 1 L of solution vs. 1 L of water Plato Grams of Sucrose per 100 g of 17.5 C

53 Measuring Density Lots of Units Same Concept Specific Gravity Base Unit used universally Brix ( B) Used in USA and in Sugar/Candy/Carbonated Beverage Industry Balling Used in South Africa Baumé ( Be) Used in Australia and Europe Useful as it gives potential Alcohol (ml ethanol/100 ml wine) Oechsle ( Oe) Used in Germany, Switzerland and Luxembourg Plato Used in brewing Conversions 20.0 Brix = (SG) = 11.1 Baumé = 83 Oechsle = 19.7 Plato

54 Next Week Chemical Equilibrium ph TA