vwt 272 class 7 - napa valley college 7.pdf · vwt 272 class 7 quiz 5 number of quizzes taken 26...

VWT 272 Class 7

Quiz 5

Number of quizzes taken 26

Min 12

Max 30

Mean 26.9

Median 28

Mode 30

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

(1824 – 1907)

Plan of Study

• The Mole

• Concentration

– Molarity

• Density

– °Brix

The Mole

The Mole The Chemists Dozen

• Counting Units

– A pair = 2 objects

– A dozen = 12 objects

– A gross = 144 objects

– A Ream = 500 objects

– A Mole = 6.0221408577 x 1023 objects


• Counting Units do not imply size

– A pair of stereo speakers is larger than a dozen eggs

>


• Counting units do not imply weight

– A gross of Finding Dory Caps weigh more than a ream paper


• A mole of something is 6.02 x 1023 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


• A mole of something is 6.02 x 1023 objects

Molecular Mass

• The Weight (in AMU) of a Molecule

– The sum of the weight of its component atoms

• AMU [u] = 1.660×10−27 kg

– Get Atomic Mass from the Periodic Table

Molecular Mass

• Example

– NaCl

• 22.990u + 35.453u = 58.443 u

• 58.443 u x 1.660×10−27 kg/u = 9.7×10−26 kg/molecule

• 0.00000000000000000000000097 kg/molecule

Molecular Mass

• Example

– Tartaric Acid (C4H606)

• (4 x 12.011u) + (6 x 1.008u) + (6 x 15.999u) = 150.086u

• 150.086u x 1.660×10−27 kg/u = 2.49×10−25 kg

• 0.000000000000000000000000249 kg/molecule

Molar Mass Gold

• The mass of one mole of each of the atoms in a compound

• Expressed in units of g/mol

– 6.0221 X 1023 atoms of gold (Au) weigh 196.97g

– Au has a Molar Mass of 196.97g/mol

Molar Mass Hydrogen Atom

• The mass of one mole of each of the atoms in a “compound”


– 6.022 X 1023 atoms of hydrogen (H) weigh 1.008g

– H has a Molar Mass of 1.008g/mol

Molar Mass Hydrogen Molecule

(H2)

• The mass of one mole of each of the atoms in a compound


– 6.022 X 1023 atoms of hydrogen (H) weigh 1.008g

– 2 atoms of H per molecule of H2 – H2 has a Molar Mass of 1.008g/mol + 1.008g/mol =

2.016 g/mol

Molar Mass • Examples

– Water (H2O)

• (1.008 x 2) + 16.00 = 18.02 g/mole

– Copper Sulfate (CuSO4)

• 63.54 + 32.06 + (4 x 16.00) = 159.6 g/mole

– Linalool (C10H18O)

• 154.3 g/mole

Molar Mass of LARGE molecules • Examples

– Tannic Acid (C76H52O46)

• 1701.19 g/mole

– Raspberry ellagitannin (C116H76O74)

• 2653.79 g/mole

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

Concentration Moose in Maine?


– Solute = Moose

– Solvent = the State of Maine (and 1 mile above it)

– 75,000 Moose in the State of Maine

• Maine (+ Atmosphere) = 35,385 mi3

• 75,000 moose/35,385 mi3 = 2.1 moose/mi3

• Unit Volume in this example = mi3

Concentration Bugs in Peanut Butter?


– 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

Concentration Oxygen in Air?


– Solute = Oxygen Gas (O2)

– Solvent = Air

– Dry air is 20.95% O2

– Unit Volume (implied) = 100 “units”

or

– 209.5 ml O2/L

– Unit Volume = 1 L

Concentration Dilute vs. Concentrated

• Generalized terms that refer to the amount of solute in a given amount of solvent

Concentration Concentrated vs. Saturated

• Saturated Solution – holds as much solute in solution as possible at a given

temperature

– g solute/100.0 ml H2O

Solute 0 °C 20 °C 40 °C 60 °C 80 °C

Sucrose C12H22O11 181.9 201.9 235.6 288.8 365.1

Sodium Cloride

NaCl 35.65 36.00 36.37 37.04 37.93

Concentration Concentrated vs. Saturated

• Saturated Solution

– holds as much solute in solution as possible at a given temperature

Concentration curve for solids into liquids

Concentration Supersaturated

• Supersaturated Solution

– holds more solute in solution than can be dissolved at a given temperature

Concentration Supersaturated


– 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

Concentration Supersaturated - Sodium Acetate


– holds more solute in solution than can be dissolved at a given temperature

– Sodium Acetate – C2H3NaO2 or CH3COONa

Concentration Supersaturated - Sodium Acetate

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

Concentration Supersaturated with Gas


– 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

Concentration Supersaturated with Gas

Concentration Gas Implications for Wine

• Cold Wine • Oxygen more likely to dissolve and stay in solution in cold wine

– Cold Stability

Concentration Gas Implications for Wine

• Sparkling Wine • Disgorge at a lower temperature = less loss of CO2 bubbles

• Difficulty in measuring bubble rate – No “standard glass”

– Cellulose fibers from towel

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)

Molarity

• Examples

– 0.80 moles of Acetic Acid (C2H4O2) in 1.000 L of water

• 0.80 M – commercial vinegar

– Sea Water contains about 28.0 g of NaCl per L

• Molar Mass of NaCl is 58.44 g/mole – 28.0 g x 1 mole/58.44 g = 0.479 mole = 0.479M

Molarity

• More Examples

– Sea Water contains from 0 to 20 mg/L oxygen (O2)

• Molecular mass of O2 is 32.0 g – 6.2x10-4 M

– 2 cubes of sucrose (C12H22O11) in a mug of tea

• 1 cube = 4 g 1 mug = 350 ml – 0.067 M

Molarity

• Yet more Examples

– 159.9 g CuSO4 dissolved in 1.000 L water




Molarity

• Water can be BOTH a Bronsted-Lowry Acid or a Bronsted-Lowry Base at the same time

– Concentration of H3O+ = 1.00 x 10-7 M

Density

• Gas – low density of molecules

• Liquid – medium density of molecules

• Solid – high density of molicules

Density

• The mass of a substance of interest per unit of volume

• Symbol = ρ (lower case “rho”)

• Unit – kg/m3 - official/SI

– g/ml - common

Density Water

• The mass of a substance of interest per unit of volume

• 1 cubic meter (m3) of water weighs 1000 Kg

• 1000 Kg = 1 metric tonne

Density Specific Gravity

• Specific Gravity

– The ratio of the density of a object in question to the density of water

– Water has a density of 1000 kg/m3

– Ethanol has a density of 789 kg/m3

• Specific Gravity (SG) Ethanol = 789/1000 = 0.789

– Gold has a density of 19.32 g/cm3

– Water has a density of 1.000 g/cm3

• Specific Gravity (SG) gold = 19.32/1.000 = 19.32

Density The B52

• Cointreau - 1.04 (SG)

• Irish Cream – 1.11 (SG)

• Kahlua – 1.15 (SG)

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)

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

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

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

Will It Float?

Late Show with David Letterman 12/17/2004

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

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

Measuring Density Lots of Units – Same Concept

– Specific Gravity • Ratio of the density of what is being measured to that of water

– ρ = 1.000 g/cm3 for water – ρ = 0.789 g/cm3 for ethanol – SG ethanol = 0.789/1.000 = 0.789

» Note lack of units

– °Brix • Grams of Sucrose per 100 g of solution @ 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 solution @ 17.5° C

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 = 1.083 (SG) = 11.1 °Baumé = 83 °Oechsle = 19.7 Plato

Next Week

• Chemical Equilibrium

• pH

• TA

vwt 272 class 7 - napa valley college 7.pdf · vwt 272 class 7 quiz 5 number of quizzes taken 26...

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