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Coulombs Law
- E = (constant) x q1q2/r
- q = charge of ions
- r = size of atom
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Molecule interactions in order of strength (strongest to weakest)
- ion-ion
- ion-dipole
- H-bonding
- dipole-dipole
- dispersion
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Surface tension of a liquid
- E required to increase surface tension by a unit
- increased temperature = decreased surface tension
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Capillary action
- Liquid will rise into a small tube / form meniscus
- cohesive forces: liquid attracts to itself
- adhesive forces: liquid adheres to non liquid
- mercury has very little adhesive force, resulting in a convex meniscus
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Vaporization Energy
- ΔHvap
- Amount of energy required to separate a molecule from the liquid (boil)
- ΔHvap increase = stronger intermolecular forces
- Larger surface area = faster rate of evaporation
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Vapor pressure
- Pressure in a closed container from molecules that have vaprorized from liquid within (they can't escape, so they create pressure)
- Higher vapor pressure = weaker intermolecular forces (more easily vaporized = more molecules in air = more vapor pressure)
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Viscosity
- Resistance of liquid to flow
- 1 poise = 1P = 1g/cm x seconds
- H2O is 1 cP at room temperature
- Larger viscosity = larger intermolecular forces
- more spherical molecular shape = decreased viscosity (less surface to surface contact)
- increased temperature = decreased viscosity (increase to average kinetic energy, easier to overcome flow)
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Phase diagrams
- Regions represent states, lines represent state changes
- Critical point: the furthest point on a vapor pressure curve
- Triple point: temperature/pressure where all 3 states exist simulatenously
- Normal BP, FP, etc = pressure @ 1 atm.
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Supercritical fluid
- Substances past the critical point on a phase diagram
- State that has some liquid properties and some gas properties
- Made from sealed liquid being heated, increased pressure, increased vapor density, decreased liquid density... essentially they all merge.
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Henry's Law
- Sgas=KHPgas
- S = solubility, KH = Henry's Law constant (different for each gas), P = pressure
- As pressure increases, gas solubility increases
- As pressure decreases, gas solubility decreases
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Temperature effects on liq/liq solubility and liq/gas solubility
- Two liquids: temp increase = solubility increase, temp decrease = solubility decrease
- Gas in liquid: temp increase = solubility decrease, temp decrease = solubility increase
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Vapor pressure (solvent in sol vs pure solvent)
- Vapor pressure of solvent in solution is LESS than vapor pressure of pure solvent
- solute replaces some particles @ surface, reduce amount vaporization, decrease amount of vapor
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Raoult's Law
- Psolvent in sol=Xsolvent x P0
- P = pressure, X = mole fraction, P0 = pressure of pure solvent
- Vapor pressure calculation
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Freezing Point Depression
- ΔTf = m x Kf x i
- m = molality, Kf = freezing point constant (
- °C/m), i = van't hoff factor
- F.p. sol lower than F.p. pure solvent
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Boiling point elevation
- ΔTf = m x Kb x i
- m = molality, Kb = boiling point constant (
- °C/m), i = van't hoff factor
- B.p. sol higher than B.p. pure solvent
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Osmotic pressure
- Π = MRTi
- M = molarity, R = .0821 atm L / mol K, T = temp in K, i = van't hoff factor
- amount of pressure needed to prevent osmotic flow
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van't hoff factor
- i
- amount of dissociation that occurs in solution
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