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1

Solution

Homogenous mixture of two or more substances

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Solvent

Major component in solution

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Solute

Minor component in solution

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Aqueous Solution

- Water is solvent

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Solubility

Amount of substance that will dissolve in given amount of solute

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Entropy

- Measure of energy randomization/dispersal in a system - Tendency is for energy to spread out/disperse whenever unrestrained

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Intermolecular Forces

- Dispersion: Weak - Dipole-Dipole: Separation of charges lead to electrostatic attraction - Hydrogen bond: Observe what H is bonded to; different in electronegativity - Ion dipole: Electrostatic force between ion and neutral molecule with dipole

8

Solution Interactions

- Solute-Solvent: Interactions between solvent particles and solute particles - Solvent-Solvent: Interactions between solvent particle and another solvent particle

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Interactions and Formation

- Solvent-Solute > Solvent Solvent and Solute-Solute Interactions = Solution Formation - Solvent-Solute = Solvent-Solvent and Solute-Solute = Solution formation - Solvent-Solute < Solvent-Solvent and Solute-Solute = may or may not form

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Polar Solvent Examples

- Water, acetone, methanol, ethanol

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Non polar solvent examples

- hexane, diethyl ether, toluene, carbon tetrachloride

12

Hess's Law

Overall enthalpy change upon solution formation is sum of enthalpy ∆Hsoln = ∆Hsolute + ∆Solvent + ∆Hmix (endothermic) - If ∆Hmix is more than the remaining, heat of solution is negative (exothermic)

13

Heat of Hydration

- Enthalpy change when 1 mol of gaseous solute ions are dissolve in H2O - Typically negative ∆Hsoln = ∆Hsolute + ∆Hydration - Take absolute value of ∆Hsoln and ∆Hhydration to compare; if solute is more, amount of E to separate solute into constituent ions is less than energy given off when an ion is hydrate (process is exothermic)

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Dynamic Equilibrium

- Rates of dissolution and recrystallization become equal

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Saturated solution

- Solution in which dissolved solute is in dynamic equilibrium with solid solute (undissolved)

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Unsaturated solution

Solution containing less than equilibrium amount of solute

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Supersaturated solution

One containing more than equilibrium amount of solute; often unstable and excess solute precipitates out

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Effect of temperature on solids in H2O?

- Solubility of most solids in water increases with increasing temperature

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Factors affecting solubility of gases in H2O?

- Temperature: Solubility of gases in liquids decrease with increasing temperature - Pressure: Higher the pressure of a gas above a liquid, the more soluble it becomes

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Henry's Law

Sgas = kHpgas

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Dilute solution

Contains small quantities of solute relative to amount of solvent

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Concentrated solution

Contains large quantities of solute relative to amount of solvent

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Molarity

(M) amount of solute (mol) / volume solution (L)

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Molality

(m) amount solute (mol) / mass solvent (kg) - Temperature independent

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Mole fraction (X)

amount solute (mol) / total amount solute + solvent (mol)

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Mole %

amount solute (mol) / total amount solute + solvent (mol) x 100%

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Parts by mass

mass solute / mass solution x multiplication factor

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Colligative properties

Properties that depend on number of particles dissolve in solution

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Vapor Pressure Lowering

VP of liquid = P of gas above the liquid when the two are in dynamic equilibrium

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Raoult's Law

Psolution = XsolventP˚solvent

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Two Component Solution

PA = XAA

PB = XbB

Total Pressure = Ptot = PA + PB

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Nonideal Solution

- Solute-solvent interactions are either stronger or weaker than solvent-solvent interactions

- If solute-solvent stronger: Solute tends to prevent solvent from vaporizing readily

- Solution is dilute: Effect = small

- Solution is not dilute = effect is significant 

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Freezing Point Depression

∆T= m x Kf

- Tf = change in temp in celsius

- m = molality

- Kf = freezing point depression

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Osmosis

- Flow of one solvent from solution of lower solute concentration to one of higher concentration

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Semipermeable Membrane

- Membrane that selectively allows some substances to pass through but not others

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Osmotic Pressure Equation

π = MRT

- M - molarity

- T - Temperature in Kelvin

- R - Ideal gas constant (0.08206...)

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van Hoff Factor

- (i) Ratio of moles of particles in solution to moles of formula units dissolved

i = moles of particles in soln. / moles formula units

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van Hoff Factor Equations

∆Tf = im x Kf

∆Tb = im x Kb

π = iMRT

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