Solutions

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Solutions
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SOLUTE SOLVENT SOLUTION
State of Matter
Gas
homogenous mixture of gases (Air)
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Liquid

• solvent liquid solute gas
• solid

(soda water CO2/H2O brine NaCl/H2O)

• solvent liquid solute liquid
• (ethanol in water)

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Solid

• solvent solid solute solid
• (gold-silver alloy)

• solvent solid solute liquid
• (Dental-filling alloy)

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Terms to Know
Dissolve solute solvent ? solution. Crystalliza
tion solution ? solute solvent. Saturation
crystallization and dissolution are in
equilibrium. Solubility amount of solute
required to form a saturated solution. Supersatura
ted a solution formed when more solute is
dissolved than in a saturated solution. Miscible
two liquids that mix. Immiscible two liquids
that do not mix.
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Like Dissolves Like
Rule polar solvents dissolve polar solutes.
Non-polar solvents dissolve non-polar solutes.
Why? If ?Hsoln is too endothermic a solution will
not form. NaCl in octane (C8H18) the ion-London
forces are weak because octane is non-polar.
Therefore, the ion-London forces do not
compensate for the separation of ions. NaCl
dissolves nicely in water.
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Terminology
Solubility is the maximum amount of the
solute that will dissolve in a
definite amount of solvent (at a given t)
g/100 mL
Concentration ratio of the solute and the
solvent
Dilute solutions Concentrated solutions Saturated
solutions
solutepure solute dissolved
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Supersaturated solutions
g/100 mL KNO3 PbCl2

NaCl

Solubility curves t
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Temperature Effects Solids

• Experience tells us that sugar dissolves better
  in warm water than cold.
• As temperature increases, solubility of solids
  generally increases.
• Sometimes, solubility decreases as temperature
  increases (e.g. Ce2(SO4)3).

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Properties of Water

• Most abundant liquid
• Vital to life
• Universal solvent

1. High melting and boiling points M.p.
0.0C B.p. 100.0C (0.1 MPa)
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Hydrogen Bonding

• Special case of dipole-dipole forces.
• By experiments boiling points of compounds with
  H-F, H-O, and H-N bonds are abnormally high.
• Intermolecular forces are abnormally strong.

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Water Molecule
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Solutions
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Phase Diagram of H2O
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2. Density 0.0C (ice) 0.91680
g/cm3 0.0C (liquid) 0.99984 g/cm3 3.98C 0.9
9997 g/cm3 25.0C 0.99704 g/cm3
3. Surface tension high
Bottom of meniscus
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4. High heat of vaporization 40.70 kJ/mol
5. High heat of fusion 6.02 kJ/mol
6. High specific heat 75.20 kJ/mol
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1. Chemically pure water
2. Water of crystallization or
hydration CuSO4 5H2O(s) CuSO4(s)
5H2O(g) (CaSO4)2 H2O (plaster of
paris) CaSO4 2H2O (gypsum) Na2CO3 10H2O
D
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3. Groundwater
Cations Anions
Ca2 HCO3-, CO32-
Na OH-
Mg2 SO42-
K Cl-
Fe2, Fe3 NO3-
NH4 F-, PO43-
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Hard water Soft water

• Temporary hard water
• HCO3- (bicarbonate)
• Permanent hard water

Water Softening

• Boiling
• Softening agents precipitation
• complex formation
• Distillation
• Ion-exchange
• Mineral water
• Thermal water