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Solutions

Solutions. SOLUTE + SOLVENT SOLUTION. State of Matter. Gas:. homogenous mixture of gases (Air…). Liquid:. solvent: liquid solute: gas solid. (soda water: CO 2 /H 2 O; brine: NaCl/H 2 O). solvent: liquid solute: liquid (ethanol in water). Solid:.

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Solutions

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  1. Solutions

  2. SOLUTE + SOLVENT SOLUTION State of Matter Gas: homogenous mixture of gases (Air…)

  3. Liquid: • solvent: liquid solute: gas • solid (soda water: CO2/H2O; brine: NaCl/H2O) • solvent: liquid solute: liquid • (ethanol in water)

  4. Solid: • solvent: solid solute: solid (gold-silver alloy) • solvent: solid solute: liquid (Dental-filling alloy)

  5. Terms to Know… Dissolve: solute + solvent  solution. Crystallization: solution  solute + solvent. Saturation: crystallization and dissolution are in equilibrium. Solubility: amount of solute required to form a saturated solution. Supersaturated: 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.

  6. + – + – NaCl – + – + + – + – octane water Like Dissolves Like “Rule”: polar solvents dissolve polar solutes. Non-polar solvents dissolve non-polar solutes. Why? If ΔHsoln 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.

  7. 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

  8. Supersaturated solutions:

  9. 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).

  10. Properties of Water • Most abundant liquid • Vital to life • Universal solvent 1. High melting and boiling points M.p.: 0.0°C B.p.: 100.0°C (0.1 MPa)

  11. H2O H2Te H2Se H2S SnH4 GaH4 SiH4 CH4 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.

  12. Water Molecule

  13. Solutions

  14. The melting point curve slopes to the left because ice is less dense than water. • Triple point occurs at 0.0098°C and 4.58 mmHg. • Normal melting (freezing) point is 0°C. • Normal boiling point is 100°C. • Critical point is 374°C and 218 atm. Phase Diagram of H2O

  15. 2. Density 0.0°C (ice) 0.91680 g/cm3 0.0°C (liquid) 0.99984 g/cm3 3.98°C 0.99997 g/cm3 25.0°C 0.99704 g/cm3 3. Surface tension: high Bottom of meniscus

  16. 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

  17. 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

  18. 3. Groundwater

  19. 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

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