Solutions SOLUTE SOLVENT SOLUTION State of Matter Gas

Solutions

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

Liquid: qsolvent: liquid solute: gas solid (soda water: CO 2/H 2 O; brine: Na. Cl/H 2 O) qsolvent: liquid solute: liquid (ethanol in water)

Solid: qsolvent: solid (gold-silver alloy) solute: solid qsolvent: solid (Dental-filling alloy) solute: liquid

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.

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. Na. Cl in octane (C 8 H 18): the ion. London forces are weak because octane is non-polar. Therefore, the ion-London forces do not compensate for the separation of ions. Na. Cl dissolves nicely in water. + – – + + – Na. Cl octane water

Terminology: Solubility: is the maximum amount of the solute that will dissolve in a definite amount of solvent (at a given t°) g/100 m. L Concentration: ratio of the solute and the solvent Dilute solutions Concentrated solutions Saturated solutions: solutepure solute dissolved

Supersaturated solutions: g/100 m. L KNO 3 Pb. Cl 2 Na. Cl Solubility curves t°

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. Ce 2(SO 4)3).

Properties of Water q Most abundant liquid q Vital to life q Universal solvent 1. High melting and boiling points M. p. : 0. 0°C B. p. : 100. 0°C (0. 1 MPa)

Hydrogen Bonding q. Special case of dipole-dipole forces. q. By experiments: boiling points of compounds with H-F, H-O, and H-N bonds are abnormally high. q. Intermolecular forces are abnormally strong. H 2 O H 2 Te H 2 S H 2 Se Si. H 4 CH 4 Sn. H 4 Ga. H 4

Water Molecule

Solutions

Phase Diagram of H 2 O q. The melting point curve slopes to the left because ice is less dense than water. q. Triple point occurs at 0. 0098°C and 4. 58 mm. Hg. q. Normal melting (freezing) point is 0°C. q. Normal boiling point is 100°C. q. Critical point is 374°C and 218 atm.

2. Density 0. 0°C (ice) 0. 0°C (liquid) 3. 98°C 25. 0°C 3. Surface tension: 0. 91680 g/cm 3 0. 99984 g/cm 3 0. 99997 g/cm 3 0. 99704 g/cm 3 high Bottom of meniscus

4. High heat of vaporization 40. 70 k. J/mol 5. High heat of fusion 6. 02 k. J/mol 6. High specific heat 75. 20 k. J/mol

1. Chemically pure water 2. Water of crystallization or hydration Cu. SO 4 5 H 2 O(s) D Cu. SO 4(s) + 5 H 2 O(g) (Ca. SO 4)2 H 2 O (plaster of paris) Ca. SO 4 2 H 2 O (gypsum) Na 2 CO 3 10 H 2 O

3. Groundwater Cations Anions Ca 2+ HCO 3 -, CO 32 - Na+ OH- Mg 2+ SO 42 - K+ Cl- Fe 2+, Fe 3+ NO 3 - NH 4+ F-, PO 43 -

Hard water q q Soft water Temporary hard water HCO 3 - (bicarbonate) Permanent hard water Water Softening q q Boiling Softening agents q q Distillation Ion-exchange Mineral water Thermal water precipitation complex formation