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Chapter 12: Solutions- General Comments

Chapter 12: Solutions- General Comments. 1. Solution: Solute Solvent Unsaturated NaCl (s)  Na + (aq) + Cl (aq) Saturated NaCl (s)  Na + (aq) + Cl (aq) 2. POINT OF SATURATION. Properties of Solutions: General Comments. 3. Solution formation:

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Chapter 12: Solutions- General Comments

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  1. Chapter 12: Solutions- General Comments • 1. Solution: • Solute • Solvent • Unsaturated • NaCl(s) Na+(aq) + Cl (aq) • Saturated • NaCl(s) Na+(aq) + Cl (aq) • 2. POINT OF SATURATION

  2. Properties of Solutions: General Comments • 3. Solution formation: • Intermolecular forces become rearranged. • NaCl(s) Na+(aq) + Cl (aq) • Intermolecular forces are attractive forces between molecules. • 4. Consider NaCl (solute) dissolving in water (solvent): • the water H-bonds have to be interrupted, • NaCl dissociates into Na+ and Cl-, • ion-dipole forces form: Na+…-OH2 and Cl- …+H2O.

  3. Consider NaCl (solute) dissolving in water (solvent): • the water H-bonds have to be interrupted, • NaCl dissociates into Na+ and Cl-, • ion-dipole forces form: Na+…-OH2 and Cl- …+H2O.

  4. Properties of Solutions: General Comments

  5. Generally: “like dissolves like” • Consider the addition of NaCl to water • The sodium and chloride ions are hydrated or surrounded by water molecules • The general term for surrounding a solute particle by solvent molecules is solvation

  6. TERMS USED IN DESCRIPTIONS OF SOLUTIONS • Solute: Solid, Liquid, or Gas • Solvent: Usually Liquid • Terms: Liquid Solute in Liquid Solvent • Miscible • Immiscible

  7. TERMS USED IN DESCRIPTIONS OF SOLUTION FORMATION • SOLVATION: The general term for surrounding a solute particle by solvent molecules is solvation • HYDRATED

  8. SOLUTION FORMATION • INTERMOLECULAR FORCES FOR SOLUTE, SOLVENT MUST BE BROKEN • INTRAMOLECULAR FORCES BETWEEN SOLUTE AND SOLVENT MUST FORM

  9. Solution Formation: Energy Considerations • There are three energy steps in forming a solution: • separation of solute molecules (H1): ENDOTHERMIC • separation of solvent molecules (H2): ENDOTHERMIC • formation of solute-solvent interactions (H3). Must be exothermic for solution to form

  10. ENTHALPY (H) • EXOTHERMIC - Hreaction • ENDOTHERMIC +Hreaction

  11. Solution Formation: Energy Considerations • 6. Enthalpy change in the solution process is Hsoln = H1 + H2 + H3. • Hsoln is Heat of Solution. can either be positive or negative depending on the intermolecular forces.

  12. Figure 12.2

  13. Factors Affecting Solubility: Effect of Temperature

  14. Figure 12.3

  15. Factors affecting Solubility: Temperature • Unsaturated • NaCl(s) Na+(aq) + Cl (aq) • Saturated NaCl(s) Na+(aq) + Cl (aq)

  16. Factors affecting Solubility: Temperature • If a “stress” is applied to an equilibrium by increasing the temperature, the equilibrium will shift in a way to minimize the stress • If heat is absorbed when solute dissolves, the solubility increases when the temperature is increases

  17. Pg 514

  18. Factors Affecting Solubility: Pressure • Henry’s Law • Sg = kPg

  19. Factors Affecting Solubility: Chemical Interactions • Enthalpy change in the solution process is Hsoln = H1 + H2 + H3. • Hsoln is Heat of Solution. can either be positive or negative depending on the intermolecular forces.

  20. Factors Affecting Solubility: Temperature

  21. Factors Affecting Solubility: Chemical Interactions • Hsoln = H1 + H2 + H3. • polar solvents dissolve polar solutes. • Non-polar solvents dissolve non-polar solutes.

  22. Factors Affecting Solubility: Chemical Interactions • H1: Energy Required Separate Solute Molecules/Ions • Ionic Solutes: Lattice Energy • Molecular Solutes: Types of Molecular Forces Determine Strength Bonds

  23. Factors Affecting Solubility: Chemical Interactions • H2: Energy Required to Separate Solvent Molecules • Water: Hydrogen Bonds • Non Polar Solutes • Induced Dipole • Dipoles

  24. Factors Affecting Solubility: Chemical Interactions • H3: Energy to Promote Solute Solvent Intereactions • Polar Solutes With Polar Solvents • Ionic Solutes • Molecules Containing Oxygen, Nitrogen, Phosphorus • CH3CH2-OH CH3CH2CHCO2H • NH2

  25. Factors Affecting Solubility: Chemical Interactions • Molecular, Polar, Solutes With Polar Solvents • Proportion of Polar Area to Nonpolar Area can Vary • CH3CH2-OH • CH3CH2CH2-OH • CH3CH2CH2CH2-OH • CH3CH2CH2CH2CH2CH2CH2-OH

  26. Problem 12.10: Tenth Edition • Explain why ethanol (C2H5OH) is not soluble in cyclohexane (C6H12)

  27. Collodial Dispersions • Dispersing Medium • Dispersed Phase

  28. Table 12.4

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