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: –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 + …  -OH 2 and Cl - …  +H 2 O.

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 + …  -OH 2 and Cl - …  +H 2 O.

Properties of Solutions: General Comments

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

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

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

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

Solution Formation: Energy Considerations There are three energy steps in forming a solution: –separation of solute molecules (  H 1 ): ENDOTHERMIC –separation of solvent molecules (  H 2 ): ENDOTHERMIC –formation of solute-solvent interactions (  H 3 ). Must be exothermic for solution to form

ENTHALPY (H) EXOTHERMIC -  H reaction ENDOTHERMIC +  H reaction

Solution Formation: Energy Considerations 6. Enthalpy change in the solution process is  H soln =  H 1 +  H 2 +  H 3.  H soln is Heat of Solution. can either be positive or negative depending on the intermolecular forces.

Figure 12.2

Factors Affecting Solubility: Effect of Temperature

Figure 12.3

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

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

Pg 514

Factors Affecting Solubility: Pressure Henry’s Law S g = kP g

Factors Affecting Solubility: Chemical Interactions Enthalpy change in the solution process is  H soln =  H 1 +  H 2 +  H 3.  H soln is Heat of Solution. can either be positive or negative depending on the intermolecular forces.

Factors Affecting Solubility: Temperature

Factors Affecting Solubility: Chemical Interactions  H soln =  H 1 +  H 2 +  H 3. polar solvents dissolve polar solutes. Non-polar solvents dissolve non-polar solutes.

Factors Affecting Solubility: Chemical Interactions  H 1 : Energy Required Separate Solute Molecules/Ions –Ionic Solutes: Lattice Energy –Molecular Solutes: Types of Molecular Forces Determine Strength Bonds

Factors Affecting Solubility: Chemical Interactions  H 2 : Energy Required to Separate Solvent Molecules –Water: Hydrogen Bonds –Non Polar Solutes Induced Dipole Dipoles

Factors Affecting Solubility: Chemical Interactions  H 3 : Energy to Promote Solute Solvent Intereactions –Polar Solutes With Polar Solvents Ionic Solutes Molecules Containing Oxygen, Nitrogen, Phosphorus CH 3 CH 2 -OH CH 3 CH 2 CHCO 2 H NH 2

Factors Affecting Solubility: Chemical Interactions Molecular, Polar, Solutes With Polar Solvents Proportion of Polar Area to Nonpolar Area can Vary –CH 3 CH 2 -OH –CH 3 CH 2 CH 2 -OH –CH 3 CH 2 CH 2 CH 2 -OH –CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 -OH

Problem 12.10: Tenth Edition Explain why ethanol (C 2 H 5 OH) is not soluble in cyclohexane (C 6 H 12 )

Collodial Dispersions Dispersing Medium Dispersed Phase

Table 12.4