chemistry 102(01) spring 2012

15-1CHEM 102, Spring 2012 LA TECH

CTH 328 9:30-10:45 am

Instructor: Dr. Upali Siriwardane

e-mail: [email protected]

Office: CTH 311 Phone 257-4941

Office Hours: M,W 8:00-9:00 & 11:00-12:00 am;

Tu,Th,F 8:00 - 10:00 am..

Exams: 9:30-10:45 am, CTH 328.

March 26 , 2012 (Test 1): Chapter 13

April 18 , 2012 (Test 2): Chapter 14 &15

May 14 , 2012 (Test 3): Chapter 16 &18

Optional Comprehensive Final Exam: May 17, 2012 :

Chapters 13, 14, 15, 16, 17, and 18

Chemistry 102(01) Spring 2012


Chapter 15. The Chemistry of Solutes and Solutions 15.1 Solubility and Intermolecular Forces 15.2 Enthalpy, Entropy, and Dissolving Solids 15.3 Solubility and Equilibrium 15.4 Temperature and Solubility 15.5 Pressure and Dissolving Gases in Liquids:

Henry's Law15.6 Solution Concentration: Keeping Track of Units15.7 Vapor Pressures, Boiling Points, and Freezing Points

of Solutions15.8 Osmotic Pressure of Solutions15.9 Colloids 15.10 Surfactants15.11 Water: Natural, Clean, and Otherwise


Solution TerminologySoluteone or more substance(s) dispersed in the solution

Solventmajority substance in a solutionThe solubility of a solid in a solvent is typically given in

g/100 ml.

Types of solutionsMixture of GasesLiquid solutions (L+S,L+L,L+G)Solid solutions (S+S, alloys)Aerosols (L+G)Foam (S+G)


Miscible vs. Immiscible


“Likes Dissolve Likes”Materials with similar polarity are soluble in

each other. Dissimilar ones are not.Polar substances with similar forces are likely

to be soluble in each otherNon-polar solutes dissolve in non-polar

solventsstronger solute-solvent attractions favor

solubility, stronger solute-solute or solvent-solvent attractions reduce solubility


Solubility of Ionic Compounds and Temperature


Solution Terminology

Miscible - liquids that dissolve in each otherImmiscible - liquids that do not dissolve in each

other due to differences types of interactionsSaturated solutionA solution that contains as much it can hold Unsaturated solutionA solution that contains less than maximum

amountSupersaturated solution A solution that contains more than maximum

amount


Types of Solutions (Diluted, Saturated, and Supersaturated)


Supersaturated Solution


Solute - Solvent Interactions


The Solution Making Exopthermic Process


The Solution Making Endothermic Process


Thermodynamic Factors Affecting Solubility

1. Energy: Enthalpy (DH) Lower energy – DH

2. Order: Entropy (DS) Disorder + DS

Exothermic –DH favors solubility: product favored

Mixing (+DS disorder favors solubility: product favored

Gibbs Free Energy: (Chapter 18)

DGsoln = DHsoln -TDSsoln,


Types of Solute - Solvent Interactions

All interactions are electrostatic force

~ Coulombic: proprotional to charge and séparation)

1. London Dispersion Forces: (O2 dissolved in Liq. N2)

2. Ion-Ion Interaction: (Ionic liquids in batteries)

3. Ion-Dipole Interaction (hydrated ions Na+

(aq))

4. Dipole-Dipole Interaction (CCl4 in benzene (C6H6)

5. Hydrogen Bonding. (water and éthanol)


1) What are the main factors affecting a solubility of a solute in a solvent?


The Solution Making Exopthermic Process


The Solution Making Endothermic Process


2) Arrange the following inter-particles forces in liquids and solids in the order of increasing strength:

• ion-ion, • ion-dipole, • hydrogen bond, • dipole-dipole and • London dispersion


3) Identify the most important type of inter-particle force for each of the following compounds:

a) NaCl(s) or NaCl(l) b) N2(l) or N2(s) c) N2(g) d) Na(s) and Na(l)

e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)


4) Which of the above inter-particle force could be named as intermolecular force?

a) NaCl(s) or NaCl(l) b) N2(l) or N2(s) c) N2(g) d) Na(s) and Na(l)

e) H2O(l) or H2O(s) f) CH3CH2OH(l) or CH3CH2OH(s)


Acetic acid

HC2H3O2

CH3COOH

Hexanol

C6H13OHHexane

C6H14

Propanoic acid

C2H5COOH

“Like Dissolves Like”

Identify Hydrogen Bonding, Polar and Non-polar groups in Covalent Molecules


5) What types of inter-particle forces solute-solute:DH1, solvent-solvent: DH2, solvent-solute:DH3) are involved when a) CH3CH2OH(l): dissolved in water,H2O:DH1 = ; DH2 = ; DH3= For covalent compounds: DHsoln= DH1+ DH2+ DH3


Water Dissolving An Ionic Solute


Solution Process of Ionic Compounds


Hydration of a Sodium Ion


Heats of Solution


4) b) Na2SO4(s) dissolved in water:DH1 = ; DH2 = ; DH3 = Ion-ion inter-particle forces in solids are called

Lattice Energy. ( this is related to DH1)Ion-water inter-particle forces are called Hydration

Energy (this is related to DH2 and DH3) For ionic compounds; DHsoln = DHlattice + DHhyd

Qualitatively speaking which of the above a) or b) would have a more exothermic DHsoln?


4) What factors make it more exothermic? a) CH3CH2OH in H2O DH1 = ; DH2 = ; DH3=

b) Na2SO4(s) dissolved in water: (DH1 = DHsoln)+ (Hhyd= DH2+ DH3)


5) Assign the entropy (most +, medium + or least +) for i) S1 –solute: ii) S2-solvent:iii) S3, solution (solvent-solute):

For the following: (Indicate which one is highest, intermediate and lowest order) For

a) CH3CH2OH(l): dissolved in water: S1 = ; S2 = ;S3= Na2SO4(s) dissolved in water: S1 = ; S2 = ;S3 =


5) Qualitatively speaking which of the above a) or b) would have a more positive DSsoln?

a) CH3CH2OH(l): dissolved in water: S1 = ; S2 = ;S3= b) For Na2SO4(s) dissolved in water: S1 = ; S2 = ;S3 =


6) Calculate the DHsoln for dissolving CaCl2(s) in water given the Lattice-Energy CaCl2(s) = +2258 kJ/mole), and Hydration energy for CaCl2 = - 2205 kJ/mole (DHsoln = DHlattice + DHhyd =?)


7) DHsoln value thermodynamically product favored?


8) For dissolving CaCl2(s) in water, which of the following entropy represent the highest order? Explain.a) S for CaCl2(s): +104.6 J/mole

b) S for H2O(l): +69.91 J/mole

c) S for solution CaCl2(aq): +815 J/mole


9) Calculate the DSsoln for dissolving CaCl2(s) in water given the entropies of Lattice- CaCl2(s) (S1= +104.6 J/mole), H2O(l)(S2 = +69.91 J/mole); CaCl2(aq)(S3 = +815 J/mole).

DSsoln= Sfinal-Sinitial =S3 - ( S1+ S2)?


10) Calculate the DSsoln for dissolving CaCl2(s) in water given the entropies of Lattice- CaCl2(s) (S1= +104.6 J/mole), H2O(l)(S2 = +69.91 J/mole); CaCl2(aq)(S3 = +815 J/mole).

DSsoln= Sfinal-Sinitial =S3 - ( S1+ S2)?


11) DSsoln value thermodynamically product favored?


12) Based on DGsoln, determine if CaCl2 is soluble at 25C, given,

DGsoln = DHsoln -TDSsoln, and DHsoln and DSsoln calculated above.


13) Why sand is insoluble in both polar and nonpolar solvents?


14) How does temperature and pressure affect the solubility of following?

a) NH4NO3(solid) in water with +(positive) DHsoln:

b) CO2 gas in water:


Solubility of Oxygen in Water


Henry’s Law


Henry’s LawSolubility of Gases in SolventsSg = kHPg

where Sg solubilitykH Henry’s Law constantPg partial pressure of gas

Increasing the pressure of a gas above a liquid increases its solubility


15) Deep sea divers may experience a condition called the "bends" if they do not readjust slowly to the lower pressure at the surface. Using the diagram on pressure dependence solubility of gases on water explain this phenomenon.

chemistry 102(01) spring 2012

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