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					                                                       Maleckar
                                                       Chem 970
                                                     Spring 2012

Partial Notes
Chapter 12: Solutions

A solution is…..



Does it have to be a solid dissolved in a liquid?


All solutions have a solute and a solvent.

Solute:


Solvent:



      solution of gases


      gas dissolved in liquid
      many substances diss in water


      salt (solid) dissolved in water


      Gold-silver solution of two solids (Au & Ag)
Solvation

-

-


NaCl(s)  Na+(aq) + Cl-(aq)
Na+(aq) + Cl-(aq)  NaCl(s)

NaCl(s)        Na+(aq) + Cl-(aq)



Thermodynamics of Solvation

Step I. Solute molecules must separate.




Step II. Solvent molecules must separate to open spaces for the solute.




Step III. Formation of Solute-Solvent Particles
Solvation is a Balancing Act….




What about Hsolution?

   - It can be negative or positive…….
   - The sign of Hsoln doesn’t solely determine if something dissolves or not

      Ex: Hsoln is negative in heat packs
          Hsoln is positive in cold packs




Q: Why don’t oil and water mix?




How do soaps work?
Q: At what point does a solute stop dissolving in the solvent?
A:


Some thresholds:


NaCl:                   HCl:

sucrose:                H2SO4:



Intermolecular Forces and Solubility

                                          Solubility in 100g Water at 20°C

Methanol           CH3OH

Ethanol            CH3CH2OH

Propanol           CH3CH2CH2OH

Butanol            CH3(CH2)3OH

Pentanol           CH3(CH2)4OH

Hexanol            CH3(CH2)5OH

Heptanol           CH3(CH2)6OH

Octanol            CH3(CH2)7OH

Decanol            CH3(CH2)9OH
Sickle-cell anemia

What happens?
Temp, Pressure, and Solubility




Solubility of Gases
Henry’s Law

At a given temperature, the amount of gas dissolved in a solvent is directly
proportional to the pressure of the gas above the substance.

        Sg = kPg

Sg = solubility of the gas in the solution phase (M)
k = Henry’s Law constant
Pg = partial pressure of the gas over the solution


How many grams of carbon dioxide gas are dissolved in a 1 L bottle of
carbonated water if the manufacturer uses a pressure of 2.4 atm in the
bottling process at 25 °C? Given: KH of CO2 in water = 29.76 atm/(mol/L) at
25 °C.

				
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