1. 11.3 Factors Affecting Solubility
Ch. 11 Solutions
11.3 Factors Affecting Solubility

2. Structure hydrophobic: water- fearing hydrophilic: water-loving
nonpolar
insoluble
hydrophilic: water-loving
polar
soluble

3. Pressure increases solubility of gases Henry’s Law: P=kC
C is concentration and P is partial pressure of gaseous solute
relationship between gas pressure and concentration of dissolved gas
amount of gas dissolved is directly proportional to P of gas above solution
obeyed best by dilute solutions of gases that don’t dissociate or react with solvent

4. Pressure

5. Example
A soft drink bottled at 25°C contains CO2 at pressure of 5.0 atm over liquid. Assume that PCO2 in atmosphere is 4.0 x 10-4 atm. Find the equilibrium concentration in soda before and after opening. k=32 L*atm/mol at 25°C

6. Example
before opening:
after opening:

7. Temperature dissolving a solid occurs faster at higher T
but the amount able to be dissolved does not change

8. Temperature
solubility of gas in water increases with lower T

9. 11.4 Vapor Pressures of Solutions
Ch. 11 Solutions
11.4 Vapor Pressures of Solutions

10. Vapor pressure-

11. Vapor Pressures of Solutions
nonvolatile solutes lower the vapor pressure of a solvent
the dissolved solute particles decrease the # of solvent molecules near the surface
so less solvent
molecules have
a chance to
escape into
gaseous phase

12. Raoult’s Law Psoln is the observed vapor pressure
Psolvent is the vapor
pressure of pure
solvent
linear graph
Psoln for y
solvent for x
Psolvent is m

13. Example
Find the vapor pressure at 25°C for solution of g of sucrose in mL of water. The density of water at 25°C is g/mL and the partial pressure of water vapor at 25°C is torr.

14. Example

15. Ideal Solution a liquid-liquid solution that obeys Raoult’s law
nearly ideal occurs when solute and solvent are very similar

16. Volatile Solutions when both components are volatile where
PA and PB are partial pressures
PA° and PB° are vapor pressure of pure A and B

17. Deviation from Raoult’s Law
negative deviation
ex. acetone and water
when solvent has special attraction to solute
observed vapor pressure will be lower than predicted

18. Deviation from Raoult’s Law
positive deviation
ex. ethanol and hexane
when solvent has especially weak interactions with solute
observed vapor pressure will be higher than predicted