announcements to join clicker to class today: – turn on the clicker (the red led comes on). –...
TRANSCRIPT
AnnouncementsTo join clicker to class today:
– Turn on the Clicker (the red LED comes on).
– Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful).
● Starting Chapter 10 next.
● Suggested reading and problems e-mailed to you and on class web site.
● Last exam (chp 9 & 10) one week from Friday.● Review material is posted.● Wear appropriate clothes to Lab!
Review• H-bonding
– Generally weaker than ion-ion interactions– Stronger than other intermolecular interactions.– Only seen for hydrogens bonded to N, O or F.– Bond to lone pair on another molecule (usually on N,
O or F).– Explain very high boiling points for H
2O, NH
3 and HF
• Solubility– “like dissolves like” (polar in polar, nonpolar in
nonpolar)– Only soluble if dissolved particles lower energy than
undissolved solid.
Raoult’s Law of Vapor Pressure• Raoult’s Law: Pvap = XsolventP˚solvent
– Pvap = vapor pressure of solvent above the solution
– Xsolvent = mole fraction of solvent particles in the solution
• note ntot
= nsolv
+ insolute
(may include + & - ions)
• Xsolvent=nsolv
/(nsolv
+ insolute
)
– P˚solvent = vapor pressure of pure solvent at the temperature of interest.
• Implication: increasing non-volatile solute concentration lowers the vapor pressure of the solvent.
Blocking of evaporation by solute
Fig 9.10
CO2 H
2O
Fig. 9.13Fig. 9.12
Water on a hydrophobic (nonpolar) surface
Picture courtesy of: The University of British Columbia Structured Surface Physics Laboratory
Surface Tension and Meniscus
Fig 9.15Fig 9.16