announcements to join clicker to class today: – turn on the clicker (the red led comes on). –...

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