Chem 162-2011 Lecture 3 2PLAN FOR TODAY: DO LECTURE 2 LECTURE 3 PHYSICAL PROPERTIES OF SOLUTIONS •Solutions of electrolytes •Colloids CHEMICAL KINETICS •Chemical Kinetics – A Preview •The meaning of reaction rate •Measuring reaction rates
Chem 162-2011 Lecture 3 4FORMULASgsolute+ gsolvent= gsolutionmLsolute+ mLsolvent≠mLsolutionMass percent = grams of solute/100 g solution Mole percent = moles of solute/100 moles solution Molarity = moles of solute/L of solution ET: Molarity is temperature dependent, but molality is not. Difficult but important interconversion Molality = moles of solute/kilogram of solvent PPM = grams of solute/1,000,000 grams solution Volume percent = volume of solute/100 mL of solution Proof = 2 x Vol. %; e.g., 2 x 40 mL/100 mL solution = 80 proof Mole fraction: XA= nA/(nA+ nB) XA+ XB= 1 Particle fraction: PXA= inA/(inA+ inB) PXA+PXB= 1 Raoult’s law: Don’t use: Psoln= XsolventPosolventUse: Psoln= PXsolventPosolventFor two volatile components: Psoln= PXsolventAPosolventA + PXsolventBPosolventBPXsolvent= insolvent/(insolvent+ insolute) PXA+ PXB= 1 van’t Hoff factor, “i”; i = moles of particles in solution/moles of solute dissolved Boiling-point elevation: ΔT = Tf- Ti= KbimsoluteFreezing-point depression: ΔT = Tf- Ti= -Kfimsolute Osmotic pressure: πV = inRT* * Begin problem with this formula, not the equivalent π= iMsoluteRT ΔHsoln= ΔHsolute-solutebondbreaking+ ΔHsolvent-solventbondbreaking+ ΔHsolute-solventbondformingHenry’s Law: SA=kPA; MA= Solubility of dissolved gas in solution “S” may be any unit of concentration (depending on the units of “k”), e.g., X, M, %. ET note: Not everything goes through moles, e.g., volume to grams, grams to volume, atoms to molecules, molecules to atoms.