Lecture 16 Flashcards
Tm= (Stands for)
Melting point
Tb= (stands for)
Boiling point
In order from weakest to strongest, attraction forces
Gas<Liquid<Solid (weakest<moderate<strongest)
Phase changes- Melting
Include endo vs exo and delta H, and units of measure
Solid->Liquid (Endothermic), deltaH>0, Tm and -kJ/mol
Phase changes-Condensation
Include endo vs. exo and delta H, and units of measure
Gas -> Liquid (exothermic), DeltaH<0
Phase Changes-Sublimation
Include exo vs endo, deltaH, and units of measure
Solid-> Gas, (Endo OR exo -depends on the composition), Troom=22-25C/298.15K
Phase changes-Evaporation
Include Exo vs Endo, delta H and volatile vs nonvolatile liquids
Liquid-> Gas (endothermic usually), delta H>0
Volatile = liquids evaporate quickly
non volatile = do not evaporate quickly
Phase changes -Freezing
Include endo vs exo, delta H, and units of measure
Liquid-> Solid (Exothermic), deltaH<0, Tf (comp) ex: Tf(H20)=0C/273.26K
Phase changes-Boiling
Include endo vs exo, delta H, and units of measure
Liquid-> Gas (endothermic), deltaH>0, Tb (H20 =100C/373.15K
Surface tension definition
Liquids tend to minimize their surface *Resists penetration
*Stronger attraction =larger surface tension
Surface tension equation
Surface Tension = Force (N) x Surface Area (m^2)
Viscosity definition and qualities
Resistance of a liquids flow like oils.
Less round molecules shape =larger viscosity and also depends on number of carbons and Prescence of double bonds
Vapor Pressure definition
The partial pressure exerted by the vapor
Boiling point depends on
atmospheric pressure
Vaporization units
Pvap deltaHvap=kJ/Mol and requires 40.7 kJ of heat to vaporize one mole of water @100C
deltaH condensation =-deltaH vaporization
Hess’s Law
Enthalpy of a chemical process is independent of the path taken from the initial to the final state (i.e. enthalpy is a state function)
Or, DeltaH depends on HF (H formation) of reactants and products and doesn’t depend on the HF of the intermediate steps.
Hess’s Law equation
DeltaH (RXN)=Sigma/kappa??HF (products)-Sigma/kappaHF(reactants)
Enthalpy definition
Amount of heat (KJ/Mol, J/mol)
Exothermic definition and unit
Heat released. DeltaH-RXN<0. Product is less than original reaction because heat is released.
P-R= T-#
Endothermic reaction definition
Heat/energy absorbed. DeltaH-RXN >0. Product=More bc energy absorbed. P-R=T+#
pound sign meaning in enthalpy equation
Activated complex
Hf Simple units/equation
0kJ/Mol
Example: DeltaH RXN=2HF (CO) - [2 HF (C) +1 HF (O)= 2 x (-150.00)- [2.0 + 1.0] = -300.0 kJ/Mol (exothermic since - number)
Stoichiometry of DeltaH RXN
G x Moles/Molarmass x kJ/Mol bc deltaH is measured in kJ/Mol