CH353
- Physical Chemistry I Spring 2013, Unique 52575 Lecture Summary, 27 February 2013 |

Phase
diagrams: The slope of a phase
diagram is defined by the Clapeyron equation:d P/dT = deltaH(transition)/(T(transition)*deltaV(transition))This is a completely general equation for a transition between any two phases. If the transition involves the gas phase, we can estimate that V(g) >> V(other phase), and
so deltaV(transition) ~ V(g). This allows
us to plug the ideal gas law into the Clapeyron equation and
rearrange to find the Claussius-Clapeyron equation:d P/dT = PdeltaH(vap)/(nRT^2)While this equation is no longer exact, these simplifying assumptions have allowed us to formulate an equation that is very convenient to solve certain problems. This equation can be rearranged to the following: ln( P2/P1) = -(deltaH/R)*(1/T2
- 1/T1) |