Thermo Lecture 7 Flashcards
What is a solution?
Solutions are made up of components that can vary in content independently of eachother. They can be solid, liquid or gas
What is Dalton’s Law?
What are the assumptions?
Pi = yi P
Partial pressure = mole fraction in gas mixture*pressure
Assumptions:
gas phase, no intermolecular forces
Define an ideal solution?
No interaction between the molecules of different components. ΔH mixing = 0 and ΔVmixing = 0.
They obey Raolts Law for all compositions
What is Raolt’s Law?
The partial pressure of a component = mole fraction of the component in the liquid (condensed) phase * vapour pressure of the component
Pi = xi*Pvi
When is Raolt’s Law valid?
When xi is close to 1 (solvent is nearly pure)
Valid for solvent when solution is dilute
What is Henry’s Law?
Partial Pressure = Henry’s constant mole fraction in solution
Pi = Hixi
When is Henry’s Law valid?
Low values of xi (Solvent is very dilute)
The solute in a dilute solution.
What is Activity, a?
ai = γixi Activity = activity coefficient *mole fraction
Give the formula for fugacity
limP->0 (fi/xiP) = 1
At equilibrium, what is the sum of the chemical potentials multiplied by the stoichiometric coefficients of all components in the system equal to?
zero
At equilibrium, what can be said about the relationship between the chemical potential of the same component that are in different phases to each other?
the chemical potentials are equal (otherwise would have mass transfer)
What is the formula for chemical potential of a component in a solution?
μ_i,P,T = μ_i,P,T (pure component) + RTln(P_i/P)
where P_i/P =x_i
*μ’s must be in same phase
What is the formula for chemical potential of a component in a non-ideal solution?
μ_i,P,T = μ_i,P,T (pure component) + RTln( γ_i*x_i)
where γ_i*x_i = a_i (activity)
*μ’s must be in same phase
