State the equation for Δ_mix G (for an ideal solution)
Δ_mix G = RT(x_1ln(x_1)+x_2ln(x_2))
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Describe Δ_mix G
It is only affected by T and D, It is always negative (thus spontaneous), the minimum occurs when x_i = 0.5.
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What is Raoult's law ?
The activity of a component in a solution is equal to its mole fraction. It applies to all ideal solutions and it is ~ real solutions with only small amounts of components (when they are almost pure).
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Give the equation for Raoult's law
p_i =p*_i x_i
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What is the total pressure in the case of Raoult's law?
p_tot =p*_i x_i +p*_2 x_2
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Describe an ideal solution in terms of enthalpy
It has no enthalpic contribution.Δ_mix H = 0
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Describe a real solution in terms of enthalpy
It has an enthalpic contribution. Δ_mix H != 0
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What is Henry's law ?
The vapour pressure of a component in dilute solution is proportional to its concentration. It models behaviour that is charateristic of an ideal dilute solution. Real solutions follow the law when they are very dilute.
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Give the equation for Henry's law
p_i = K_H,i x_i
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Give the equation for the interaction parameter
β = zn_tot(2U_AB -U_AA-U_BB)/2 ] where z:coord number of species in solution; n_tot: total number of moles
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What is the interaction parameter?
It takes into account the difference in the internal energies U of bonds between different neighbours.
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Describe what β >0 means
The bonds between 1 and 2 are weaker so a 2 phase mixture may form.
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Describe what β =0 means
The solution is ideal Δ_mix H =0
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Describe what β<0 means
Bonds between 1 and 2 are stronger than 1 +1 and 2+2 (mixing is favoured)
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What is the critical solution temperature?
The temperature at which only 1 phase exists , below this two phases can exist.
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