Tell us Gibbs free energy will change as the number of molecules change so good for dealing with open system

Also good as G not a good measure for the stabilty of systems where the amount of substances is changing

For 1 component in a system: U= G/n

For a multicomponent system: G= Sum of Ux n for all species in the system added together

G= Sum of chemical potential for all species in a system

For removal of reactant: Where Delta n is a negative number due to number of mole decreasing

G= U(reactants) x (Delta n Reactant)

Fpr adding products: Where delta n is a + number for to number of mole will go up

Delta G = U products x Delta n Reactant

The chemical potential for a compound in a particualr system is a measure of the free energy of a mole in the system

It is independent of system size

The total free energy of the system can be found by adding together the chemical potentials multiplied by amount of all component in moles

In a solution or mixture there are net forces between the molecules unlike an ideal gas

The molecules all interact with identical magnitudes and distance dependencies so they all attract and repel equally and molecules cant tell each other apart

The enthalpy of mixing components is 0 and volume is simply adding the volumes of all solutes in the solution

PV=nRT

Ideal is defiend as hypothetical gas whose molecules occupy neglible space and 0 interactions

U = U(standard state) + RT x ln(p/p in standard state

Ux = Ux standard state + RT x ln( pressure of x / pressure in standard state

When mix a defined volume of pure liquids and the volume is not sume of the volumes you added together

If temperature increase or decrease when you mix the 2 liquids, as the entahlpy change wont be zero when mixed

So these are non ideal solutions

Raoults Law will relate pafrtial vapour pressure of the individual component of their compostion

Px = Nx x Px standard state

Px = Sum of Nx x Px standard state

The vapour pressure of a component in the solution is equal to the mole fraction that component multiplied by vapour pressure for pure component

Partial vapour pressure is the sume of mole fraction of the component x their partial vapour pressure

The molecules in the solution do not intercat with each other identically so the behaviour of a given molecule depend on composition of the solution

It is non-random and there is direct consequence that therw are differeing interactions between different molecule types

2 molecules that attract each other strongly will be located closer together than weaker attracted molecules, and 2 molecules that reple each other will be further apart that predicted by random distribution

Chemical potential of x = Ux + RT x ln[X]

The equation is a straight line where y=mx+c

Ux = C

RT= m

Ln[x] = x

They de niot interact identically with eachy other and is a non random distribution as molecules that are attracted to each other are closer togther than random distribution predict and molecules that repel are further away than predicted by random distribution

Ux = Ux + RT Ln(Y[X])

Y= activuty coefficient and is calcualted as effective concentration/actual concentration

Use U=Ux + RTLn(X) to work out concentration that give same chemical potential as real solution

If Y= 1 then it is an ideal solution

If Y is greater than 1 then solution is less stable than predicted

If Y is less then 1 then solution is more stable than predicted

Ideal will obey Raoults law and non ideal + and - will not

For ideal the Delta H = 0 and volume is sum of all componemts

For + non ideal then heat is absrobed and volume is greater than component sum

For - non ideal then heat is released and volume is less than component sum

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These are non ideal solutions made of ions in water for NaCl in water the ions are broken up and released so Na+ and Cl-, these will then disrupt the water -water hydrogen bonds due to hydrogen shells form round the ions that allow electrostatic interaction between charged ions and the partial wayter charges

They have strong intercations between ions and water and dont start non ideal behavioiur at low temperatures

For enthalpy = Ion-Water electrostatic intercations compensate for loss of water -wayer hydrogen bonding so enthalpy change is -

For entropy= Watrer are held in particualor arrange,enmt so less microstates at some overall energy so additon of ion lead to lower entropy

Samlle the ion the bigger the change

As concentration increases as does the average distance between ions due to stronger attraction or repulsion

This will cause non-rando, ion distribuiton as ions are surrounded by opposite charged ones

Lower chemical potential so are more stable

Quantitative way to calculate solute-solute electrosyatic interactions in ionic solutions

Ionic strength = 1/2 Sum of [C]Z 2

C= concentration and is charge

For multiple ions:

LogYxy= -A/ZxZy/ I^1/2

At low salt concentration there is greater protein solubility so more of the protein will be held in suspension

At higher salt concentration the protein drop out of suspension and will precipitate and this happens at different times for each protein

Folded protein state is more stable in water compared to the unfolded state but in presence of high ion concentratin is is more orderded at lower ion concentration

This means more protein unfolding as ion concentration increases