Ideal and non ideal solutions -Chemistry of life
What is the chemical potential
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
What is the equation of chemicla potential
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
How does G change when add or remove reactants and product
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
What is chemial potential rules
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
What are Ideal solutions
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
What is the ideal gas equation
PV=nRT
Ideal is defiend as hypothetical gas whose molecules occupy neglible space and 0 interactions
What is the chemical potential for an ideal gas
U = U(standard state) + RT x ln(p/p in standard state
What is the chemical potential for each component of a mixture
Ux = Ux standard state + RT x ln( pressure of x / pressure in standard state
What are deviation from ideal solution rules
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
What equation can define ideal solutions
Raoults Law will relate pafrtial vapour pressure of the individual component of their compostion
Px = Nx x Px standard state
If there are more than 1 component in the mixture for raoults law
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
What is a non-ideal solution
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
What is the atom distribution in a non ideal 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
What is the thermodynamics of ideal solutions
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
How do non ideal solution molecules intercat
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
What is the chemical potential for Non ideal Solutions
Ux = Ux + RT Ln(Y[X])
Y= activuty coefficient and is calcualted as effective concentration/actual concentration
What is the effective concentration
Use U=Ux + RTLn(X) to work out concentration that give same chemical potential as real solution
What does the Activity coefficent mean
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
What are thye differences between ideal and non ideal solutions
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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What are ionic solutions
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
What are Dilute ionic solutions
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
What are concentrated ionic solutions
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
What is the Debye-Huckel theory
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
What is the protein solubility
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
What is folding entropy
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