Colligative Properties

?
  • Created by: LBCW0502
  • Created on: 28-02-18 14:04
What are colligative properties?
Properties that depend on the relative numbers of solute and solvent molecules and not on the chemical identity of the solute
1 of 24
What does colligative mean?
Bound together in a collection
2 of 24
Give examples of colligative properties in everyday life
Salt placed on paths, lucozade turning urine dark yellow, antifreeze
3 of 24
Give examples of colligative properties in pharmaceutical sciences
Renal dialysis, water content in homeostasis, HFA MDIs QVAR and ventolin
4 of 24
What are the four colligative properties?
Lower vapour pressure of solution, higher boiling point of solution, lower freezing point of solution, osmosis occurs
5 of 24
Describe features of lowering vapour pressure
Liquid in closed container in equilibrium with vapour. Amount of pressure exerted in close system by vapour (vapour pressure). Vapour pressure of pure solvent and solution are different
6 of 24
Does a solute have its own pressure vapour?
No
7 of 24
Does a solution have its own vapour pressure?
Yes - lower vapour pressure
8 of 24
What is Raoult's law?
Vapour pressure of solution is equal to the vapour pressure of solvent at the same temperature multiplied by the mole fraction of the solvent in the solution
9 of 24
Raoult's law is only obeyed in which type of solutions?
Ideal solutions e.g. solvent-solute interactions = solvent-solvent and solute-solute interactions (obeys law at all mole fractions)
10 of 24
What does a positive deviation from Raoult's law mean?
Solute-solvent interactions < solvent-solvent interactions
11 of 24
What does a negative deviation from Raoult's law mean?
Solute-solvent interactions > solvent-solvent interactions e.g. phenol and water (outside of curve)
12 of 24
Describe phase transition graphs
More Gibbs free energy/more negative value, three phases, delta H - T delta S = delta G
13 of 24
Why is the vapour pressure of a solution lowered?
More Gibbs free energy, enthalpy (+) requires energy to vaporise, entropy (+) more disorder in vapour. Enthalpy of solvent and solution similar (same forces in ideal solution)
14 of 24
Describe features of boiling point elevation
Non-volatile solute (e.g. NaCl added to solvent/water) lowering vapour pressure causes elevation of boiling point. Entropy of solvent. Below b.p liquid phase favoured. Above b.p vapour phase favoured. Non-volatile solute lowers free energy
15 of 24
Why does boiling point elevation take place?
When entropy increases, the minimum free energy is reduced. When comparing solution to pure solvent, the solution has a lower free energy (more disorder), leading to a higher b.p. (point at which it forms a vapour) - refer to graphs and formula
16 of 24
Describe features of freezing point depression
Non-volatile solute added to solvent (NaCl to water) lowering vapour pressure and causes depression of melting point. Above f.p. of liquid phase favoured, below f.p. of solid phase favoured. Adding non-volatile solute to solvent decreases free energy
17 of 24
Why does vapour pressure lower with freezing point?
Solution has lower free energy than solvent and solid, leading to a lower f.p. - increase in entropy of solution/lower free energy (more stable) - refer to graphs and formula
18 of 24
What is the calculation for vapour pressure lowering?
Freezing - point depression = freezing point constant x molality (van't Hoff factor used experimentally if solution is ionic/ion pairs)
19 of 24
Describe features of osmosis
Flow of solvent through membrane into more concentrated solution. Thermodynamic property. Lowers free energy of solution. Pure solvent has tendency to push into solution.
20 of 24
How is the osmotic pressure calculated?
Molar concentration of solute x gas constant x temperature (in Kelvin)
21 of 24
What are the uses of the colligative property, freezing point depression?
Salt put on winter roads, ethylene/propylene glycol, car cooling system
22 of 24
What are the uses of the colligative property, osmosis?
Dialysis, water homeostasis
23 of 24
What are the uses of the colligative property, vapour pressure lowering?
Raoult's law, effect of ethanol
24 of 24

Other cards in this set

Card 2

Front

What does colligative mean?

Back

Bound together in a collection

Card 3

Front

Give examples of colligative properties in everyday life

Back

Preview of the front of card 3

Card 4

Front

Give examples of colligative properties in pharmaceutical sciences

Back

Preview of the front of card 4

Card 5

Front

What are the four colligative properties?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Pharmacy resources:

See all Pharmacy resources »See all Colligative Properties resources »