Freezing Point Depression Flashcards
Define vapour pressure
The pressure of the vapour above the liquid when liquid and vapour are at equilibrium
Higher boiling points means lower vapour pressure?
YES
lower boiling points means higher vapour pressure? YES OR NO
YES
What does the Raoults law tell us?
The total pressure from all the molecules in the gas/vapour phase
Write the Raoults Law
P (total) in mm Hg = X(A) P(A) + X (B) X (B)
What does X and P symbolise in the Raoult’s Law?
X = MOLE FRACTION (e.g. mole/total moles)
P = Vapour pressure
What does A and B symbolise in the Raoult’s Law?
Liquids A and B
Units of Vapour Pressure?
mm Hg (millimetres of mercury)
Include terms: hydrogen bonding, energy, boiling point
What happens if theres 2 polar molecules in the solution?
What happens to the partial vapour pressure and total vapour pressure?
Provide an example
- More hydrogen bonding and so will keep them in the liquid phase.
- More energy required to break them = higher boiling point = lower vapour pressure
- Partial VP decreases for both molecules and THUS the total VP also decreases
- water and ammonia
What happens if theres 1 polar and 1 non-polar molecules in the solution?
What happens to the partial vapour pressure and total vapour pressure?
Provide an example
- Repulsion will occur and they will try to escape to the gaseous phase = higher vapour pressure
Partial VP increases and total VP increases
H20 and hexanol
How many equations are there for Freezing Point Depression?
2 equations:
1. no excipients
2. with excipients
Write down the equation that is associated with ‘no excipients’ and only DRUG
C (iso) = 0.52/FD 1%
Write down the equation that is associated with ‘excipients’ and DRUG
w = 0.52 - a / b
w = conc. needed of adjusting material
a = FD 1% of the drugs solution at its current concentration
b = The FD 1% of adjusting material
