Week 4 - Osmometry and Ion Selective Electrodes

Question 1

How does an Osmometer work

Answer 1

• sample is supercooled (below freezing point)
• freeze pulse/physical shock causes sample to crystallize (seeding)
  -> heat of fusion (ice water mix) raises temp to plateau
  Plateau temp is used to calculate concentration

Question 2

Sample Freezing Point UNITS

Answer 2

mOsm/Kg

Question 3

Osmole

Answer 3

Amount of substance dissociated to produce 1 mole particles in a solution
glucose - one (doesnt break apart)
NaCl - two

Question 4

Osmolarity

Answer 4

Concentration of a solution expressed as # particles / L H20

Question 5

Osmolality

Answer 5

Concentration of solution expressed as the # of particles / kg
Clinical setting - not temp dependent

Question 6

Colligative Properties

Answer 6

Solution properties that depend on # particles/volume solvent

1. DEC freezing point *
2. INC boiling point *
3. INC osmotic pressure
4. DEC vapour pressure

Question 7

Calculate FPD

Answer 7

unknown mOsm/kg = 1000 mOsm/kg x unknown freezing point (°C) / -1.86 °C

Question 8

Calculate Osmolality

Answer 8

2[Na+] + glucose + urea mOsm/kg (mmol/kg)