Lecture 8 Formulas

Question 1

Diffusion Basics

Answer 1

dM/dt = Vdot x C

Rate of change of mass over rate of change of time equals flow of volume times concentration

Question 2

Fick’s Law

Answer 2

Rate of diffusion of a substance across an area is proportional to the concentration gradient
dM/dt proportional to dC/dx

Question 3

Fick’s Law pressure extrapolation

Answer 3

dM/dt is proportional to dP/dx

the rate of change of mass over time is directly proportional to the pressure gradient

Question 4

Solubility affects on concentration gradient, and therefore rate of diffusion

Answer 4

The greater the solubility of the gas in the liquid, the greater will be the concentration gradient between the surface layer of the liquid and its deeper layers; hence a more soluble gas diffuses into the deeper layers of the liquid more rapidly

Question 5

CO2 vs O2 diffusion

Answer 5

CO2 diffuses much faster (0.1s) than O2 (0.375s). This means patients with disease of the membrane have a problem with oxygenation, not removing CO2

Question 6

Graham’s Law

Answer 6

The rate of diffusion of gas is inversely proportional to the square root of it’s molecular weight.
D (dM/dt) is proportional to 1/(GMW)^0.5
D (dM/dt) is proportional to 1/(density)^0.5

Question 7

Osmotic Pressure with relation to avogadro’s hypothesis

Answer 7

An osmotic pressure of 101.325 kpa is produced when 1 mol of solute is dissolved in 22.4 liters of solution at 0C

Question 8

Molarity

Answer 8

Moles of solute/liters of solution

Question 9

Molality

Answer 9

Moles of solute/kilogram of solvent

Question 10

Normal Saline

Answer 10

0.9% NaCl

154 mmole/L

Question 11

0.9% saline vs 5% glucose

Answer 11

9g NaCl in 1L. 9/58 = 0.15 molar solution
Because NaCl ionizes, it exerts osmotic pressure double the molarity of NaCl (0.15 Na+ and 0.15 Cl-)
50g glucose in 1L. 50/180 = 0.3 molar solution

Question 12

Ringer’s Lactate

Answer 12

Sodium 131 mmol/L
Potassium 5 mmol/L
Calcium 2 mmol/L
*Lactate 29 mmol/L
Chloride 111 mmol/L
Total Osmolarity 278 mosmol/L
*assuming lactate completely ionized

Question 13

Capillary fluid balance

Answer 13

Net outward pressure of 13mmHg in arterial side
Net inward pressure of 7mmHg in venous side
Lymphatic system takes up 6mmHg of net outflow.

Question 14

Urine Osmolarity

Answer 14

Urine is 1000 mosmol/L

Question 15

Kidney Function

Answer 15

Osmotic pressure of the blood colloids is 4kPa (30mmHg) and it is known that a pressure of 4-5.3kPa (30-40 mmHg) is required to overcome the resistance of the kidney tubules and the rest of the urinary tract. A blood pressure above 9.3kPa (70mmHg) is therefore required for efficient kidney function.

Question 16

Pulmonary Edema

Answer 16

The difference between the capillary blood pressure and the subatmospheric pressure in the alveoli is less than the osmotic pressure exerted by the colloids in the capillaries, hence no liquid exudes into the alveoli.
Once negative pressure and blood pressure become higher than the osmotic pressure of the colloids, pulmonary edema occurs

Question 17

Raoult’s Law

Answer 17

Depression or lowering of vapor pressure of a solvent is proportional to the molar concentration of the solute.