8. Gas mixtures: partial pressure, volume %. The composition of the air. Dissolution of gases in liq- uids, Henry's law, the decompression sickness

Question 1

What is Solubility?

Answer 1

The ability of a substance (solute) to dissolve in a given solvent at given conditions (temperature, pressure, pH). It is measured as the saturation concentration (M).

Question 2

How can endothermic solution be affected by temperature?

Answer 2

Endothermic solution is favored by high temperature

Question 3

How can the solubility of exothermic solution be affected by temperature?

Answer 3

Endothermic solution is favored by high temperature

Question 4

How can the solubility of the solution that is neither endo- nor exothermic be affected by temperature?

Answer 4

Endothermic solution is favored by high temperature

Question 5

State Henry’s law

Answer 5

Solubility of gases in liquids is directly proportional to their partial pressure.

c = kP
(concentration = solubility constant x partial pressure)

k is the Henry’s law constant (M/atm), which must be determined experimentally for each combination of gas, solvent and temperature.

Question 6

Give the formula representing Henry’s law

Answer 6

c= k xp
concentration = solubility constant x partial pressure

Question 7

Describe the relationship between gas solubility and temperature

Answer 7

The solubility of gases in liquids is inversely proportional to temperature

→ Solution of gases is always exothermic (no interactions to break).

→ Solution of gases is favored by low temperature.

Question 8

What is The Bunsen coefficient?

Answer 8

Volume of gas in liter dissolved in 1 liter solvent (t = 0 °C, p = 105 Pa)

(The solubility of gases in liquids is inversely proportional to temperature)

Question 9

3 examples of medical importance of gas solubility in liquid

Answer 9

1. Hyperbar-oxygen therapy
2. Decompression sickness
3. Plasma pH regulation

Question 10

How can Henry’s law be related to diving?

Answer 10

The amount (concentration) of dissolved nitrogen in bodily fluids changes with depth in water.

Question 11

Describe Decompression sickness based on Henry’s law

Answer 11

Nitrogen moves from high pressure in the lungs into the blood (low pressure)

2 cases can happen

1. A slow return to the surface → nitrogen returns to the lung where it is breathed out
2. A very quick return → not enough time for nitrogen to leave the blood → forming painful bubbles → DECOMPRESSION SICKNESS

Question 12

Formula for the carbonic acid/bicarbonate buffer system

Answer 12