Certified Hyperbaric Technologist Test CHT Hyperbaric Physics and Gas Laws 3 — Questions and Answers
Question 1: Graham's Law of diffusion states that the rate of gas diffusion is inversely proportional to what?
- The gas temperature
- The square root of its molecular weight (Correct answer)
- Its partial pressure
- Its solubility coefficient
Correct answer: The square root of its molecular weight
Graham's Law: diffusion rate is inversely proportional to the square root of molecular weight, so lighter gases diffuse faster.
Question 2: Why does a middle-ear squeeze most commonly occur during chamber compression (descent)?
- Gas in the middle ear expands
- Gas in the middle ear is compressed, creating a relative vacuum (Correct answer)
- Oxygen dissolves into the eardrum
- Temperature drops in the ear canal
Correct answer: Gas in the middle ear is compressed, creating a relative vacuum
During compression, increasing pressure compresses middle-ear gas (Boyle's Law), creating a relative vacuum that pulls the eardrum inward.
Question 3: Which gas law explains decompression sickness when bubbles form during ascent?
- Charles's Law
- Henry's Law (Correct answer)
- Dalton's Law
- Gay-Lussac's Law
Correct answer: Henry's Law
Henry's Law explains that as ambient pressure drops, dissolved inert gas comes out of solution and can form bubbles.
Question 4: A gas occupies 4 L at 1 ATA. At what pressure will it occupy 1 L at constant temperature?
- 2 ATA
- 3 ATA
- 4 ATA (Correct answer)
- 8 ATA
Correct answer: 4 ATA
By Boyle's Law, P2 = (P1V1)/V2 = (1 x 4)/1 = 4 ATA.
Question 5: What term describes the actual pressure exerted by a single gas within a mixture?
- Absolute pressure
- Partial pressure (Correct answer)
- Gauge pressure
- Vapor pressure
Correct answer: Partial pressure
Partial pressure is the pressure one component gas contributes to the total mixture.
Question 6: Charles's Law describes the relationship between which two variables at constant pressure?
- Volume and temperature (Correct answer)
- Pressure and volume
- Pressure and temperature
- Solubility and pressure
Correct answer: Volume and temperature
Charles's Law states that gas volume is directly proportional to absolute temperature at constant pressure.
Question 7: One atmosphere absolute (1 ATA) is approximately equal to how many millimeters of mercury?
- 260 mmHg
- 500 mmHg
- 760 mmHg (Correct answer)
- 1013 mmHg
Correct answer: 760 mmHg
Standard atmospheric pressure is 760 mmHg (also 1013 mbar).
Certified Hyperbaric Technologist Test CHT Hyperbaric Physics and Gas Laws 3
Graham's Law of diffusion states that the rate of gas diffusion is inversely proportional to what?