Section: Chemical and Physical Foundations of Biological Systems

27) If a gas occupies 0.1L at 200atm, what will its volume be at 1atm?

1. slightly less than 20L
2. 20L
3. slightly more than 20L
4. 2000L

Ideal gases undergoing pressure and volume changes are related by the expression P₁V₁/T1=P₂V₂/T₂. Here, temperature is not involved and P₁V₁= P₂V₂. However, since P₁ is greater than 10atm, the size of the molecules cannot be ignored and volume V₁ is slightly greater than it should be for an ideal gas. Therefore, the calculated volume V₂=20L is slightly larger than it should be.
Choice a) is correct.
a) slightly less than 20L, correct.
b) 20L, incorrect, The initial volume at a pressure of 200atm includes a small contribution from the molecules themselves, and therefore the initial volume of 0.1L is larger than the volume of an ideal gas.
c) slightly more than 20L, incorrect, See explanations for a) and b).
d) 2000L, incorrect, This answer choice incorrectly divides the initial pressure by the initial volume.