Assume that you have a liquid in a cylinder equipped with a movable piston. There is no air in the cylinder, the volume of space above the liquid is 200 mL, and the equilibrium vapor pressure above the liquid is 28.0 mm Hg. What is the equilibrium pressure above the liquid when the volume of space is decreased from 200 mL to 100 mL at constant temperature?

Video transcript

Hi everyone for this problem. It reads determined the resulting equilibrium pressure above the liquid in a cylinder equipped with a movable piston. When the volume of space above the liquid decreases from ml to 200 ml at constant temperature, There is no air inside the cylinder and the equilibrium vapor pressure above the liquid is 40 of mercury. So the question that we want to answer here is the resulting equilibrium pressure. And what we're told in the problem is that the volume of space decreases from 400 ml to 200 ml at constant temperature. Okay, so we need a relationship between volume and this resulting equilibrium pressure. Alright, so the one thing we can note here is that vapor pressure does not depend on volume. So if vapor pressure does not depend on volume, that means the resulting equilibrium vapor pressure is still of mercury even after decreasing the volume. And that is because like we just said, Vapor pressure does not depend on volume, it depends on temperature. In the case of this problem, the temperature is constant. So the equilibrium pressure will not be affected equilibrium will just be reestablished if the volume is varied. So the answer for this problem is going to be of mercury, it's going to still be 40 of mercury even after decreasing the volume. Okay, so that is going to be the answer to this problem and that is the end of this problem. I hope this was helpful