[orgo814]

I am studying for ACS Physical Chemistry exam and attached is a picture of a question with answer I do not understand. Particularly, I am confused about what the picture is showing and why in their explanation they are referring to volume when the figure shows decreasing mass

Thank you

[mjc123]

The picture shows a descending mass, not a decreasing mass. (It is not a bar graph, if that's what you were thinking.) There appears to be a gas in the bottom section of a container with a moveable partition, with a mass on top of the partition, which moves downward under gravity until the force is balanced by the pressure of the gas. (There is a vacuum in the upper compartment, so we don't have a decrease of pressure there to worry about.)

[orgo814]

That makes sense. Thank you. I wish they described the figure a little more in the problem..