Answer: The mole fraction of hydrogen gas at 20°C is 0.975
Explanation:
The information provided includes:
Water vapor pressure at 20°C is 17.5 torr
Total pressure at 20°C = 700.0 torr
Hydrogen gas vapor pressure at 20°C = (700.0 - 17.5) torr = 682.5 torr
To find hydrogen gas's mole fraction at 20°C, we utilize Raoult's law, represented by:

where,
= pressure of hydrogen gas = 682.5 torr
= total pressure = 700.0 torr
= mole fraction of hydrogen gas =?
Substituting the values into the equation yields:

Thus, the mole fraction of hydrogen gas at 20°C equals 0.975
I think the state change illustrated in the diagram is deposition.
Deposition is the transformation of gases into solids without transitioning through a liquid phase. It is the reverse process of sublimation.
A key distinction between gases and solids lies in the spacing of molecules; gases have large spaces between molecules, whereas solids have very minimal spacing, resulting in solids being more densely packed. This is illustrated in the diagram showing the transition from gases to solids.