[gaseous_entity]

What combination or series of equations would allow me to estimate properties of linear n-alkane mixtures over the range 0C -> 100C?  Of particular interest are vapour pressure and critical point.

For example:

• 5% methane, 10% ethane, 85% propane
• 3% methane, 0% ethane, 97% propane
• 0% methane, 7% ethane, 93% propane

I'd like to start with just these three in various combinations; and I see how to make use of CC/Antoine for single alkanes, but I'm stuck on mixtures.

[Enthalpy]

+100°C is just above the critical temperature of propane so you can't find a vapour pressure there.

I can't tell whether 5% methane can dissolve in propane at 0°C but for sure, you can't deduce that from mixture proportions and vapour pressure, since 0°C is well above methane's critical temperature.