Equilibria of HN3: Find Vapor Pressure, Enthalpy & Entropy

[physicsss]

The vapor pressure of HN3 is 58 Torr at -22.75 C and 512 Torr at 25C. Find the standard enthalpy of vaporization, standard entropy of vaporization, the standard free energy of vaporization.

I know how to find the first two, but for some reason I can't find the third one...Is the equation for it lnP=-G/(RT). If so, what unit is P in and which P should I use and is R 8.3145 and what temperature do I use?

 

[gravenewworld]

did you try G=H-TS?

 

[ravenprp]

To find the standard free energy of vaporization, you can use the equation ΔG = ΔH - TΔS, where ΔH is the standard enthalpy of vaporization and ΔS is the standard entropy of vaporization.

To find ΔH, you can use the Clausius-Clapeyron equation: ln(P2/P1) = -ΔH/R * (1/T2 - 1/T1), where P1 and T1 represent the vapor pressure and temperature at one point, and P2 and T2 represent the vapor pressure and temperature at another point. In this case, you would use the values of 58 Torr and -22.75 C for P1 and T1, and 512 Torr and 25 C for P2 and T2.

To find ΔS, you can use the equation ΔS = (ΔH/T) - Rln(P2/P1). Again, you would use the same values for P1, T1, P2, and T2 as mentioned above.

Once you have both ΔH and ΔS, you can plug them into the equation ΔG = ΔH - TΔS, using a temperature of your choice (usually the standard temperature of 25 C is used).

Note that the units for pressure in these equations should be in Pa, and the gas constant R is indeed 8.3145 J/mol K.