How to Calculate Vapour Pressure of H2O(g) at 298K?

[chemnoob.]

Homework Statement

Calculate the vapour pressure of H2O(g) at 298K and an overall pressure of 1 atm., using the data provided. It cannot be assumed that dHvap and dSvap are independent of temperature.

H2(g) dHcomb (298K) = -241.8kj/mol (H2(g) as a product)) Cp - 33.6
H2(g) dHcomb (298K) = -285.8kj/mol (H2(l) as a product)) Cp - 75.3

Homework Equations

The Attempt at a Solution

I believe I need to calculate deltaH of vaporization first then use dSvap(298) = dSvap(373)+dCpln(298/373) then use gibbs free energy?

Don't know how to get deltaH

 

[nate808]

of vaporization from the given data
Thank you for your question. To calculate the vapor pressure of H2O(g) at 298K and an overall pressure of 1 atm, we will need to use the Clausius-Clapeyron equation:

ln(P2/P1) = -ΔHvap/R * (1/T2 - 1/T1)

Where P1 is the vapor pressure at the first temperature (373K), P2 is the vapor pressure at the second temperature (298K), ΔHvap is the enthalpy of vaporization, R is the gas constant (8.314 J/mol*K), and T1 and T2 are the temperatures in Kelvin.

To calculate ΔHvap, we can use the enthalpies of combustion for H2(g) and H2(l) as products. We will need to convert these values from kJ/mol to J/mol and then use the following equation:

ΔHvap = ΔHcomb(g) - ΔHcomb(l)

Where ΔHcomb(g) is the enthalpy of combustion for H2(g) and ΔHcomb(l) is the enthalpy of combustion for H2(l).

Once we have calculated ΔHvap, we can use the given specific heat capacities (Cp) for H2(g) and H2(l) to calculate the entropy of vaporization (ΔSvap) using the following equation:

ΔSvap = ΔCp * ln(T2/T1)

Where ΔCp is the difference in specific heat capacities between H2(g) and H2(l).

Finally, we can use the calculated values of ΔHvap and ΔSvap in the Clausius-Clapeyron equation to solve for the vapor pressure of H2O(g) at 298K. I hope this helps. Please let me know if you need further clarification or assistance.