a. Compute the standard enthalpy of vaporization of water at 340 K. You may assu

Question

a. Compute the standard enthalpy of vaporization of water at 340 K. You may assume that any relevant heat capacities are independent of temperature.

b. Compute the enthalpy of vaporization of water at 298.15 K and 100 bar.

You may assume water is ideal. You may also assume that the thermal expansion coefficient(eta) and the isothermal compressibility(kappa) of liquid water are independent of pressure. You may not assume that the molar volume of liquid water is independent of pressure. Take the molar volume of liquid water at 298.15 K and 1 bar to be 1.8 * 10^-5 m3/mol.

Explanation / Answer

SOLUTION:

(a) Find Delta Hvap(T2), which is
Delta Hvap(T1) + Delta Cp* (T2 - T1) where Delta Cp = Cg - Cl

where, Cg=molar heat capacity of gaseous water =33.6 J/(mol.K)

Cl=molar heat capacity of liquid water =75.3 J/(mol.K)

Delta Hvap(T1)=44.9KJ/mole, at T1=273K

Then ,

Delta Cp = (33.6 - 75.3) = -41.70 J/(mol K) or -0.0417 kJ/(mol K)

With -0.0417 kJ/(mol K)

Delta Hvap(T2)= 44.9 kJ/mol -0.0417 kJ/(mol K) * (273 - 340) = 47.69 kJ/mole answer   

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.