Problema 10 · Química II URV 2000

Problema 10. Termodinámica de la vaporización de agua

A sample containing 2.5 moles of liquid water at 100 °C (density $d = 0.96\text{ g}\cdot\text{mL}^{-1}$) is held inside a cylinder fitted with a frictionless movable piston.

The water undergoes complete vaporization against a constant external pressure of 1 atm. Assuming ideal gas behavior for water vapor, calculate:

Data:

Enthalpy of vaporization of water, $\Delta H_{\text{vap}} = Q_{\text{vap}}(\text{H}_2\text{O}) = 40.7\text{ kJ}\cdot\text{mol}^{-1}$; $R = 0.082\text{ atm}\cdot\text{L}\cdot\text{mol}^{-1}\cdot\text{K}^{-1}$; $1\text{ atm} = 101\,325\text{ Pa}$; molar mass of water $M = 18\text{ g/mol}$.

a.

The heat exchanged by the system, $Q$.

b.

The expansion work performed, $W$ (using the IUPAC sign convention $W = -P_{\text{ext}}\Delta V$).

c.

The change in internal energy of the process, $\Delta U$.