A sealed, perfectly insulated container is divided into two equal compartments by a…

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

A sealed, perfectly insulated container is divided into two equal compartments by a thin removable partition. Initially, the left compartment contains

1.00\,\text{mol}

of liquid benzene at its normal boiling point (

80.1\,^\circ\text{C}

), and the right compartment contains

1.00\,\text{mol}

of benzene vapor at

80.1\,^\circ\text{C}

and

1.00\,\text{atm}

. The molar enthalpy of vaporization of benzene at this temperature is

30.7\,\text{kJ}\,\text{mol}^{-1}

. The partition is suddenly removed, and the system is allowed to reach equilibrium at

80.1\,^\circ\text{C}

with no heat exchanged with the surroundings. (a) Predict and justify the final vapor fraction. (b) Calculate the net heat of the phase change that occurs inside the container while the system moves toward equilibrium. (c) Explain why the temperature of the benzene remains constant at

80.1\,^\circ\text{C}

throughout the process even though heat is generated or absorbed internally.

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