Question

1 kg of saturated liquid water in a piston/cylinder assembly is at a pressure of 446.136 kpa. heat is added until half of the mass of liquid is converted to vapor, but the temperature remains constant. how much work does the piston do on the surroundings? (answer in units of kj.)

Answer 1

The work done by the piston on the surroundings is 1216.3 kJ.

How can you solve the work done by the piston on the surroundings?

Since half of the mass of liquid is converted to vapor, the mass of vapor is:

Mass of vapor = 0.5 * Mass of liquid water = 0.5 * 1 kg = 0.5 kg

The work done by the piston is equal to the heat added to the system. At constant temperature, the heat added is equal to the enthalpy change of the system. The enthalpy change is given by:

Enthalpy change = Mass of vapor * Specific enthalpy of vaporization

Plugging in the values, we get:

Enthalpy change = 0.5 kg * 2432.6 kJ/kg = 1216.3 kJ

Therefore, the work done by the piston on the surroundings is 1216.3 kJ.