How to Calculate the Internal Energy Change of Evaporation

In thermodynamics the reference is the internal energy (in chemistry).


The internal energy of a thermodynamic system is the energy of the system as a state function, measured as the amount of energy required to bring the system from its standard internal state to its internal state of interest.

The enthalpy of vaporization (aka the (latent) heat of vaporization/evaporation) is the amount of energy (enthalpy/heat) that must be added to a liquid substance to transform a quantity of that substance into a gas/vapor, and a function of the pressure and temperature at which the transformation occurs.

Latent heat (aka latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.

Question:

A swimmer coming out from a pool is covered with a film of water weighing about 18 g. How much heat must be supplied to evaporate this water at 298 K & 1 bar? Calculate the internal energy of vaporization at 298 K assuming water vapor to be a perfect gas. Enthalpy of vaporization for water at 298 K = 44.01 kJ mol–1.

Solution:



Click to enlarge the image

ΔU = Change in internal energy, Î”H = Change in enthalpy, Î”ng = Change in moles of gaseous molecules, R = Universal gas constant, T = Absolute temperature

Change in your internal energy now❓ Let Chemaficionado know at mychemistryhomework@gmail.com❗

References:
(1)    Wikipedia Contributors. Laws of thermodynamics. Wikipedia. https://en.wikipedia.org/wiki/Laws_of_thermodynamics.

(2)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

(3)    Internal energy. Wikipedia. https://en.wikipedia.org/wiki/Internal_energy

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