How to Calculate the Internal Energy Change in Temperature Followed by Change of State – Part 1

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 fusion (aka the (latent) heat of fusion) is the amount of energy (enthalpy/heat) that must be added to a solid substance to transform a quantity of that substance into a liquid, 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:

Assuming the water vapor to be a perfect gas, calculate the internal energy change when 1 mol of water at 100°C and 1 bar pressure is converted to ice at 0°C. Given standard ΔHfus of ice = 6.00 kJ mol-1 and the heat capacity of water is 4.2 J/(g°C).

Solution:



Click to enlarge the image

Cv = Heat capacity at constant volume, Δt = Change in temperature, ΔH = Change in enthalpy, ΔU = Change in internal energy, P = Pressure, ΔV = Change in volume

Feeling being dynamic❓ 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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