Question 10.4: CALCULATING AN ENTROPY OF VAPORIZATION The boiling point of ...

CALCULATING AN ENTROPY OF VAPORIZATION

The boiling point of water is 100 °C, and the enthalpy change for the conversion of water to steam is $ΔH_{vap}$ = 40.67 kJ/mol. What is the entropy change for vaporization, $ΔS_{vap}$ , in J/(K · mol)?

STRATEGY
At the temperature where a phase change occurs, the two phases coexist in equilibrium and ΔG , the free-energy difference between the phases, is zero: ΔG = ΔH − TΔS = 0.

Rearranging this equation gives ΔS = ΔH/T , where both ΔH and T are known.
Remember that T must be expressed in kelvin.

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