Question

a. The standard enthalpy of vaporization of an inorganic
compound is 38.9 kJ/mol. If the temperature at which this phase
change occurs is 221.72 °C, determine ΔS°_{vap} (in
J/mol/K) for this compound. Report your answer to three significant
figures.

b. The entropy of freezing of an organic compound is -21.0
J/mol/K. If ΔH°_{freez} is -14.01 kJ/mol, determine the
temperature (in K) at which this phase change occurs. Report your
answer to two decimal places

Answer #1

(a). Standard enthalpy of vaporization, H^{o}_{vap}
= 38.9 kJ/mol

= 38900 J/mol

Temperature = 221.72 oC = 494.87 K

S^{o}_{vap}
= H^{o}_{vap}
/ T

= 38900 / 494.87

**S ^{o}_{vap}
= 78.6 J/mol.K**

(b). S^{o}_{fus}
= - 21.0 J/mol.K

H^{o}_{fus}
= -14.01 kJ/mol = - 14010 J/mol

S^{o}_{fus}
= H^{o}_{fus}
/ T

T = - 14010 / - 21

= 667.14 K

**Temperature = 667.14 K**

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The enthalpy of vaporization of methanol is 35.27 kJ/ mol at
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he thermodynamic properties for a reaction are related by the
equation that defines the standard free energy, ΔG∘, in
kJ/mol:
ΔG∘=ΔH∘−TΔS∘
where ΔH∘ is the standard enthalpy change in kJ/mol and
ΔS∘ is the standard entropy change in J/(mol⋅K). A good
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