The molar volume of a certain solid is 142.0 cm3 mol−1 at 1.00 atm and 427.15 k, its melting temperature. the molar volume of the liquid at this temperature and pressure is 152.6 cm3 mol−1. at 1.2 mpa the melting temperature changes to 429.26 k. calculate the enthalpy and entropy of fusion of the solid

Respuesta :

Answer:

[tex]\Delta _{fus}H=3255.3J/mol[/tex]

[tex]\Delta _{fus}S=7.62\frac{J}{mol*K}[/tex]

Explanation:

Hello,

Clausius Clapeyron equation is suitable in this case, since it allows us to relate the P,T,V behavior along the described melting process and the associated energy change. Such equation is:

[tex]\frac{dp}{dT}=\frac{\Delta _{fus}H}{T\Delta _{fus}V}[/tex]

As both the enthalpy and volume do not change with neither the temperature nor the pressure for melting processes, its integration turns out:

[tex]p_2-p_1=\frac{\Delta _{fus}H}{\Delta _{fus}V}ln(\frac{T_2}{T_1} )[/tex]

Solving for the enthalpy of fusion we obtain:

[tex]\Delta _{fus}H=\frac{(p_2-p_1)(V_2-V1)}{ln(\frac{T_2}{T_1})} =\frac{(11.84atm-1.00 atm)(156.6cm^3/mol-142.0cm^3/mol)}{ln(\frac{429.26K}{427.15K} )} \\\\\Delta _{fus}H=32127.3atm*cm^3/mol*\frac{101325Pa}{1atm}*(\frac{1m}{100cm} )^3\\\Delta _{fus}H=3255.3J/mol[/tex]

Finally the entropy of fusion is given by:

[tex]\Delta _{fus}S=\frac{\Delta _{fus}H}{T_1} =\frac{3255.3J/mol}{427.15K}\\ \\\Delta _{fus}S=7.62\frac{J}{mol*K}[/tex]

Best regards.

We have that for the Question " calculate the enthalpy and entropy of fusion of the solid" it can be said that the enthalpy and entropy of fusion of the solid are

  • Sfus = 5.526 Pa.m^3/K.mol
  • dHfus= 2.366 kJ/mol  Respectively

From the question we are told

  • The molar volume of a certain solid is 142.0 cm3 mol−1 at 1.00 atm and 427.15 k, its melting temperature.
  • the molar volume of the liquid at this temperature and pressure is 152.6 cm3 mol−1. at 1.2 mpa the melting temperature changes to 429.26 k.
  • calculate the enthalpy and entropy of fusion of the solid

the enthalpy and entropy of fusion

Generally the equation for the Clausius-Claepyron equation:   is mathematically given as

[tex]\frac{dP}{dT}=\frac{dSfus}{dVfus}[/tex]


Where

Average temperature = 0.5(427.15+429.26) K

Average temperature = 428.205K

Therefore

[tex]dT = 2.11 K\\\\dVfus = 1.06*10-5 m^3/mol\\\\dSfus = 5.526 Pa.m^3/K.mol \\\\Where\\\\dSfus = \frac{dHfus}{average T}\\\\dHfus = 5.526 J/K.mol * 428.205 K\\\\[/tex]

  • dHfus= 2.366 kJ/mol

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