Question

14.

What is ΔGo (in kJ) at 19 ºC for the phase change of nitromethane from the liquid to the gaseous state?

CH3NO2(l) → CH3NO2(g)

CH3NO2(l): ΔHfo = -113.1 kJ/mol and So = 171.8 J/K mol)
CH3NO2(g): ΔHfo = -74.7 kJ/mol and So = 274.4 J/K mol)​

Answer 1

we have:

Hof(CH3NBO2(l)) = -113.1 KJ/mol

Hof(CH3NO2(g)) = -74.7 KJ/mol

we have the Balanced chemical equation as:

CH3NBO2(l) ---> CH3NO2(g)

deltaHo rxn = 1*Hof(CH3NO2(g)) - 1*Hof( CH3NBO2(l))

deltaHo rxn = 1*(-74.7) - 1*(-113.1)

deltaHo rxn = 38.4 KJ/mol

we have:

Sof(CH3NBO2(l)) = 171.8 J/mol.K

Sof(CH3NO2(g)) = 274.4 J/mol.K

we have the Balanced chemical equation as:

CH3NBO2(l) ---> CH3NO2(g)

deltaSo rxn = 1*Sof(CH3NO2(g)) - 1*Sof( CH3NBO2(l))

deltaSo rxn = 1*(274.4) - 1*(171.8)

deltaSo rxn = 102.6 J/mol.K

WE HAVE:

deltaH = 38.4 KJ/mol

deltaS = 102.6J/mol.K

= 0.1026 KJ/mol.K

T= 19.0 oC

= (19.0+273) K

= 292 K

we have below equation to be used:

deltaG = deltaH - T*deltaS

deltaG = 38.4 - 292.0 * 0.1026

deltaG = 8.44 KJ/mol

Answer: 8.44 KJ/mol