Consider the following data for compound A:
(delta)Hf(kj/mol) S(J/K*mol)
A(s) -224.57 32.36
A(l) -172.45 109.55
Use these data to determine the normal freezing point of compound A. Report your answer to 3 significant figures and degrees Celsius)
Freezing point =
we have the Balanced chemical equation as:
A(s) ---> A(l)
we have:
Hof(A(s)) = -224.57 KJ/mol
Hof(A(l)) = -172.45 KJ/mol
deltaHo rxn = 1*Hof(A(l)) - 1*Hof( A(s))
deltaHo rxn = 1*(-172.45) - 1*(-224.57)
deltaHo rxn = 52.12 KJ/mol
we have:
Sof(A(s)) = 32.36 J/mol.K
Sof(A(l)) = 109.55 J/mol.K
we have the Balanced chemical equation as:
A(s) ---> A(l)
deltaSo rxn = 1*Sof(A(l)) - 1*Sof( A(s))
deltaSo rxn = 1*(109.55) - 1*(32.36)
deltaSo rxn = 77.19 J/mol.K
deltaSo rxn = 0.07719 KJ/mol.K
FOR EQUILIBRIUM:
deltaGo rxn = 0
we have below equation to be used:
deltaGO = deltaHO - T*deltaSO
0.0 = 52.12 - T *0.07719
T = 675 K
= (675 - 273) oC
= 402 oC
Answer: 402 oC
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