4. Thermodynamic data for C (graphite) and C( diamond ) at 298 K is given in the

Question

4. Thermodynamic data for C(graphite) and C(diamond) at 298 K is given in the table below.

2.377

a) Calculate delta Ho and delta So and delta Go for the transformation of 1 mole of graphite to diamond at 298 K.

b) Is there a tempature at which this transformation will occur spontaneously at atmospheric pressure? Justify your answer.

8. Methanol can be made using the Fischer-Tropsch process according to the reaction CO (g) + 2 H2 (g) <----> CH3OH (g).

a) Calculate the entropy change for the reaction at 25o.

b) Calculate the value of the equilibrium constant K at 25o C.

c) What is the equilibrium partial pressure of methonal (CH3OH (g)) in the above reaction, if the inital partial pressures are PCO = 1 atm and P(CH3OH) = 0.5 atm?

2.377

Explanation / Answer

4)

a)
Ho = Hfo C(diamond) - Hfo C(graphite)
= 1.895 -0
= 1.895 KJ/mol
= 1995 J/mol

So = Sfo C(diamond) - Sfo C(graphite)
= 2.377 -5.740
= -3.363 J/mol-K

Go = Ho - T*So
= 1995 - 298*(-3.363)
= 2997 J/mol
= 2.997 KJ/mol

b)
Go = Ho - T*So
for reaction to be spontaneous,
Go < 0
SO,
Ho - T*So < 0
1995 - T*(-3.363) <0
1995 + 3.363*T <0
for this to happen T must be negative
so it is not possible

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