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# Absolute entropy, free energy and spontaneity

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1) Describe in detail the difference in absolute entropy values for the following pairs:
a) C(s, graphite) and C(s, diamond)
b) HCl(g) and HCl(aq)
c) CH4(g) and CH3CH2CH2CH3(g)

2)
a) Calculate the values of DeltaHÂ° and DeltaSÂ° for the following reaction at 25Â°C.
b) Use the values from a to calculate DeltaGÂ° for the following reaction at 25Â°C.
c) Explain fully whether this reaction spontaneous or non-spontaneous at 25Â°C?

2 CH3OH(g) + H2(g) -> C2H6(g) + 2 H2O(g) @ 25.0Â°C

3)
a) Use thermodynamics to prove that the reaction shown below is non-spontaneous at room temperature (25 Â°C).
b) Calculate the temperature at which the reaction would just begin to become spontaneous.

MgCl2(s) + H2O(l) -> MgO(s) + 2 HCl(g)

5) Commercials make the claim that "a diamond is forever." Use thermodynamics to either prove or disprove this claim by calculating:
a) the entropy change.
b) the free energy change for the reaction below, and
c) by comparing DeltaGfÂ° for graphite and diamond.

C(diamond) -> C(graphite)