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Absolute Entropy

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Delta G sub f for Al203 = -1582 kJ/mol

delta H sub f for Al203 = -1676 kJ/mol

1. Calculate absolue entropy for S for oxygen (g) if:

S for Al(s) = 164 J/mol K

S for Al2O3 (s) = 51.0 J/mol K

2. Calculate the heat required to raise the temperature of 35.0 g of aluminum from 800 degrees C to 2600 degrees C

3. To calculate the standard heat of formation of C2H5OH Steps are
a) First write the reaction for the heat of formation of C2H5OH
b) Calculate delta S for the reaction
c) Calculate delta G for the reaction
d) Use the equation relating delta G, delta H and delta S to calculate delta H sub f of C2H5OH

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The solution answers each question with explanation. The last question is answered with a description of the step-by-step process. The attachment containing the answers is approximately 400 words long.

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Absolute entropy, free energy and spontaneity

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 DeltaH° and DeltaS° for the following reaction at 25°C.
b) Use the values from a to calculate DeltaG° for the following reaction at 25°C.
c) Explain fully whether this reaction spontaneous or non-spontaneous at 25°C?

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

3)
a) Use thermodynamics to prove that the reaction shown below is non-spontaneous at room temperature (25 °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 DeltaGf° for graphite and diamond.

C(diamond) -> C(graphite)

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