Comparison of ∆G of the dissociation reaction and ∆Gf of ammonium carbamate?

Question

Comment briefly on the relative values of ∆G standard of the dissociation reaction and the ∆Gf standard of ammonium carbamate in relation to the ‘thermal stability’ of the substance.

∆G standard = 20.01293819 kJ mol-1

∆Gf standard = 446.0129382 kJ mol-1

What do these values mean please?

Sorry, ∆Gf = -446.0129382 kJ mol-1 is negative, not positive.

Answer 1

Hello!

I was struggling with my lab report too on the dissolution reaction of Borax a few weeks ago. The entire thing about gibbs' free energy is so confusing!

Under favourable conditions, ∆G˚ is negative, i.e. the dissolution reaction of ammonium carbamate is spontaneous. This means that the solubility of ammonium carbamate in water is high. However, if conditions are unfavourable, ∆G˚ will be positive, i.e. the dissolution reaction of ammonium carbamate will be non-spontaneous. This means that the solubility of ammonium carbamate in water will be low. Since you have a positive ∆G˚ value, it can be concluded that ammonium carbamate is not very soluble in water (under standard conditions).

∆G˚ can also be affected by temperature. According to the equation ∆G˚ = -RT ln (K), the value of ∆G˚ becomes more negative when temperature increases. Since a more negative value for ∆G˚ signifies a more spontaneous reaction, the solubility of ammonium carbamate in water would increase with temperature.

Hope this would be of help to you.

There's always something wrong when I post this under the source column, so I'll post the source here:

George M. Bodner, Gibbs’ Free Energy, Purdue University, Indiana, United States, 2000. Available from http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch21/gibbs.php#temp

Answer 2

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Answer 3

DeltaG0 for the reaction, ie.e. formation of product from reactants

DeltaGf0 for formation of the product from the elements(in their standard form)