\"A diamond is forever\" is one of the most successful advertising slogans of al

Question

"A diamond is forever" is one of the most successful advertising slogans of all time. Bui is it true? For the reaction shown below, calculate the standard free energy change at 298 K and determine whether or not a diamond is "forever." C(diamond) rightarrow C(graphite Data: Delta H_f degree (diamond) = 1.895 kJ/mol; S degree (diamond) = 2.337 J mol^-1 K^-1; S degree (graphite) = 5.740 J mol^_1K^-1 A) Delta G degree = 2.19 kJ; forever B) G degree = -1.90 kJ; not forever C) Delta G degree = 1.90 kJ; forever D) Delta G degree = -2.90 kJ; not forever E) Delta G degree =

Explanation / Answer

since deltaG= deltaH-T*deltaS

for graphite to diamond, deltaH=-1.895 Kj/mole

given deltaH= -1.895 Kj/mole and deltaS= change in entropy = 5.740 - 2.337= 3.403J/mole.K

deltaG= -1.895*1000-298*3.403 = -2909 J/mole= -2.909 Kj/mole since deltaH is -ve it is not for ever. D is correct.

2.

deltaH= -136.3-187.7= 51.4 Kj/mole, deltas= 232.7-109.6= 123.1 J/k.mol

deltaG= -105.6+120.4= 14.8 Kj/mole

since deltaG= deltaH-T*deltas

at equilibrium, deltaG=0 and T= Normal boiling point of =deltaH/deltas= 51.4*1000/123.1= 418 deg.c ( E is correct)

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