Calculate Delta H and Delta S (3 of 3)

Question

Calculate delta H and delta S for the following reaction and predict whether the reaction is either: always product favored, product favored at only at low temperatures, product favored only at high temperatures, or never product favored.

N2 (g) 2 O2 (g) ====> 2 NO2 (g)

Answer 1

N2 (g)  

dHf = 0 ,

S = 191.5 J

2 O2 (g)

dHf = 0 ,

S = 205.0/mol = 410 J total

2 NO2 (g)

dHf = +33.84kJ/ mol = 67.68kJ total

S = 240.45J/mol = 480.9J total

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dH = prod - reactants

dH =67.68kJ -  ( 0  &  0 )

your answer is dH reaction = +67.68 kJ

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dS = prod - reactants

dS = (480.9J) - (191.5 &  410)

your answer is : dS reaction = -120.6 Joules

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to be spontaneous, we need a dG = -

dG = dH - TdS

with a +

"+" dH & a "-" S  it is a "never product favored."