What is the value of ΔH˚ (in kJ) for the reaction N2O + NO2 → 3 NO at 25 °C?
(A) 156.2
(B) 5.5
(C) 53.2
(D) 109.0
....................S...........ΔGf
................J/mol K.....kJ/mol
NO(g)..........211 ..........86.7
NO2 (g).......240 ..........51.8
N2O(g)........220 .........103.6
The answer is A, but why? Ive tried to convert the values to ∆H˚ but no luck.
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Verified answer
we know that
delta G = delta H - T*S
or
delta H = delta G + T*S
so
delta H for NO = 86.7 + .211*298 = 149.6
delta H for NO2= 51.8 + .240*298 = 123.3
delta H for N2O= 103.6 + .220*298 = 169.2
delta H for reaction = 3*delta H for NO - delta H for NO2 - delta H for N20 = 149.6*3 - 123.3 - 169.2 = 156.3 kJ
i hope this helps..
neways thanks