Consider the following reaction at constant P. Use the information here to deter

Question

Consider the following reaction at constant P. Use the information here to determine the value of ?Ssurr at 355 K. Predict whether or not this reaction will be spontaneous at this temperature.

2 NO(g) + O2(g) ? 2 NO2(g) ?H = -114 kJ

Consider the following reaction at constant P. Use the information here to determine the value of ?Ssurr at 355 K. Predict whether or not this reaction will be spontaneous at this temperature.

2 NO(g) + O2(g) ? 2 NO2(g) ?H = -114 kJ

?Ssurr = +114 kJ/K, reaction is spontaneous ?Ssurr = +321 J/K, reaction is spontaneous ?Ssurr = -321 J/K, reaction is spontaneous ?Ssurr = +114 kJ/K, reaction is not spontaneous ?Ssurr = +321 J/K, it is not possible to predict the spontaneity of this reaction without more information.

Explanation / Answer

we know that

dSsurr = -dHsys / T

given

dHsys = -114 kJ

Temperature T = 355 K

so

dSsurr = - ( -114x 1000) / 355

dSsurr = 321.12 J/K

so

the value of dSsurr is +321.12 J/K

b)

for a reaction to be spontaneous

dG<0

also

dStotal = dSsys + dSsurr >0

we know that

dG = dHsys - TdSsys

now assume

dG<0

(-114 x 1000 ) - (355 x dSsys) <0

355 x dSsys > -114 x 1000

ds sys > -321

dS sys > - dSsurr

dS sys + dSsurr > 0

dS total > 0

so our assumption is correct

so the given reaction is spontaneous

so the final answer is

?Ssurr = +321 J/K, reaction is spontaneous

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