Classify each of the following reactions as one of the four possible types:

1. spontaneous at all temperatures;
2. nonspontaneous at all temperatures;
3. spontaneous at low t; nonspontaneous at high t;
4. spontaneous at high t; nonspontaneous at low t.

(a) n2(g)+3f2(g)→2nf3(g); δh∘=−249kj; δs∘=−278j/k
(b) n2(g)+3cl2(g)→2ncl3(g); δh∘=460kj; δs∘=−275j/k
(c) n2f4(g)→2nf2(g); δh∘=85kj; δs∘=198j/k

Explanation:

Using Gibbs Helmholtz equation:

a)

ΔH°=-249 kJ = -249000 J , ΔS°=-278J/K

(at low Temperature)

(at high Temperature)

Spontaneous at low Temperature , Non-spontaneous at high Temperature;

b)

ΔH°=460kJ = 460,000 J, ΔS°=-275 J/K

Non spontaneous at all temperatures.

(c)

ΔH°= 85kJ 85,000 J , ΔS°= 198J/K

(at low temperature)

(at high temperature)

Spontaneous at high Temperature non-spontaneous at low temperature.

the answer to this question is 3.