Question

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

Answer 1

Step-by-step explanation:

Using Gibbs Helmholtz equation:

`\Delta G^o=\Delta H^o-T\Delta S^o`

• ΔG° = negative (spontaneous)
• ΔG° = positive (non spontaneous)

a)
`N_2(g)+3F_2(g)\rightarrow 2NF_3(g)`

ΔH°=-249 kJ = -249000 J , ΔS°=-278J/K

`\Delta G=\Delta H-T(-ve)`

`\Delta G=(-ve)+(ve)`

`\Delta G=(-ve)` (at low Temperature)

`\Delta G=(+ve)` (at high Temperature)

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

b)
`N_2(g)+3Cl_2(g)\rightarrow 2NCl_3(g)`

ΔH°=460kJ = 460,000 J, ΔS°=-275 J/K

`\Delta G=\Delta H-T(-ve)`

`\Delta G=(+ve)+(+ve)`

`\Delta G=(+ve)`

Non spontaneous at all temperatures.

(c)
`N_2F_4(g)\rightarrow 2NF_2(g)`

ΔH°= 85kJ 85,000 J , ΔS°= 198J/K

`\Delta G=\Delta H-T(+ve)`

`\Delta G=(+ve)-(+ve)`

`\Delta G=(+ve)` (at low temperature)

`\Delta G=(-ve)` (at high temperature)

Spontaneous at high Temperature non-spontaneous at low temperature.