Question

Consider the reaction: N2(g) + 3 F2(g) → 2 NF3(g) ΔH° = -249 kJ and ΔS° = -278 J/K at 25°C Calculate ΔG° and state whether the equilibrium composition should favor reactants or products at standard conditions.

Answer 1

Answer : The value of
`\Delta G^o` is -166156 J and equilibrium composition should favor products at standard conditions.

Explanation :

Now we have to calculate the Gibbs free energy.

As we know that,

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

where,

`\Delta G^o` = standard Gibbs free energy = ?

`\Delta H^o` = standard enthalpy = -249 kJ = -249000 J

`\Delta S^o` = standard entropy = -278 J/K

T = temperature of reaction =
`25^oC=273+25=298K`

Now put all the given values in the above formula, we get:

`\Delta G^o=(-249000J)-(298K* -278J/K)`

`\Delta G^o=-166156J`

• A reaction to be spontaneous when
  `\Delta G<0` and reaction will be favored in the forward direction that means favored in products.

• A reaction to be non-spontaneous when
  `\Delta G>0` and reaction will be favored in the backward direction that means favored in reactants.

As the value of
`\Delta G` is less than zero that means the reaction is spontaneous and reaction will be favored in the forward direction that means favored in products.

Hence, the value of
`\Delta G^o` is -166156 J and equilibrium composition should favor products at standard conditions.