Question

Calculate standard Gibbs energy change for the reaction 4NH3+5O2-4NO+6H2O

Answer 1

• Standard Gibbs energy for the given reaction is -1009.2 kJ.
• Since standard Gibbs energy is negative so the process is feasible.

Given-

Standard free energies of formation (Δf G°) for NH₃ (g) = – 16.8 kJ/ mol

Standard free energies of formation (Δf G°) for NO (g) = + 86.7 kJ / mol

Standard free energies of formation (Δf G°) for H₂O (l) = - 237.2 kJ / mol

By using the formula

∴ Δf G° = ∑f G° (Products) - ∑ Δf G° (Reactants)

where  ∑ represents the sum.

So by putting the values, we get -

= [4 × Δf G° (NO) + 6 × Δf G°(H₂O)] – [4 × Δf G° (NH₃ ) + 5 × Δf G° (O₂ )]

= [4 × (86.7) + 6 × (–237.2)] – [4 × (– 16.8) + 5 × 0] = – 1009.2 kJ

Hence Standard Gibbs energy for the given reaction is -1009.2 kJ.

Regards