Question

Calculate the standard enthalpy of formation of CH₃OH (l) from the following data :

(i) CH₃OH (l) + 3/2 O₂ (g) → CO₂ (g) + 2H₂O(l) Δ_rH° = -726 KJ mol^-1

(ii) C(s) +O₂ (g)→CO₂ (g); Δ_rH° = – 393 kJ mol^–l

(iii) H₂(g) +1/2 O₂(g) →H₂O(l) Δ_rH° – 286 kJ mol^–1 .

Answer 1

Aim : C (s) + 2H₂ (g) + 1/2 O₂ (g)→ CH₃ OH,Δ _fH°(l)

Eqn. (ii) + 2 × Eqn. (iii) – Eqn. (i) gives the required eqn. 

with ΔH= – 393 + 2 (–286) – (– 726) kJ mol^–1 =