#methanol decomposition

For CH₃OH(l) → CO(g) + 2H₂(g) , Δ H = 128.10 kJ/mol at 298 K, what is Δ U ? ( R = 8.314 J/mol·K )

For Δ ng = 3 - 0 = 3 , RT = 8.314 × 298 × 10⁻³ = 2.4776 kJ . Using Δ H = Δ U + Δ ng RT , Δ U = 128.10 - 3 × 2.4776 = 128.10 - 7.4328 = 120.67 ≈ 120.7 kJ/mol .

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: Thermodynamic Terms - System Surroundings and Types of Systems