Practice question

Given: For the reaction H₂(g) + Cl₂(g) -> 2HCl(g), if Δ H = -184.6 kJ/mol at 298 K, what is Δ U (R = 8.314 J/mol · K)? These values define the system as per NCERT data. Formula: Δ n_g = 2 - (1 + 1) = 0, so Δ H = Δ U + Δ n_g RT = Δ U. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Δ U = -184.6 kJ/mol. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.