Question

The reaction of cyanamide, NH₂ CN (s) with dioxygen was carried out in a bomb calorimeter and ΔU was found to be -742.7 kJ mol^-1 at 298 K. Calculate enthalpy change for the reaction at 298 K

NH₂ CN(g) + 3/2O₂ (g) → N₂ (g) + CO₂ (g) + H₂O (l)

Answer 1

ΔU = 742.7 kJ mol^-1

ΔH = ?

ΔH = ΔU + (Δ^ng)RT

Δ^ng = (1 + 1) - 3/2

= +1/2 mol

ΔH = -742.7 + (-1/2) x 8.314 x 10^-3 x 298 J mol^-1

= -742.7 - 1.239

= -741.5 kJ mol^-1