Question

The reaction of cyanamide, NH₂CN (s) with oxygen was carried out in a bomb calorimeter and AU was found to be – 742.7 kJ mol1 at 298 K. Calculate the enthalpy change for the reaction at 298 K.

Answer 1

NH₂CN(S) + 3/2O₂ (g) → N₂ (g) + CO₂ (g) + H₂O(l) 

∆U = 742.7 kJ mol ; 

∆n(g) =2 – 3/2= + 0.5 

R = 8.314 × 10 kJ K mol ; 

T = 298K 

According to the relation, ∆H = ∆U + ∆n RT 

∆H = -742.7 kJ + 0.5 mol × 8.314 × 10 kJ K mol × 298 K 

= - 742.7 kJ + 1.239kJ 

= - 741.5 kJ