Fluorine Flame Calorimetry III. The Heat of Formation of Chlorine Trifluoride at 298.15 K

The standard heat of formation of chlorine trifluoride (gas) at 298.15 K has been determined to be - 164.65 kj mol-1 (-39.35 kcal mol-1) with an overall experimental uncertainty of 5.14 kj mol-1 (1.23 kcal mol-1). This value is derived from the enthalpies of the following reactions which were measured directly in a flame calorimeter operated at 1 atm pressure and 303.5 K, together with data from previous investigations.ClF 3 ( g ) + 2 H 2 ( g ) + 100 H 2 O ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) ( 1 / 2 ) Cl 2 ( g ) + 1 / 2 H 2 ( g ) + [ 3 HF ⋅ 100 H 2 O ] ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) The enthalpy of formation of [HC1‧100H2O](l) was also measured. The average Cl - F bond energy in chlorine trifluoride is calculated to be 160.1 kj mol-1 (38.26 kcal mol-1).