Phosphoryl chloride (POCl₃) can be formed from the reaction of phosphorus trichloride (PCl₃) and oxygen gas (O₂). The unbalanced reaction is shown below:
PCl₃(g) + O₂(g) → POCl₃(g)
In POCl₃, the O atom and the three Cl atoms are bonded to the central P atom. Referring to the given in the table below, calculate the approximate enthalpy of the reaction and determine whether the reaction is endothermic or exothermic.

• A. –2.5×10² kJ; exothermic
• B. +1.0×10² kJ; endothermic
• C. –1.0×10² kJ; exothermic
• D. +3.4×10² kJ; endothermic
• E. –3.4×10² kJ; exothermic

Answer: (C)