You wish to know the enthalpy change for the formation of liquid PCl from the elements. P4(8)+6Cl2(g)4PCl3()8H=? The enthalpy change for the formation of PCl5 from the elements can be determined experimentally, as can the enthalpy, more chlorine to give PCl5(s): P4(s)+10Cl2(g)4PCl5(s)4H=1774.0kJ/molrxnPCl3()+Cl2(g)+PCl5(s),H=123.8kJ/molrxn Use these data to calculate the enthalpy change for the formation of 3.50mol of PCl() from phosphorus and chlorine. Enthalpy change = kJ A item aftemple remationg