We are given the following balanced chemical equations:
P4(s) + 6Cl2(g) → 4PCl3(g), ∆H = –1224 kJ
4PCl3(g) + 4Cl2(g) → 4PCl5(g), ∆H = –372 kJ
adding the two equations, we arrive at a final equation:
P4(s) + 10Cl2(g) → 4PCl5(g)
Now, we need to find the total enthalpy of this reaction. Add both enthalpies of the two initial equations:
∆H = –372 kJ + -1224 kJ
∆H = –1596 kJ
Therefore, the total enthalpy change of burning phosphorus with chlorine is -1596 kJ, meaning the reaction is exothermic and produces heat.
