Consider these intermediate chemical equations. cap p sub 4 times s plus 6 Cl sub 2 g rightarrow 4 PCl sub 3 g triangle cap h sub 1 is equal to negative 2 comma 439 kJ 4 PCl sub 5 g rightarrow cap p sub 4 times s plus 10 Cl sub 2 g triangle cap h sub 2 is equal to 3 comma 438 kJ What is the enthalpy of the overall chemical reaction PCl sub 5 times g rightarrow PCl sub 3 times g plus Cl sub 2 times g ?