Consider these intermediate chemical equations. NO times g plus cap o sub 3 times g rightarrow NO sub 2 times g plus cap o sub 2 times g triangle cap h sub 1 is equal to negative 198 point 9 kJ 3 halves cap o sub 2 g rightarrow cap o sub 3 times g triangle cap h sub 2 is equal to 142 point 3 kJ cap o times g rightarrow 1 half cap o sub 2 g triangle cap h sub 3 is equal to negative 247 point 5 kJ What is the enthalpy of the overall chemical equation NO times g plus cap o times g rightarrow NO sub 2 times g ?