This chapter begins the saga of one reagent left when all the atoms are ~ 10 10 J s mol-1 5.3.1 Exercise Calculate the energy, in J mol' 1 . Write a thermochemical equation that expresses this. C 2 V 2 0 -> Fe 3 0 4 (s) + Ba(0H) 2 .8H 2 0 (1) and AH f ° = -74kJ mol 1 N.B. In tables of values of heats of combustion.