What is the fomula of chemical energy?

Answer 1

Assuming chemical energy means the enthalpy change (measured in joules), there are several methods to calculate chemical energy, although there is no one 'formula'. The simplest way is to calculate the bond energies between the atoms in the molecules and subract the total initial energy from the total final energy.

If bond energies aren't provided, more complex methods are required. If you're looking for the change in enthalpy in the reaction A --> D, and are given the changes in enthalpy for A --> B, B --> C, and C --> D, then adding the enthalpy changes for the given reactions will give you the desired enthalpy change.