I know this is probably such a basic question with fundamental explanations and I can't help from overthinking.
So if we have an equilibrium would the addition of heat as in an increase in temperature be added to the reaction side or product side. How does this apply to the addition of other chemicals into the equation? Will everything always be added to the left side since it is the reactants that form the product?
(reactants). (product)
$$\ce{[CuCl4]^2- + 4H2O <=> [Cu(H2O)4]^2+ + 4 Cl-}$$
Energy, usually energy involving the kinetic and quantum mechanical [rotational, vibrational, electronic] energy but that can also be electrical or photonic, is involved in chemical reactions in 2 ways. The first is activation energy, there must be enough energy available for the reaction to have an effective rate. This rate could be fractional seconds or eons. Adding heat energy increases the rate of both forward and reverse reactions and changes the equilibrium position.
The second is the change in chemical potential energy in the breaking and forming of chemical bonds. The reactants with the stronger overall bonds release heat to the system; removing heat [or work] forces the reaction in that direction. If heat is added the reaction is forced in the reverse direction [provided equilibrium can be obtained otherwise an alternative mechanism must be found].
Writing a reaction in the exothermic direction makes heat a product and it can be treated thusly. [or in reverse heat is a reactant]. Whether the reaction is reversible depends on complexity or entropy change the; simpler the more possibility it is reversible.
