# Heat energy vs. electrical energy in a galvanic cell or in an electrochemical reaction

How can someone determine heat energy released during an electrochemical reaction?

Let's assume a simple galvanic cell at standard environment:

$$\ce{Zn(s) -> Zn^2+(aq) || Cu^2+(aq) -> Cu(s)}$$

Electrical energy can be derived from the electrode potential and electron flow, but how the heat release can be calculated? What's the heat release when $\ce{Zn(s)}$ gets solvated to $\ce{ZnSO4(aq)}$, and whats the heat release when $\ce{Cu^2+}$ ions gets plated to the electrode?

I'm using term "heat release", because I get confused about the enthalpy in electrochemical cells, since some of enthalpy seems to be connected to electrical work as well.

• I will write a proper answer if I have the time, but Bard&Faulkner has a great discussion of this phenomenon in the beginning of Chapter 2. If you have access to a library that has it, it is section 2.1.2 – Burak Ulgut Apr 11 '17 at 12:31

Operational electrochemical cells have $$\Delta G\lt0$$
And, $$\Delta G=-nFE$$ $$\Delta G=\Delta H-T\,\Delta S$$
$$\Delta H=-nFE+nFT\frac{\mathrm d\Delta G}{\mathrm dT}\quad\text{at contant }p$$