Final answer:
In cellular reactions, ΔH is approximately equal to ΔE because they typically occur at constant pressure with negligible volume change. The cell potential (Ecell) reflects the spontaneity of a reaction, with a positive Ecell indicating a spontaneous reaction. The standard cell potential (E°cell) relates to reaction spontaneity and is linked to ΔG° and the equilibrium constant (K).
Step-by-step explanation:
In cellular reactions, which occur in the liquid phase, the relationship between enthalpy (H) and internal energy (E) is important to understand. The change in enthalpy (ΔH) is related to the change in internal energy (ΔE) by the equation ΔH = ΔE + PΔV, where P is the pressure and ΔV is the change in volume. Since cellular reactions typically occur at constant pressure and often involve liquids and solids where the volume change is negligible, the change in enthalpy is approximately equal to the change in internal energy. When discussing electrochemical cells such as the one mentioned, the cell potential (Ecell) indicates the overall voltage of the cell.
Ecell can be described by the equation Ecell = Ecathode - Eanode. A positive Ecell means that the reaction will occur spontaneously as written, whereas a negative Ecell indicates that the reaction will proceed spontaneously in the opposite direction. The standard cell potential (E°cell) measures the cell potential under standard-state conditions and is critical for determining reaction spontaneity, which in turn is related to the standard free-energy change (ΔG°) and the equilibrium constant (K).