Glucose is the major fuel for most living cells. The...

Glucose is the major fuel for most living cells. The oxidative breakdown of glucose by our body to produce energy is called respiration. The reaction for the complete combustion of glucose is $$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s)+6 \mathrm{O}_{2}(g) \longrightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l)$$ If this combustion reaction could be harnessed as a fuel cell, calculate the theoretical voltage that could be produced at standard conditions.

Glucose is the major fuel for most living cells. The oxidative breakdown of glucose by our body to produce energy is called respiration. The reaction for the complete combustion of glucose is
$$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s)+6 \mathrm{O}_{2}(g) \longrightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l)$$
If this combustion reaction could be harnessed as a fuel cell, calculate the theoretical voltage that could be produced at standard conditions.

Key Concepts

Fuel Cell

A fuel cell is an electrochemical device that converts the chemical energy of a fuel directly into electrical energy through redox reactions. It operates by oxidizing a fuel at the anode and reducing an oxidant at the cathode, with electrons flowing through an external circuit to produce power. Fuel cells are distinguished by their high efficiency and low emissions compared to combustion-based energy conversion methods.

Redox Reaction

Redox (reduction-oxidation) reactions involve the transfer of electrons between chemical species. In these reactions, one compound is oxidized while another is reduced. Understanding redox reactions is crucial in many energy conversion processes, including the operational principles of fuel cells, where the electron transfer underlies the generation of electrical energy.

Standard Conditions

Standard conditions refer to a set of defined parameters (typically 1 atm pressure, 298 K temperature, and 1 M concentrations for solutions) under which thermodynamic properties such as free energy and electrode potentials are measured. Using standard conditions allows for consistent comparison of reaction energetics and is essential when calculating theoretical voltages in electrochemical systems.

Gibbs Free Energy and Electrode Potential

The relationship between free energy change and electrode potential is given by the equation ?G° = -nFE°, where ?G° is the standard Gibbs free energy change, n is the number of moles of electrons transferred, F is Faraday’s constant, and E° is the standard electrode potential. This equation provides a means to calculate the theoretical voltage of an electrochemical cell from thermodynamic data, linking chemical energetics to electrical work.

Faraday's Constant

Faraday's constant (approximately 96485 coulombs per mole) represents the charge of one mole of electrons. It is a fundamental constant in electrochemistry used to relate the amount of substance undergoing oxidation or reduction to the electrical charge transferred in redox reactions, and is essential in calculating cell potentials from free energy changes.

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