Use the tabulated values of ΔG∘f to calculate E∘cell for the fuel cell breathalyzer, which employs the reaction below. (ΔG∘f for HC2H3O2 (g) = - 374.2 kJ/mol.) CH3CH2OH (g) + O2 (g) →HC2H3O2 (g) + H2O (g)

0.97 V

Explanation:

The equation relating ΔGºf to Eºcell is

ΔGºf = - nFEºcell, where

ΔGºf = Gibbs Free energy change of formation at STP in Joules

n = number of moles of electron

F = Faraday constant, 96,500 coluomb

Eºcell = emf of the cell at standard conditions

The redox reaction is

CH3CH2OH (g) + 2H2O ⇒ HC2H3O2 (g + 4 H⁺ + 4e⁻

O2 + 4 H⁺ + 4e⁻ ⇒ 2 H2O

Eºcell = - ΔGºf / nF = - 374.2 x 1000 J / (4x 96500 colulomb) = 0.97V