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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)

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Answer:

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

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