The standard redox potential values for two half‐reactions are given below. The value for Faraday’s constant is 96.48 kJ V⁻¹ mol⁻¹ and gas constant R is 8.31 J K⁻¹ mol⁻¹.
The standard redox potential values for two half‐reactions are given below. The value for Faraday’s constant is 96.48 kJ V⁻¹ mol⁻¹ and gas constant R is 8.31 J K⁻¹ mol⁻¹.
NAD⁺ + H⁺ + 2 e⁻ ⇌ NADH –0.315 V
FAD + 2 H⁺ + 2 e⁻ ⇌ FADH₂ –0.219 V
Q52 The ΔG°′ for the oxidation of NADH by FAD is
A –9.25 kJ mol⁻¹
B –103.04 kJ mol⁻¹
C +51.52 kJ mol⁻¹
D –18.5 kJ mol⁻¹
Q53 The value of ΔG′, given Keq as 1.7 at 25 °C, will be
A –17.19 kJ mol⁻¹
B –19.8 kJ mol⁻¹
C +52.82 kJ mol⁻¹
D –117.07 kJ mol⁻¹
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Q52 The ΔG°′ for the oxidation of NADH by FAD is –18.5 kJ mol⁻¹ (D)
Calculation: ΔE°′ = E°′(FAD/FADH₂) – E°′(NAD⁺/NADH) = (–0.219) – (–0.315) = +0.096 V
ΔG°′ = –n F ΔE°′ = –2 × 96.48 kJ V⁻¹ mol⁻¹ × 0.096 V ≈ –18.5 kJ mol⁻¹
Q53 The value of ΔG′, given Keq = 1.7 at 25 °C, will be –17.19 kJ mol⁻¹ (A)
Use ΔG′ = ΔG°′ + RT ln Keq
ΔG′ ≈ –18.53 kJ + (8.314 J K⁻¹ mol⁻¹ × 298 K ÷ 1000) × ln 1.7 ≈ –18.53 + 1.31 ≈ –17.19 kJ mol⁻¹
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