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 Incoming links: Standard Gibbs energy of reaction

ln K_{a} = - \frac{Δ _{r} G ^{\circ}}{RT} = - \frac{41133}{8.3145 ( 298 )} = - 16.6011, K_{a} = 6.17 \times 1 0^{- 8} .

The positive standard Gibbs energy of reaction means that dissociation is unfavourable when every thermodynamic activity equals one; it does not forbid partial dissociation. The corresponding

p K_{a} = - lo g_{10} K_{a}

is about

7.21

For the cell reaction normalized as in 4(b)(i), six moles of electrons are transferred per mole of reaction. Therefore

Δ_{r} G = - 6 FE = - 6 (96485) (1.5180208) = - 8.78797 \times 1 0^{5} J mo l^{- 1} \approx - 879 kJ mo l^{- 1} .

This is the Gibbs energy of reaction at the stated composition and gas pressure, not the standard Gibbs energy of reaction. Its negative sign confirms thermodynamic favourability in the written direction under those conditions.