ElectrochemistryhardNUMERICAL

By strictly applying Faraday's laws to the electrolysis of aqueous using completely inert electrodesElectrochemistry Chemistry Question

Question

By strictly applying Faraday's laws to the electrolysis of aqueous $MgSO_4$ using completely inert electrodes, what is the exact integer ratio of the total moles of gas evolved at the cathode to the total moles of gas evolved at the anode?

Answer: 2

💡 Solution & Explanation

In aqueous $MgSO_4$, water is reduced at the cathode and oxidized at the anode. Cathode reaction: $2H_2O + 2e^- \rightarrow H_2 + 2OH^-$ (n-factor for $H_2 = 2$). Anode reaction: $2H_2O \rightarrow O_2 + 4H^+ + 4e^-$ (n-factor for $O_2 = 4$). Faraday's law dictates equivalents are equal: Equiv($H_2$) = Equiv($O_2$). Therefore, Moles($H_2$) $\times 2$ = Moles($O_2$) $\times 4$. The ratio Moles($H_2$) / Moles($O_2$) = $4 / 2 = 2$.

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