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NEET CHEMISTRYElectrochemistryMedium

Question

Consider the following reaction: 43Al(s)+O2(g)23Al2O3(s) ; ΔG=827 kJ mol1\frac{4}{3}Al(s) + O_2(g) \rightarrow \frac{2}{3}Al_2O_3(s) \ ; \ \Delta G = -827 \text{ kJ mol}^{-1} The minimum e.m.f. required to carry out the electrolysis of Al2O3Al_2O_3 is: (Given F=96500 C mol1F = 96500 \text{ C mol}^{-1})

A

2.14 V

B

4.28 V

C

6.42 V

D

8.56 V

Step-by-Step Solution

For the electrolysis of Al2O3Al_2O_3, the reaction is the reverse of the given formation reaction: 23Al2O3(s)43Al(s)+O2(g)\frac{2}{3}Al_2O_3(s) \rightarrow \frac{4}{3}Al(s) + O_2(g) Therefore, the Gibbs free energy change for the electrolysis is ΔG=+827 kJ mol1=827000 J mol1\Delta G = +827 \text{ kJ mol}^{-1} = 827000 \text{ J mol}^{-1}.

The number of electrons involved (nn) in this reaction can be calculated from either the reduction of Al or oxidation of O: Number of moles of Al formed = 43\frac{4}{3} moles. Since Al3++3eAlAl^{3+} + 3e^- \rightarrow Al, the total moles of electrons (nn) = 43×3=4\frac{4}{3} \times 3 = 4 moles of electrons.

Using the relation between Gibbs free energy and cell potential: ΔG=nFE\Delta G = nFE 827000=4×96500×E827000 = 4 \times 96500 \times E 827000=386000×E827000 = 386000 \times E E=827000386000=2.142 V2.14 VE = \frac{827000}{386000} = 2.142 \text{ V} \approx 2.14 \text{ V}

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Electrochemistry. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYElectrochemistryconsiderfollowingreactionfracalsrightarrow

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