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NEET2012ChemistryElectrochemistryActual

The Gibbs' energy for the decomposition of Al ₂ O ₃ at 500^ C is as follows gathered 2 3 Al ₂ O ₃ 4 3 Al + O ₂ ; _r G=+960 ~kJ ~mol ⁻¹ gathered The potential difference needed for the electrolytic reduction of aluminium oxide ( Al ₂ O ₃ ) at 500^ C is at least

Options

  1. A4.5 ~V
  2. B3.0 ~V
  3. C2.5 ~V
  4. D5.0 ~V

Correct answer

C. 2.5 ~V

Step-by-step solution

The half cell reaction are at anode .2 O ²⁻+4 e⁻ O ₂ ] 3 at cathode . Al ³⁺ Al +3 e⁻ ] 4 Net reaction 4 Al +6 O ²⁻ 3 O ₂+4 Al aligned & or 4 3 Al +2 O ²⁻ O ₂+ 4 3 Al & n= 12 3 =4 & G^ =-n F E^ & Here, G^ =+960 ~kJ ~mol ⁻¹ & =960 1000 ~J ~mol ⁻¹ & n=4 & F=96500 coulomb & 960 1000=-4 96500 E^ & E^ =- 960000 4 96500 & =-2.48 ~V & Potential difference 2.5 ~V aligned

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