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K s p of A l ( O H ) 3 = 1 0 - 36 and E Al 3+ /Al o = − 1 .66 V Reduction potential of Al 3+ /Al couple at pH = 12 and 298 K is

Options

  1. A1 .07 V
  2. B2 .25 V
  3. C− 1 .07 V
  4. D− 2 .25 V

Correct answer

D. − 2 .25 V

Step-by-step solution

A l 3 + + 3 e - → A l E = E o - 0.059 3 log ⁡ 1 A l 3 + at pH = 12 ⇒ pOH = 14 − 12 = 2 ⇒ OH − = 0 .01 M A l + 3 = 1 0 - 36 [ O H - ] 3 = 1 0 - 36 ( 0.01 ) 3 = 1 0 - 30 ∴ E = - 1.66 - 0.059 3 log ⁡ 1 1 0 - 30 = − 1 .66 − 0 .059 3 × 30 = − 1 .66 − 0 .59 = − 2 .25 V

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