The oxidising power of iodine in aqueous solution can be judged from the energy of the change 2 1 I 2 ( g ) → I − ( aq ) . Using Δ H d i ss ∘ ( I 2 ) = 151 kJ/mol , Δ H e g ∘ ( I ) = − 295 k

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The oxidising power of iodine in aqueous solution can be judged from the energy of the change 2 1 ​ I 2 ​ ( g ) → I − ( aq ) . Using Δ H d i ss ∘ ​ ( I 2 ​ ) = 151 kJ/mol , Δ H e g ∘ ​ ( I ) = − 295 kJ/mol and Δ H h y d r a t i o n ∘ ​ ( I − ) = − 293 kJ/mol , the energy involved is:

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Only half a mole of I 2 ​ is dissociated: 151/2 = + 75.5 kJ . Total = 75.5 − 295 − 293 = − 512.5 kJ/mol . ( − 437 comes from forgetting the factor 2 1 ​ .) Answer: (A).

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