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Chemistry Reactions

Find the standard electrode potential, E°, and DG° for the following reaction:

4HIO3(aq) → I2(s) + 2H2O + 5O2(g)

Is the reaction spontaneous? Can iodic acid exist?

Hint: HIO3 is ionized in water.

Solution Preview

4HIO3(aq) → 2 I2(s) + 2H2O + 5O2(g)

First, we look up the half-reactions:

IO3- + 6H+ + 5e- → 1/2 I2 + 3H2O E° = 1.195 V

O2 + 4H+ + 4e- → 2 H2O E° = 1.229 V

Now, we must reverse the second equation and change the sign of E°.

2 H2O → O2 + 4H+ + 4e- E° = -1.229 V

Next, we must make sure that the electrons balance. To do this, we must multiple the first equation by 4 and the second equation by 5. In total, there will be a redox reaction involving 20 electrons.

4 IO3- + 24 H+ + 20e- → 2 I2 + 12 H2O E° = 1.195 V
10 H2O → 5 O2 + 20H+ + ...

Solution Summary

Find the standard electrode potential, E°, and DG° for the following reaction.

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