TEXTBOOK 14.57

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Yiwei Zhou 2I
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Joined: Fri Sep 29, 2017 7:07 am

TEXTBOOK 14.57

Postby Yiwei Zhou 2I » Wed Feb 21, 2018 3:48 pm

Aqueous solutions of (a) Mn2; (b) Al3; (c) Ni2; (d) Au3 with concentrations of 1.0 molL1 are electrolyzed at pH  7. For each solution, determine whether the metal ion or water will be reduced at the cathode.

What is the standard reduction potential of water?
2H2O + 2e- = H2 + 2OH-  -0.83V
But the solution manual shows that the reduction potential of water is -0.42V.

Could someone explain this? Thanks a lot!

Dylan Davisson 2B
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Joined: Thu Jul 27, 2017 3:00 am
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Re: TEXTBOOK 14.57

Postby Dylan Davisson 2B » Wed Feb 21, 2018 4:00 pm

Before the questions in the electrolysis section chapter 14, there is a statement saying to use the potentials listed in the standard potentials chart, except for the reduction and oxidation of water at pH=7. Then they say that the equation with water as a reactant (being reduced) has a potential of E=-0.42 V at pH=7, and the equation with water as a product (being oxidized) has a potential of E=+0.82 V at pH=7. In these questions, just use those potentials for water, and it should work out.


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