6L.7

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Chris Tai 1B
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Joined: Sat Aug 24, 2019 12:16 am

6L.7

Postby Chris Tai 1B » Mon Mar 02, 2020 1:43 pm

Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions:
(a) AgBr(s) -> Ag+(aq) + Br-(aq), a solubility equilibrium
(b) H+(aq) + OH-(aq) -> H2O(l), the Brønsted neutralization reaction
(c) Cd(s) + 2 Ni(OH)3(s) -> Cd(OH)2(s) + 2 Ni(OH)2(s), the reaction in the nickel–cadmium cell

Does that fact that these are solubility/Bronsted reactions affect how you set up the cell diagram?
Could you help walk me through part a of this question? How do you determine which compounds/elements are part of the anode side of the reaction, and vice versa for the cathode?

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Re: 6L.7

Postby Chem_Mod » Mon Mar 02, 2020 4:34 pm

Use appendix 2B and look for half reactions that use the compounds listed in the problem and can be combined to eliminate any species not listed (not including water, H+, OH-). The reaction with the most positive reduction potential will occur at the cathode and the other reaction at the anode

For part a:
Reactions with AgBr: AgBr + e- --> Ag + Br- E: +0.07

Need to eliminate Ag
Use: Ag+ + e- --> Ag E: +0.80

The first reaction has the less positive E, therefore it will be the oxidation reaction:
Ag + Br- --> AgBr + e- E: -0.07
Ag+ + e- --> Ag E: +0.80
----------------------------------------
Ag+ + Br- --> AgBr. E: +0.73


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