Electrolysis Lab

In our most recent lab, we went continued our exploration of voltaic cells and electrolysis. Specifically, we observed an electrolysis reaction. At the cathode, reduction was occuring, with a half reaction of H2O (l) + 2e- => 2H2 (g) + 2OH-. At the anode, oxidation was occuring, with a half reaction of 2H2O (l) => O2 (g) + 4H+ + 4e-. We knew that these reactions occured because oxygen and hydrogen gases were collected in the tubes.


Structurally, a voltaic cell differs from an electrolytic cell because the reaction occurring in a voltaic cell is spontaneous (does not need an external energy source). This means that the electrodes must be placed in solutions of their own ions, because one material will precipitate out of solution, and one will lose electrons, forming more ions. In order to balance the charges in the reaction, a salt bridge must be used. If the solutions were not neutral, the reaction could not occur.

A non-spontaneous redox reaction is a reaction in which outside energy is required. The reaction at hand does not occur spontaneously because the reduction potential is negative, meaning a reduction oxidation reaction cannot occur unless another source of energy is available. For our reaction, a battery was used as an external energy source.

(Still confused on faraday)


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