|MadSci Network: Chemistry|
Nathan and Matthew: The electrolysis that you did was that of salt water, not simply water. The addition of the salt created a different system. The reaction for your electrolysis is: H2O + NaCl ---> H2 + Cl2 + NaOH You had hydrogen gas as the cathode, but chlorine gas (luckily not much) at the anode with sodium hydroxide solution in the apparatus. Most likely the chlorine reacted with the copper wire to form CuCl2 or Cu2Cl2 which then reacted with the NaOH to form Cu(OH)2 which was most likely your precipitate. Fortunately you didn't try to breath the gas at the anode as it wasn't oxygen but chlorine which can be deadly causing severe erosion of mucous membranes and pulmonary edema leading to death. Improvising with different equipment variations can significantly effect the outcome of a reaction. Be very careful with any future experiments.
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