Question

How is the electrolysis of `MgCl_2` performed?

Answer 1

to make electrolysis of a solution of MgCl2 you must put into a tank two electrodes with a potential difference of some Volts in continuous current. Cations ( H+ and Mg 2+) go to the cathode,( in this case negative); while anions (OH - and Cl-) go to the anode (positive). Become free the ions that require less energy (less potential difference) i. e. H+ to the cathode is transformed in H2 gas, while to the anode, while to the anode you can find Cl2. Really OH- should require less energy ( E = 1,23 -0,06 pH Volt but it has a very high overvoltage of electrode) than Cl2 (E= 1,35 Volt) so you pratically have an anomaly than the theory