At a potential of --1.0 V (versus SCE), carbon tetrachloride in methanol is reduced to chloroform at a Hg cathode:
At -1.80 V, the chloroform further reacts to give methane:
Several 0.750-g samples containing CCl4 CHCI3 and inert organic species were dissolved in methanol and electrolyzed at -1.0 V until the current approached zero. A coulometer indicated the charge required to complete the reaction, as given in the second column of the following table. The potential of the cathode was then adjusted to -1.80 V. The additional charge required to complete the reaction at this potential is given in the third column of the table. Calculate the percent CCl4 and CHCl3 in each mixture.
