If a substance undergoes electrolysis and a brown solid forms on one electrode and a gas on the other, from this we can conclude the original substance must have been: a. An element b. A compound c. A mixture

b. a compound.

Explanation:

Electrolysis is described as a mechanism in which ionic compounds are decomposed into their elements by transmitting a direct electric current via the compound in a liquid state. At the cathode, the cations are reduced and anions at the anode are oxidized. There is an exchange between ions and atoms in the electrolysis process caused by the addition or removal between electrons from the external circuit. As per the question, the original substance is a compound because the electrolysis method is used to obtain pure elements from their respective compound.