Hi all! Not sure how this will work, but I've got a question about one of the Bio passages: Question ID # 400573

Re: Choice B. If a protective layer of Mg(OH)2 forms on the metal disk, then how will the mass of the disk be an accurate representation of how much Mg is used up in the reaction? Any input is appreciated, thanks!

I haven't done this question yet, but I believe it is related to corrosion of metal alloy in a galvanic cell.
When Mg2+ is not exposed to an aqueous environment, the natural oxide layer protects Mg from undergoing corrosion. But lets say when it is introduced to a solution that has low pH (lets say Cl- solution) Mg2+'s oxide film is broken and the surface is exposed, and leads to corrosion. Then if you increase the pH of the solution, another film is formed (layers of Mg(OH)2 and MgO) This film, although decreases the rate of corrosion. This film is basically the fraction of total corroded Mg2+ that forms the protective layer in galvanic cell. Then mass of the disk will include the Mg2+ that is used in the reaction. Some one pls correct me if I am wrong.....
edited by on 2/29/2020
edited by on 2/29/2020
edited by on 2/29/2020