Which of the following metals can offer cathodic protec-tion to iron? Select all the correct choices. Mn, Ni, Pb, Sn, Al

Video transcript

Welcome back, everyone. We need to determine the identity of the metals that can be used for cathartic protection of iron. We're considering nickel, magnesium, cobalt, zinc or cadmium, recall what cathartic protection really means. And we would realize that it's describing a metal that is connected to a second medal where the second metal is going to be more easily oxidized. So ultimately, being more easily oxidized means that this second metal is going to lose electrons more easily. So we're going to need to consider in our textbooks, our standard reduction potential table where we want to specifically make note of the reduction potentials of our given elements under standard conditions where the greater the value of our reduction potential that would correspond to an atom that is more prone to reduction. And on the contrary, the lower the value of our standard reduction potential that would correspond to an atom that is more prone to oxidation. So with these notes in mind, we need to make note of also the reaction for the formation of solid iron metal in which iron as a two plus catalon will gain two electrons. And as a product we would form our solid iron metal. This reaction has an associated reduction potential equal to a value of -0.45V. So if we want to choose from our given medals, we want to find the metal that has a reduction potential that is even lower than this value because it would then be more prone to oxidation. Meaning that that metal would be oxidized first instead of our iron, which we want to protect from being oxidized so that it doesn't rust. So let's consider our first medal given which is nickel. So for nickel recall that we form the two plus catalon in which we would gain two electrons to form nickel solid. And according to our standard reduction potential table, this reaction has a standard reduction potential equal to a value of -0.26V. Now this reduction potential is less negative than our reduction potential of iron. And so we would say that therefore nickel is more prone to reduction. And so it's not going to be used for cathartic protection. So we'll say not for cathartic protection. So now let's consider now that we've ruled out Nicole, let's consider magnesium next. So for magnesium, we also have a two plus cat down in which we'll gain two electrons to form Solid Magnesium, which according to our standard reduction potential, we have a reduction potential equal to negative 2.37V. So we have an even more negative magnitude for the reduction potential of this metal in comparison to iron. And so we can say that therefore, magnesium is more prone to oxidation. And we can confirm that it would be great as a cathartic protector for iron. So it would be helpful in preventing iron from oxidizing because instead magnesium would oxidize. So now let's consider our next element Cobalt, we can confirm magnesium is a good metal to choose. So considering cobalt, we have the cobalt two plus caddy on which forms we would gain two electrons and form are solid Cobalt metal. And the standard reduction potential. According to our table and our textbooks for this reaction is equal to negative 0.28 volts, which is also just like for the case of nickel, more prone to reduction and therefore not good for cathartic protection. So we would rule out Cobalt from our list of options. Now let's move on to consider zinc. So for zinc, we have a two plus carry on gaining two electrons to form solid zinc. And with this reaction, we have a standard standard reduction potential in our tables equal to a value of negative 0.76 volts. This is a bit more negative in magnitude than our reduction potential for iron above. And so we would say that therefore, zinc is more prone to oxidation and therefore is a good cathartic protector for iron. So we can also consider zinc as one of our answer choices for this example. And then for cadmium, we're going to write out its reaction where we have our cadmium two plus Catalan gaining two electrons to form solid cadmium in which we have a reduction potential in our textbooks of negative 0.40 volts comparing this to our reduction potential of iron being negative 0.45 volts, it's less negative in magnitude. And so it's not going to be a great cathartic protector because cadmium is more prone to reduction. So we would rule out cadmium from our answer choices because it's similar to nickel and cobalt. So we're between magnesium and zinc and between our two options, magnesium and zinc, we see that the more negative reduction potential is negative 2.37 volts for solid magnesium, which is more prone to oxidation. And so for our final answer, we would confirm that the two medals because it looks like we actually don't have to only pick one. We can pick two medals. The identity of the two metals that can be used as cathartic protectors with the most negative magnitude of reduction potentials are magnesium and sink. And our final answer is highlighted in yellow will correspond to choice C in the multiple choice. So this completes this example. I hope everything I reviewed was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.