Analyte Oxidation State - Video Tutorials & Practice Problems

Analyte Oxidation State

So within a given redox detraction we have the an elite and we have our tight trend. We're going to say here that it is common for the an elite to exist in multiple oxidation states while in solution so will possess multiple charges. And we're gonna say when we do any type of quantitative analysis, it has to be converted to just one oxidative state. Now we're gonna say for example, iron itself can exist as two different forms. It can exist as iron too or iron three. Now if we have a solution that contains both of these ions that won't help us in terms of our redox filtration. So what we would do is we could basically add either a reducing agent or an oxidizing agent to this solution of these two ions and in that way get rid of one of them. Once we've gotten down to one oxidation state for our iron we can utilize that ion and either do an oxidation with it or a reduction. Now a common type of oxidizing agent is tends to be used with these ions. Is your Siri. Um For ion serum for ion is one of the strongest oxidizing agents that exists. So as an oxidizing agent it would basically remove an electron from iron. So if we're going to remove an electron from iron, that means iron is gonna become more positive. And since these are the two forms that it can exist in it have to react with F. E. Two plus removing an electron from it means that iron now becomes F. E. Three plus this year it oxidizes iron too by removing its electron so it accepts that electron. So now it becomes Siri um three plus. And that's how these oxidizing agents and reducing agents behave. The either help to oxidize one of the forms of a particular ion. So at the end our solution possesses only one particular oxidation state for that given ion from there, we then continue with our redox filtration. Now here, if we're talking about reducing agents, we call them auxiliary reducing agents. We're gonna say an auxiliary reducing agent represents an easily oxidized metal. Typically we have zinc and silver but also less commonly used tin and cadmium here there are reducing agents so they're going to help reduce one of the ions forgiven solution. And it's part of what we call the pre reduction step. We're gonna reduce one of these ions so that at the end we have only one of the ions remaining that can then undergo some type of redox filtration. Now we're gonna say that these oxygen reducing agents there present as either solids powders or part of what we call a reduction column. Now they reduced the an elite to one oxidation state. Once the an elite has obtained a single oxidation state, the reducing agent is then removed and then we do our redox filtration. Now we're gonna say that the two types of reduction columns that exists in the first one we have what's called the jones reducto er and here this is just your reduction column is filled with a zinc amalgam. So that's basically zinc bonded to mercury. And we're gonna say in the process the zinc metal reduces the an elite while it is oxidized. So here are zinc amalgam, it's going to help to reduce the an elite in the process. We have our zinc here, that's two plus. And remember if it's helping to reduce the other species, that means it itself is being oxidized. So that's how it loses these two electrons. And then here we have our mercury liquid that has basically decoupled itself from the zinc amalgam. Now our other common reduction column is called the Walden reducto. Er So here this one is filled with basic little pebbles or Granules of solid silver metal. And we're gonna say while the analyzed solution is infused with acid. So the solution itself is acidified. Here we have our silver solid, it's going to react with the chloride ion, it gets oxidized and becomes plus one and that's how it's able to combine with the chloride ion that's minus one here. This represents the electron that it's lost, that electron that it's lost. Will then go to the an elite and reduce it so that we have only one oxidation state for that particular an Elite. Remember the whole point of an auxiliary reducing agent is to donate an electron or more to an an elite in order to have only one oxidation state at the end. Once we get to that one ion, we can do a redox filtration with that, given an elite, now that we've talked about auxiliary reducing agents, come back and see what we say in terms of auxiliary oxidizing agents.

Analyte Oxidation State

Alright guys, so now we're gonna take a look at our auxiliary oxidizing agents, we're gonna say the ox. Ilary oxidizing agents, basically just oxidize the an elite. And in the process of this they themselves are reduced because they're oxidizing the an elite to just one oxidative state. We say that this is part of our pre oxidation stage. So we're gonna create or keep the an elite that has the more positive charge which therefore corresponds to the greater oxidation number. Now we're gonna say here that peroxide dye sulfate which is this represents a powerful oxidizing agent that works in conjunction with the silver catalyst. So here in this reaction we have proxy di sulfate reacting with silver ion here, it's going to be reduced which is why we have the electrons here as reactant. In the process we create our sulfate ion. And then here this represents our new oxidizing agent that can then react with another species in order to oxidize it. Now we're gonna say here that this oxidizing mixture can oxidize for example, manganese to ion to permanganate ion, it could oxidize Siri um three plus two serie um four plus. And that that shows you the power of this oxidizing agent mixture because syria represents one of the strongest oxidizing agents out there. But this ox Ilary oxidizing agent is so strong that it's even able to oxidize Syria. Now from there we also have our di chrome eight. Well here we're gonna have chromium being chromium three ions being oxidized to die chrome eight ion we have here, this is our then it'll cat ion and then we have VO two plus and this is just our vanadium for oxide. Cat ion. Now beside proxy di sulfate, we also have hydrogen peroxide which is H 202. It represents another powerful oxidizing agent. This one though, can work within an acidic or basic environment. Here in this general equation we have our proxy acid, hydrogen peroxide. Actually, hydrogen peroxide operating within an acidic environment. Again it's being reduced so that it can oxidize something else in the process of its reduction, it's going to be calm two moles of water as a liquid. Now in basic solutions it oxidizes Okay, so here in basic solutions it could oxidize cobalt to ion to cobalt three ion, It could oxidize iron to to Iron three, it could also oxidize manganese to ion to manganese for oxide. Now, if we switch it from a basic solution to an acidic solution, it now acts like an auxiliary reducing agent. So now it's going to reduce here, it could reduce die chrome eight ion into chromium three ion or it could reduce permanganate ion into manganese to ion. So it's more versatile than the proxy di sulfide sulfate because depending on the solution that it's in, it can act either as an auxiliary oxidizing agent and oxidize or can act as an auxiliary reducing agent and reduce. Now other commonly used oxidizing agents also include a silver oxide in organic. We tend to talk about silver compounds that act as oxidizing agents as tollins. Re agent for those of you who haven't taken organic, don't worry about it. For those of you who have taken organic, you might have forgotten just a little quick bit of outside information. And we also have sodium based which is an A. B. I. 03 as another special type of oxidizing agent. But out of these four peroxide dye, sulfate and hydrogen peroxide are the two most commonly referred to um auxiliary oxidizing agents. So remember when it comes to redox titrate asians, it's not uncommon to have your analyze exist in multiple oxidation states. So it's your responsibility to use either an auxiliary reducing agent or an auxiliary oxidizing agent to get that an elite down to just one single charge. Once we do that, we can then carry on with our redox tit rations. So just keep in mind the jobs of your auxiliary oxidizing agents versus your auxiliary reducing agents.

Analyte Oxidation State Calculations

So continue with this idea of oxidizing agents and reducing agents. Let's answer each of the following question questions based on the following half reactions from the half reactions that are given, we can see that they're all written as reductions. Where are electrons are written as reactant? Remember in a reduction your electrons are written as reactant and what we have here are all these cell potentials for each one of these half reactions. Now for the first one it's asking which is the strongest oxidizing agent. So let's think about what is oxidizing agent telling us Remember if you are the oxidizing agent that means that you have been reduced. If you've been reduced, that means you represent the cathode. And remember with the cathode we have the gaining of an electron And if you're gaining electron that means you must be on the same side as the electrons. And if you are the cathode you should have the largest self potential present. Since all of them are written as reductions. We can compare them all. If some were written as reductions and some were written as oxidation, you'd have to reverse all of the reaction. So they all are either written as reductions or written as oxidation. It's more customary to have them all written as reductions where your electrons are reacting. It's Now we can see here that the largest cell potential is with the first equation where the self potential is 1.36V. So we know that our ants will rely in the first half cell reaction and we're saying here you're gaining electrons, we're on the same side with the electrons if we look at our two choices, we have chloride ion or chlorine gas, it's the chlorine gas that's on the same side with the electrons. So that would be our answer. The strongest oxidizing agent prevent presented here would be the chlorine gas. Now it's asking us basically for the opposite, we're looking for the strongest reducing agent. So if you're the reducing agent, that means you've been oxidized. If you've been oxidized, you represent the anodes now remember the anodes should have the smallest cell potential. And remember if you're the anodes undergoing oxidation, that means you're losing electrons. Which means you won't be on the same side with the electrons because you've lost them be on same side with electrons. So if we take a look, the smallest one is the bottom reaction or talking about vanadium and our choices are either vanadium solid or vanadium two plus ion here. Again, we want to be away from the electrons. So the strongest reducing agent here would have to be the vanadium solid as my answer. So, these solid would be our answer for this question. Now, finally, it says will iodide reduce chlorine gas to chloride ion. Alright, so let's think about what it's saying. So here, so it's saying that iodide is reducing chlorine gas. So that means that I died would have to be oxidized. It's losing an electron and the electron that it's losing it's getting over to chlorine For to be oxidized, it would have to have it would have to be the an ode. It would have to have the smaller cell potential. So here the equation with iodine does have a smaller cell potential than the equation with chlorine. And if it's being oxidized, it would have to be on the side away from the electrons here. The iodide ion, Yes, it is on the side that is not next to the electrons. So my iodide ion would reduce my chlorine gas and as a result, become oxidized in itself. So here we'd say yes. So remember, for questions like this, you really have to go back and take a look and remember the principles that we've talked about in the past, leo the lion goes, if you're losing electrons, you're being oxidized. So you represent the reducing agent, things that are oxidized, or part of the anodes which have these smaller cell potential gain electrons reduction. So you're the oxidizing agent. If you've been reduced, you represent the cathode. The katha typically has the larger self potential. Remember this is true when we're dealing with a spontaneous electrochemical cell, when we're dealing with the galvanic or voltaic electrochemical cell. Those are spontaneous soul. The cathode should have the higher self potential and should have the smaller cell potential. When we're talking about non spontaneous electrochemical cells like the electrolytic cell, everything is reversed the cathode would actually be the smaller cell potential value. And the animal would be the larger cell potential value you'd be you'd be indicated which type of cell you're dealing with here. We're assuming that we're dealing with a spontaneous electrochemical cell, so we're dealing with a galvanic or voltaic cell.