Standard Reduction Potentials - Video Tutorials & Practice Problems
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concept
The Standard Reduction Potential
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In this video we're gonna take a look at an old concept of oxidation and reduction, and now combine it with a new variable, our standard reduction potential. Here its variable is e naught or 0, and then red for reduction. Here it's a tendency of a species to gain electrons from another species. We're gonna say recall that reduction is the gain of electrons, while oxidation is the loss of electrons. Since it has this not here, we're going to say that standard reduction potentials values are measured at standard conditions. Standard conditions means our temperature is 25 degrees Celsius, our pressure is 1 atmosphere, our molarity or concentration is 1, and our pH is equal to 7. We're going to say that the higher your standard reduction potential value, then the more likely reduction will occur. Now that we've compared our old concepts of oxidation and reduction to our new concept of standard reduction potentials, let's take a look at comparing different elements and compounds and their given standard reduction potentials.
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concept
Comparing Standard Reduction Potentials
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Here in this image we have different types of elements and they're given standard reduction potentials. So here we can see that they're represented as half reaction, reduction half reactions. And we know they're reductions because if we were to calculate the oxidation numbers, let's say for fluorine, here it's in its neutral state, so it's 0, and now it has a charge of minus 1, so each fluorine is now minus 1. The oxidation number decreased, so we know that this represents a reduction. Another helpful way to remember that these are reduction reactions is that the electrons are reactants, so electrons as reactants equals reduction, so r with r. Here we can see that our fluorine F2 gas has the highest reduction potential, and in this list we see that lithium has the smallest. Now we will also see that we have 2 H+aqueous, plus 2 electrons gives us H2 gas. It has a standard reduction potential of 0. This kind of acts as our border, and we can compare the strength of reduction potentials on whether they're above 0 or below 0. Here, we're going to say that this is our border. It also has its own unique name. It's called the sheet. Now that stands for standard hydrogen electrode. Now recall we said that the higher your standard reduction potential is, then the more likely reduction will occur. So here we see that f 2 has the highest standard reduction potential, so it wants to be reduced more than anything else. Now if you are a if you're being reduced, what kind of agent would you be? Well, remember, if you're being reduced, that means you're the oxidizing agent. Here we're going to say as we go up this group, the ability to be reduced increases, and therefore, the strength of being the oxidizing agent also increases. Because remember, oxidizing agent is tied to reduction. If reduction is going up, being an oxidizing agent is also going up. Conversely, if we look the opposite way, we're saying if we go down the list, then our standard hydrogen or standard reduction potentials are getting smaller. If they're getting smaller, you're less likely to do reduction. You're more likely to do oxidation. And remember, if you're being oxidized, that means you're the reducing agent. So we're gonna say, going down the list, you're gonna say oxidation more likely. So your strength of being oxidized is increasing, and therefore your strength of being a reducing agent is increasing. Okay. So here, that's what we can say in terms of this chart. So going up the list, the numbers get bigger, so reduction is more likely, and therefore you're a stronger oxidizing agent. Going down the list, your standard reduction potentials get smaller, so oxidation is more likely, and therefore you're a stronger reducing agent. So keep this in mind when looking and comparing the different types of standard reduction potentials of different elements.
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example
Standard Reduction Potentials Example
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Here it says, determine which of the following will least likely donate an electron. So if we're talking about something donating an electron, that means that it itself is being oxidized. Okay? So they're saying least likely to donate an electron means least likely to be oxidized. Because remember, how would I be able to donate an electron? I have to give it up. Oxidation means we're losing electrons. We're donating them to our other species. So here we have h 2br2zinc 2+inc ion, chloride, and Li+. So the one that's least likely to be oxidized means the one that is more likely likely to be reduced. So when we say the one that's most likely to be reduced, what does that really mean? Well, in relation to our reduction potential, it'd be the one with the largest e value. So one with our largest standard reduction potential. We take a look here, we have h 2. We know that that forms our boundary, so that's at 0 volts. We have b r 2 here, which is at 1.09 volts. We have zinc, which is related to this 0.76 volts. Chlorine is 1.36 volts, and then we have lithium, which is way down to the bottom at negative 3.04 volts. The one with the largest standard reduction potential, which means it's more likely to be reduced and least likely to be oxidized, would have to be cl 2. So here, our answer would have to be option d. So option d, CL 2 would be our final answer.
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Problem
Problem
Rankthe given metal ions in order of increasing strength as an oxidizing agent.