How are standard reduction potentials defined?

Video transcript

Welcome back, everyone. Which of the following statements correctly describes standard reduction potentials and we're given for answer choices. So let's analyze each answer starting with A, they are a measure of a chemical species tendency to lose like can be oxidized. According to the name, we're looking at the standard reduction potentials. And according to the Mnemonic Oil rig, we know that reduction is gain, oxidation is loss, reduction is gain. So statement A is incorrect because we are looking at a measure of a chemical species tendency to gain electrons and be reduced because as the name suggests, that's the standard reduction potential. So A is incorrect. Now, what about B? Option B states that they are always measured at? No, were under non-standard conditions, right? So if we look at the name once again, that's a standard reduction potential. Meaning we cannot have non-standard conditions, we are looking at standard conditions, standard conditions would be 25 °C and one atmosphere pressure. So whenever we are looking at standard reduction potentials, we want to also have standard conditions, non-standard conditions would allow us to get the cell potential at non-standard conditions. So option B is also incorrect. We want to have standard conditions, option C states that they are defined relative to the standard hydrogen electrode set at a potential of zero volts. So this is correct. Let's recall that specifically we're looking at a reduction of two H plus combining with two electrons to produce hydrogen gas. And this is measured at zero volts. We can see that from the tables, right. And this is exactly what we're looking for. So answer choice C is the correct answer to this problem. What about option D? Out of curiosity, we can look at D, it says a low protection potential indicates a greater tendency to be reduced. Now, this is incorrect. Let's understand why we have to recall that the greater the E knot value, the higher the tendency to be reduced because E not itself defines the reduction potential. We can see that from the name. So the greater the value, the higher the tendency to be reduced and not the opposite. When it gets more negative, we then a lower tendency to be reduced. So option D is incorrect and we can say that option C is the correct answer to this problem. Thank you for watching.