Hey, guys. In this new video, we're going to put to practice some of the principles we learned in creating a buffer. So for example, when it says, which of the following combinations can result in the formation of a buffer? So what we should realize here is in every example, we have 0.01 moles of hypochlorous acid. Now, hypochlorous acid, it says acid so we know it's some type of acid. It has oxygen so it's an oxyacid. And remember, if we do the math, 1 oxygen minus 1 hydrogen gives us 0 left over. So hypochlorous acid is a weak acid. So every single one of these is a weak acid. And because of that, you have to remember, what two ways can we make a buffer if we have a weak acid? So remember, the two ways is if we have a weak acid and its conjugate base. The second way is if we have a weak acid and a strong base. But in this second case, the weak species has to be higher in amount. So let's take a look at what's mixing with. Here we have NaOH which is a strong base. Here we have HCl which is a strong binary acid. Here, NH3 is a neutral amine, so it's a weak base. And NaOH again is a strong base. So we're looking for the weak acid to be paired up with the conjugate base or the strong base. So automatically, these 2 are out because we can't pair up a weak acid with a strong acid or a weak acid with a weak base. It has to be a conjugate base or strong base. Now, in the first one, we actually have more moles of the strong species, so this would not be a buffer. This would actually destroy the buffer. But for the last one, we have more of the weak species than the strong species. So it would be the last one that makes a buffer. So again, remember the 3 principles that we learned in creating a buffer. Apply them to this type of question.
Now for practice 1, I want you guys to figure out which one of these combinations will result in a buffer. Here, remember the word "of" means multiply. So if you multiply these two numbers together, you can help to find moles because remember, moles equals liters times molarity. So divide each of these by 1000, multiply it by the molarity to have moles. You could also keep it in milliliters and multiply times the molarity, but then that would give you millimoles. So I don't know if you guys want to deal with millimoles. It's basically the same thing but you don't have to do it that way. So divide them by 1000, the mL to get liters, multiply times the molarity to give you moles. Remember the 3 combinations that can result in the formation of a buffer. So check for each one of these. Look to see, do you have a weak acid and conjugate base? Do you have a weak acid and strong base? Or do you have a strong acid and weak base? Look for these combinations. If you don't see them, don't bother doing the math. So I would recommend looking at each compound first and seeing if they match up with any of these combinations. If they do, look more deeply. Look to see, does it help to create a buffer? If it doesn't match one of these three combinations, don't even bother looking at it. Don't do the math at all. And remember, one key thing I'll give you guys a hint, You have to make sure that you have the correct concentration of your strong bases. What did we say about strong bases? The concentration I give you is dependent on how many ions you have of which particular 4 ions. Doing that will help to get the correct answer. Once you're done with this, come back and click on the explanation button and watch me explain how to best approach this problem. Good luck, guys.