Weak Base Strong Acid Titration Example

Jules Bruno
Was this helpful?
Ah Buffer contains 167.2 MLS of 0.25 Mueller Prepon OIC acid with 138.7 MLS of 0. Mueller sodium pro panna Wait. Now here it says find the pH after the addition of 150. MLS off 0.56 Mohler HCL here, the K of propane OIC acid is 1.3 times 10 to the negative five. All right, first of all, we know that propane OIC acid is an acid from the fact that acid is in the name. Next, we should know that it's a week oxy acid from the rules that we have learned before. And even if you don't remember those rules, we know it's a weak acid because it's K. A value is less than one. Remember, if an acid has a K less than one, it's a weak acid. If a base has a K be less than one, then it's a week base. So we have a weak acid here, sodium Prepon await looks similar to it, except it has one less hydrogen that has been replaced by a metal because it has one less hydrogen. This represents the conjugate base. Finally, we have HCL hydrochloric acid which is a strong acid. So you have two weeks species reacting with a strong acid. Remember, when we have a weak species reacting with a strong species, we have to set up in I C f chart Remember, in the I C F chart, whatever a strong has to be a reactant. So hcl here is the reactant because it is an acid, it will react with the conjugate base. So we write down the conjugate base Now remember, what is an acid do an acid donates h plus over to the base So we wind up getting as our products are propane OIC acid plus n a c l also remember now since we're doing an I C F chart, we only care about three things the weak acid, its conjugate base and whatever is strong. We have initial change final remember In a nice CF chart, we need moles as the units moles air is equal to leaders times more clarity. So we're going to divide the Emil's by then multiplied them by their mole Arat ease to get our moles here. We don't care about this compound. So when I take all the leaders, I multiplied them by more clarity. I'm going to get the most of each for my conjugate base. That would give me 0.583 moles For my strong acid, I would have 0.84 moles. And then for my weak acid, I would have 0.48418 moles. Now remember, look at Onley the reacting side. At this point, the smaller moles will subtract from the larger moles. So we're gonna subtract than by the smaller moles here, which comes from our conjugate base. So what I'm gonna have left at the end of zero conjugate base. I'll still have some strong acid remaining. Do the law of Conservation of Mass. Whatever happens on the react inside, the opposite happens on the product side. So I'm adding this many moles at the end of all of this. What do we have left? Well, we have a strong acid remaining and we have a weak acid remaining. Remember, when we're comparing them to one another, the strong ass will have a greater impact on the overall pH. So we're gonna focus on the strong acid, so we're gonna bring it down and find out what its concentration is. So we'll take the molds left of my strong acid here and divided by the total volume. What's my total volume? It's each one of these and leaders added up together. Okay, So take each one of those leaders, add them all up together on the bottom. So when we do that, we get our concentration of 0.563 Moeller for HCL at this point, realize that what do we have left? We have the concentration of a strong acid because it's a strong acid. I can simply take the negative log of the concentration and I'll have my pH. So take that concentration, which we just isolated and plug it in. And that gives us 1.25 as the pH for this solution. So remember, we're doing the same thing we've been doing. We're basically setting up our I c F chart. Whatever strong has to be a reactant, it will react with its chemical opposite because it's a strong acid, it will react with the conjugal base. From there, we determine What do we have left at the end To figure out what our Ph will be now that we've seen this example attempted to the practice question left on the bottom. If you get stuck, don't worry. Just come back and see how I approach that same practice question.