Arrange the solutions in order of increasing acidity. NaCl, NH4Cl, NaHCO3, NH4ClO2, NaOH

Video transcript

Hi, everyone. Welcome back. Our next problem says, arrange the solutions in order of increasing acidity. And our solutions are N AC LNH four CL NAHCO three NH four clo two and NAOH. And then our four, multiple choice answers are these solutions in four different orders. So we'll look at them more closely after we think about these solutions in their acidity, we have solutions of ionic salts and we want to think about our rules for what determines the acidity of these salts. So let's walk through each of these one by one and think about whether it will be acidic, basic or neutral. So we need to look at the ions in each case. So we start with our N AC our sodium chloride. Actually, I'm going to move that. So we look at our sodium ion and A plus and we recall that if the charge on our positive ion is less than positive three on a main group metal, it's neutral. So this has a charge of positive one. So it's a neutral salt for our chloride ion, we look at the conjugate acid, the conjugate acid. So we add a proton here, the conjugate acid, it is HCL, this is a strong acid and that means that our base, our chloride is a conjugate base. This is a neutral, an iron. So we've got neutral, neutral for sodium chloride highlight that so we can find that easily. Now, let's look at our next ion. Actually, I'm going to highlight the ion name too so we can find everything when we go back after looking at it through our notes. Now, our next ion here is NH four cl. So ammonium chloride. Well, the ammonium, the NH four here is a positively charged, I mean, and that makes that cat iron weakly acidic. And of course, chloride, we've already done that and we know it's neutral. So we highlight for ammonium chloride, we've got weakly acidic and neutral. So now we'll look at our next salt which is N A HC three or sodium bicarbonate for sodium we've already said is neutral bicarbonate. It's conjugate acid is carbonic acid H two co three, which is a weak acid. And therefore, this is a basic anion. So again, we've got our sodium bicarbonate, we've got a neutral cion and a basic anion. So let's look at the next one which is NH four CO2 or ammonium chlorite. I've already said ammonium is weakly acidic and now our chloride ion, its conjugate acid is chloric acid. Hclo two, don't mix this up with perchloric acid, which is a really strong acid. This is a weak acid. So that's going to give us. So that gives us a basic and I am. So here we can guess we'll have to figure out we've got a, a acidic cion and basic anion. So we kind of need to figure out which is dominant in order to be able to rank it with the other ones. So we'd want to compare the K A of our NH four plus ion to the KB of our chloride ion. So we need to look those up. So we do that and we find out the K A of our ammonium is 5.6 times 10 to the minus 10. The KB of our chloride ion is 9.1 times 10 to the minus 13. So RK A is larger, don't forget we have those negative exponents for ammonium, meaning for ammonium, it's going to produce more H plus as a product. So that means the acidic character of the salt is going to be dominant. So we'll just note dominant there. So I'm going to highlight my ammonium chloride. We know it's weakly acidic, which is the dominant character, but then it also has a basic, am I? So there's two sort of counterbalancing with acidic winning out. And then finally, our last is sodium hydroxide, which hopefully you recognize for now is an extremely strong base without even having to go through all of that and analysis. Soda hydroxy is one of those really recognizable strong bases. So now we need to arrange our solutions in order of increasing acidity. So going from most basic, we'll start with most basic two most acidic. I know it seems sort of silly to write that out when you say increasing acidity, but especially on a test, especially when you're in a hurry trying to keep in mind something like increasing acidity. It's really easy to write it backwards. So I kind of like to put it in like the most elementary terms to help me remind myself, what am I starting with? So I'm starting with the most basic and that's pretty obvious that's sodium hydroxide. So let's look for our answer. Choices that have sodium hydroxide. First choice A has the sodium bicarbonate. So that's incorrect. But then choices BC and D all start with sodium hydroxide. I guess they figure that's a, an easy one for us. So they're not going to help us out that way. So we've done our strong base. I'm going to put sort of a red X over that compound to remind myself I've already used it up. So what do we want to look for next? We want something. Maybe that's just basic like a basic anion and a neutral cion. Do we have that here? Well, yes, we do. Our sodium bicarbonate has a neutral cion and a basic anion. So that's going to be basic in character and that will be next. So let's look at choice B has sodium bicarbonate next. Choice C has sodium bicarbonate, but choice D has sodium chloride. So we eliminate choice D and I'm going to cross out my sodium bicarbonate. I've used that up already just so I don't have to keep looking back at those. I know what's left. Now, what's next? Well, we've got um one that's both acidic and basic with acidic dominating. We have a neutral, neutral and then we have an acidic neutral. So again, since we're going from most basic to most acidic, the neutral neutral will be next because our other two have an acidic character. So sodium chloride will be next in line. And Choice B has sodium chloride. Choice C has sodium chloride. So no new elimination there and cross off sodium chloride. Now we just have two left looking for the more basic of the two. Our ammonium chloride has the acidic cion basic anion with acidic dominating. Whereas ammonium chloride has an acidic cion and a neutral AM. So the ammonium chloride will be next because it has a more or a less acidic character than the other due to that basic AM. So let's look at choice B. Choice B has ammonium chloride next. So that's going to be incorrect and eliminate Choice B and we're gotten to our correct answer of choice C which indeed has ammonium chloride. Next. Following up with ammonium chloride, which has that weakly acidic cion and neutral anion. It's an even more direct comparison because they both have ammonium, they both have the same cion. But the ammonium chloride has this basic anion. While the ammonic chloride is a neutral. So very easy direct comparison there. So in order of increasing acidity, we have choice c sodium hydroxide, sodium bicarbonate, sodium chloride, ammonium chlorite and ammonium chloride can see you in the next video.