Acid Strength

So when it comes to binary acids recalled that binary acids are just when we have an H plus ion connected to an electro negative element, those electro negative elements typically are nitrogen phosphorus, sulfur, selenium, delirium or a halogen. Now we're gonna say here this is true for any acid, whether it's a binary acid or an oxy acid. We're gonna say here that strong acids are considered strong electrolytes. So that means that completely ionized in water. We show this by using a single error going in the forward direction. This illustrates that we make 100% of the ions here as products. So here we have hydrochloric acid which represents a strong binary acid when thrown into water, it completely dissolves into H plus ion and cl minus. What's really happening in actuality though is that the hcl is donating an H plus ion to the water and water itself is becoming a +30 plus and we're left with cl minus but H +30 plus and H plus are seen as being the same thing. They both represent hydro nea my on. But here we're just showing for simplicity sake that hcl is breaking down into H plus and cl minus. Now weak acids are considered to be weak electrolytes, Meaning they do not completely ionized when thrown into water. Here we have Hydrofluoric acid which represents a week binary acid here because it is weak, it does not completely ionized. So we don't have a solid arrow going forward. Instead, we have double arrows to show that an equilibrium has been established as a result. We're going to make much less than 100% of these following ions as products. And again, we have our acid, which donates an H plus over, and that's how we wind up with f minus ion and H +30 plus. Now that we've got down the fundamentals of what is a strong acid versus a weak acid, click onto the next video and see how exactly do we gauge the strength of any typical binary acid?

So when looking at the strength of any typical binary acid, it's based on two factors. The electro negativity of the nonmetal or the atomic size that it possesses. Now if we're looking at elements in the same period or row, then we look at electro negativity. So we're gonna say here the large um the more electro negative, so I'm just gonna abbreviate it as E. N. So the more electro negative, the more acidic, for example, let's say that you're trying to compare NH three, two ch four, two H. F. If we're taking a look at any typical periodic table. So we have here, boron, carbon, nitrogen, oxygen. And flooring here, we have basically hydrogen connected to a nonmetal. So we have hydrogen here connected to carbon nitrogen and flooring, they are in the same row with each other. And when it comes to electro negativity as we go from left to right, we're gonna say electro negativity, which I'm abbreviating as Ian increases. So the most electro negative out of these three would be H. F. Because flooring is more electro negative than nitrogen or carbon. So H. F. Would be more acidic than the other two. Now, when elements are in the same group or column, then we look at atomic size, we're gonna say here, the larger the atomic size which I'll abbreviate is a s than the more acidic. So let's here let's say here that we're comparing h F h B R H. I. So here we have chlorine bromine and iodine, they're all in the same column together as we go down, we're gonna say atomic size increases. So iodine is the lowest, down out of the choices in that column. Therefore H. I. Would be the strongest asset out of the three being compared. So that's how we take a look at different binary acids to determine which one is stronger. But let's say that you have assets that are not in the same row and not in the same column and you don't have a K. A. Chart where you can compare their K. S to one another. How would you determine which one is stronger? Well we're going to say here, if separated By one cop by one row. Look at electro negativity. So for example, let's say that you had to compare the strength of H. F vs H two s. E vs Let's say H two s. Actually. So here you're going to say based on this periodic table you have flooring here and sulfur here, they're separated from each other by just a row. So we look at electro negativity, flooring is more electro negative than sulfur because as we go from left to right and up a group electro negativity increases. So this would be stronger If separated by more than one group By more than one row. Look at atomic size. So let's say you're comparing H. F versus H two S. E florin is still here and they're separated by more than a row because Florence in row two selenium in row four. Right? So as a result of this we look at atomic size as we head downwards in groups, the size increases. Okay, so as we're going down a group of size increases and as we go, yeah as we go down we'll just say as we go down, atomic size increases. So here selenium is larger than flooring. Therefore H two S. E. Is a stronger acid than H. F. So again it can be kind of tricky when it comes to binary acids. But first you say, we're looking at electro negativity or atomic size if they're in the same roar period, we look at electro negativity if they're the same column or group, we look at size. If they are separated from each other by just a row, then we look at electro negativity. If they're separated by more than one row from each other, then we go and look at atomic size. So these are the different criterias. We used to compare different binary acids. Of course if you're given a K. A. Chart, you can just compare their K values. In that case you just say the larger K. A is a stronger acid. This approach should only be used if you don't have K values for your given binary acids. Now that you've seen this look to see if you can figure out the answer To example one come back and see how I approach that question

So for this example question it says which is the weakest acid from the following. So we have H. Two S. H. F. And H. Two T. So if we take a look at our periodic table and let's just erase all of this here. We have hydrogen connected to sulfur flooring and delirium. So those are the elements we're looking at. So florian is here, then we have sulfur here and then solarium down here we're gonna say remember sulfur and flooring are just separated from each other in terms of one row. When you're separated by one row we look at electro negativity. Flooring is more electro negative than sulfur. Therefore H. F. Is a stronger acid than H. Two S. But remember we're not looking for the strongest, we're looking for the weakest. So this is automatically stronger than this. So this is out now we have to compare H. Two S. Two H. Two T. E. They're both in the same column or group. Remember when you're in the same group we look at atomic size as we go down a group, the atomic size increases and therefore the acidity increases. So H. Two T. E. Which is hydrochloric acid would be the stronger acid. So this is out. So that means out of the three choices hydro sulfuric acid would have to be the weakest binary acid here. D wouldn't work because we know that they don't have the same acidic strength. So remember recall all the tips and and hints that we talked about in terms of comparing binary acids to one another based on the concept of electro negativity and atomic size. Now that you've seen example, one finish it off by looking at example to try it out on your own and then, once you're done, come back and see how I approach that same example to question.

So now it's time to put everything together in this one, it says which of the following acids would be classified as the strongest. So here we're looking at hydrogen connected to carbon, nitrogen, oxygen flooring and phosphorus. So we look at our periodic table, so we're connected to carbon nitrogen oxygen flooring and phosphorus. Alright, so we know we hear that if you're in the same column then we look at atomic size. So here P. H. Three Is lower down, so it has a greater atomic size. Therefore it's a stronger acid than NH three. So this is out, phosphorus is one row away from all the other elements. Therefore we're gonna look at electro negativity in terms of electro negativity, phosphorus is not the most electro negative element here. The most electro negative element is flooring. Therefore H. F. Happens to be the strongest asset here, out of all my choices. So again, remember, we're looking at the ideas of electro negativity and atomic size when comparing the strengths of different binary assets to one another. If you don't have the K values for your given binary acids, this is the approach you need to take in order to determine which one is the strongest or weakest from the list provided

now recall that an oxy acid is composed of an H. Plus ion connected to a nonmetal plus oxygen. That non metal and oxygen is usually in the form of a poly atomic ion. Now we're going to say the strength of oxy acids is based on the number of oxygen's contained within the acid or the electro negativity of the non metal. Now here, if we don't have a K. Value and we need to determine if an oxy acid is weak or strong, then we can just follow this one simple rule. Now we're gonna say if my oxy acid has two or more oxygen's then hydrogen, then my oxy acid is classified as a strong acid. Now again, we can use this rule whenever we don't know what the K. Value is for a particular oxy acid. But if we have a strong oxy acid, remember a strong oxy acid would have a K. Value. That is much greater than one and it would have a P. K. Value. That is negative. Okay, so that would classify as a strong oxy acid. But if you don't have those pieces of information, we rely on this rule here. Now here, we're looking first at this first oxy acid. So this is cleric acid. It has hydrogen, a non metal and oxygen. That's why it's classified as an oxy acid here we have three oxygen's involved and one hydrogen. So three oxygen and one hydrogen. When we subtract those, we need a minimum of two oxygen's remaining here, we have a minimum of two oxygen's remaining. So this would be a strong oxy acid. Next H O C N. This is also an oxy acid. It has hydrogen, oxygen and non metals. Here we're gonna look at the number of oxygen's which is one number of hydrogen is which is one. So at the end we have nothing left here. This would be a week oxy acid because it hasn't met the requirement of having a minimum of two oxygen's remaining. Then finally here we have H C four H 702. Here we have two oxygen's and we have eight hydrogen. We need a minimum of two oxygen's remaining here. We don't have any oxygen remaining. We have an excess of hydrogen. So this is classified as a weak oxy acid. So again, if you don't have a K. Value or PK value associated with your oxy acid, you can rely on this rule. Later on, we'll look at the exceptions that reside in terms of certain oxy acids. Uh that break this one rule for now, click onto the next video as we continue by comparing different oxy acids to one another.

So when we're comparing oxy acids to one another, we're gonna say when comparing the strengths of different oxy acids. Remember if they have different number of oxygen's then the more oxygen's, the more acidic. So for example, let's say you were comparing H barrel four vs HCL. here We have four oxygen's -1 hydrogen. So that's three oxygen's left Here, we have three oxygen's -1 hydrogen. We have two oxygen's left. So the net difference is this one has more oxygen remaining, therefore it's a stronger oxy acid. What if they have the same number of oxygen's though? What do we do then? We're going to say, well if they have the same number of oxygen's then the more electro negative, the nonmetal the more acidic. So let's say we're looking at HBR 04 vs HCL 04. In that case they both have a net loss of of one oxygen. When we subtract oxygen from hydrogen. So they have three oxygen's left of peace. We look at the electro negativity of the nonmetal. Remember electro negativity increases going from left to right and a decrease is going down a group. So we have flooring, chlorine bromine and iodine here chlorine is more electro negative because it's higher up than browning. Therefore, since chlorine is more electro negative, Hcl four is a stronger stronger oxy acid than H B R. 04. So again, to compare them, we look at first the number of oxygen's the one with the most oxygen's remaining is stronger if they have the same number of oxygen's, then we look at electro negativity of the non metal. The more electro negative one will be the stronger oxy acid. Now that we've been able to compare them. Click onto the next video, where we actually see some exceptions to the rule in terms of the in terms of looking at the strength of oxy acids.

So when it comes to our oxy acids, remember we have our rule when we have two or more oxygen and hydrogen that's classified as an oxy acid. Now there are exceptions to this rule here, we have three major exceptions we have here oxalic acid we have here I OTIK acid and then this here is just a place holder holder that represents AmFA Terek species. Now here when we do the math we have four oxygen's two hydrogen. So we have two oxygen's left and same thing here we're gonna have to oxygen's left. Now. Based on our previous rule, we will think that oxalic acid and biotic acid would be classified as strong oxy acids. But in fact they are weak. They are weak because the electro negativity of the carbon and iodine is here are not significant. They're not electro negative elements. Therefore, overall the strength of these oxy acids are weak. Okay, so both of these would be weak oxy acids that have K values less than one. Now am philatelic species. Um they can act as acids or bases acids because they contain hydrogen and basis because they have that negative charge there. These are not this is not the only one remember we saw in previous pages we had by cell fight, we had um bicarbonate, we had di hydrogen phosphate, hydrogen, phosphate as well. These ample Terek species because they can act as acids or bases. We can't say that they are definitively strong oxy acids. So we would say that here they would also be weak. Now just recall the infotech species that I said that we're acidic and the ones that I said that were basic to help guide you determine what the true nature of that Anfo Terex species is. So remember guys, we have the rules for oxy acids. It's just that these three are exceptions to that rule now that we've seen that try example that's left on the bottom of the page and see if you can get the correct answer once you do come back and take a look at how I approach that same question.

So here we are asked to rank the following oxy acids in terms of increasing acidity. Alright, so what we need to do first is we need to compare the number of oxygen's found within each oxy acid. So we look at how many oxygen's we have when we subtract it by the number of hydrogen is to find out the net remaining amount of oxygen's. So we have three oxygen's here minus one hydrogen. So we have two oxygen's left Here. This would have two oxygen's -6 hydrogen. So we have four hydrogen is left Here, we have three oxygen's -2 hydrogen. We have one oxygen left. And then here we have three oxygen's -1 hydrogen. So we have two oxygen's left. Remember the more oxygen's remaining, the stronger the oxy acid, we want to do it in terms of increasing acidity. So the weakest one would be option B because that one doesn't have any oxygen remaining, then we'd have C. Because it only has one oxygen remaining A. And D have the same number of oxygen's left. Remember when the number of oxygen's left are the same. We look at electro negativity of the nonmetal to determine which one is stronger. So here we have to compare the electro negativity of nitrogen to chlorine. So nitrogen is here and chlorine is here. So remember as we go from left to right, electro negativity increases and as we go down A group, it decreases since chlorine is more to the right chlorine is more electro negative than nitrogen. Therefore clark acid here would be a stronger acid. So we'd say here, A and then D. So this would be the proper order of increasing acidity, where we're going from the weakest oxy acid to the strongest oxy acid.