Binary Acids - Video Tutorials & Practice Problems

Binary Acid Formation

Hey, everyone. So here we're going to say that binary acids represent covalent compounds containing the H plus ion bonded to a nonmetal anion, not including oxygen. OK. So binary acids are acids that do not possess oxygen within themselves. So if we take a look at two typical types of binary acids, let's look at H plus connecting to BR minus. Remember when the numbers are the same in terms of their charges, they just simply cancel out. So our acid here would be H pr which is hydro brom acid. And then here let's do H plus connecting two sh minus. Again, the numbers are the same, they just simply cancel out. So this becomes H two S this is representing hydrogen sulfur hydro sulfa acid, right? So here we have two typical types of binary acids. So remember when we're looking at a binary acid, it does not possess oxygen.

Binary Acids Example

Which of the following represents the possible structure of a binary acid. Remember binary acid is an acid that does not contain oxygen. If we take a look at the first one, we have a covalent compound beginning with the hydrogen. So yes, it is an acid but the presence of oxygen means it is not a binary acid. The next one isn't an acid at all. It's barium chloride, there's no H plus ions anywhere. The next one we have is HF it's covalent, it starts with a hydrogen. So it's an acid, it has no oxygen. So it is a binary acid. This is Hydrofluoric acid. Then finally, we have lih. Now here this is an ionic compound and more importantly, it is a metal C ion connected to a basic anion. It is L I positive H minus. This is an example of a base. Now, if you didn't see that, make sure you go back and take a look at my videos where I talk about bases and the introduction of them. So here this would be a base out of all the choices. The only one that is a binary acid is option C

Binary Acid Strength

Now that we know how to identify binary acids. Let's talk about their strengths. We're gonna say that our halo acids or Halo aids. Well, they're the only strong binary acids that exist and involve an H plus ion attached to a halogen. Remember your halogens are your group seven A elements. And the most important halogens on the periodic table are fluorine, chlorine, bromine and iodine. Now of these, the strong binary acids are hydrotic acid, hydro acid and hydrochloric acid. So those would be H I HBR NHCL, which would be these three here. Notice that I have not included fluorine. That's because Hydrofluoric acid represents a weak binary acid. We'll talk about that later on on why it's considered a weak binary acid and the other three are considered strong. Now, recall also that strong acids represent strong electrolytes and weak electro, weak acids represent weak electrolytes. We're gonna say here that strong acids dissociate or ionize completely in water. And we're gonna say that they donate a proton easily. When we say proton here, we're talking about the H plus ion. We're gonna say that weak acids only partially dissociate, our ionize it donates a proton less readily, so, not as easily and it favors reactants, meaning it doesn't really wanna break up into uh ions too much or rather stay in its molecular form. Here, we have an example of hydrochloric acid and hydro cyanic acid. Both of these are binary acids. Hydro cyanic acid is one of our strong halo acids. It breaks up 100% into H plus ions and cl minus to illustrate this, we use a solid arrow going forward. And we're gonna say, since it's a strong acid, it dissociates completely, which we see in the form of these two ions, it easily donates an H plus. In reality, it's donating this H plus to the water that surrounds it. We'll see later on on how that works. And then we are making 100% of both of these ions. So basically, all of this is gone, the strong HCL is completely ionized, it's gone. It's all been transformed into the ions. So it favors the product side. For our weak acid, we have hydro cyanic acid HCN. So if it's a weak acid, we're gonna have the use of two arrows, we're going to have a larger arrow moving backwards and we're gonna have a smaller arrow moving forward. And so you can show it like this or you could show it like this, both are correct. And what this is showing me is that the larger arrow, what's going, which is going in the reverse means that the reverse direction, the reaction side is more greatly favored. The smaller arrow moving forward means that very little of these two ions are produced. So we're gonna have less H plus and CN minus ions being produced. So HCN dissociates partially, meaning there's gonna be more molecules of HCN than there are ions of H plus and CN minus less readily donates protons. So HCN doesn't easily give away an H plus to the water. And again, the larger arrow is pointing towards the reactant. So the reactant side is more greatly favored. So keep this in mind when we're talking about the strengths of binary acids.

Binary Acids Example

The following represent aqueous acid solutions. So identify the strong acid, the weak acid and the weakest acid. So here we have H A as the general formula for or generic formula for an acid. Here, when it breaks up, it gives us H plus ion and A minus. I, we're told that H A is in this form, H plus would be this smaller H plus ion A minus would represent this larger uh gold sphere. Now, if you are a strong acid, you completely ionize, you make 100% of these two ions. So you should have none of this remaining. If we look at our options, which one shows that. Well, if we look, it's the middle one, the middle one, we have only these two, there is none of this hanging around. So this represents our strong asset. The other two are weak because we have a lot more of the acid intact than we do ions being produced. But we have to identify which one is weak and which one is weakest. So if we take a look here, let's try to look at how many we have of each. We have 12345677 of these has for the first one. And then how many H pluses do we have? We have two H plus 12 and then two A minus 12. What about over here, over here we have 1234567899 has and only one H positive and one A minus. So we can see there's a lot more of the acid intact. So very little of it has broken up. So this would have to be our weakest acid because it dissociates or ionizes the least. And then this one will be a weak acid. So that's how we look at and depict each of these aqueous acid solutions. Remember it all hinges on the fact that an acid, if it's strong, completely ionizes or dissociates into ions. A weak one, only partially dissociates, the less it dissociates, the weaker the acid will be.

Comparing Binary Acid Strength

Well, we know there are three strong binary acids, Hihbr and HCL. And we still need to know how to compare binary acid strengths nonetheless, because you could be asked to compare the strengths of two strong binary acids or to compare the strengths between weak binary acids. How exactly would we do that? Well, we're gonna say here that the strength of binary acids is based on the electronegativity or atomic radius of the non hydrogen element. So if we take a look at a typical periodic table, we're looking at electron negativity. So as we go from left to right on the periodic table, electron negativity abbreviated en would increase. And if we go down any group, we're going to say that atomic radius abbreviated A R would also increase. OK. So these are the directions that allow these two periodic trends to increase. Now, how does this relate to the strength of binary acids? We're gonna say here when comparing the strengths of binary acids, if the elements are in the same period or row, then use electronegativity electron negativity to compare their acid strengths. So here we're going to say the greater the electronegativity of the non hydrogen element than the more acidic the acid, if elements are in the same group or column, then use atomic radius. In order to compare their acid strengths, you are going to say that the greater your atomic radius then the more acidic your acid, right. So these are the concepts, periodic trends we're going to use to compare the strengths of different binary acids to one another.

Binary Acids Example

Which is the weakest acid from the following. So here we have HFHCLHIH pr or all are equal. If we look at the periodic table, remember we're looking at the non hydrogen element found within the binary acid. So we need to compare fluorine, chlorine, bromine and iodine to one another. When they're in the same group. Remember when you look at atomic radius and we say the higher the atomic radius, then the more acidic the acid, if we look iodine would have the largest atomic radius out of the four elements as a result of this H I would be the strongest acid. But here we're looking for the weakest, the one with the smallest atomic radius would be fluorine. So HF would be our weakest acid. So here option A is the correct answer.

Binary Acids Example

Now there will come times when we're comparing binary acids and they're not found within the same period or row or not found within the same group or column. So what exactly do we do? Well, we're going to say that if the binary acids are separated by one period, then use electronegativity to compare their acid strengths. If separated by more than one period, then use atomic radius to compare their acid strengths. If we take a look here at this example, question it says, which is the weakest acid from the following. We have H two sehfh two teh two s or they're all equal. We have to look at the non hydrogen element of the binary acid. So we are comparing selenium, fluorine, teum and sulfur. We want the weakest acid here. All right. So if we take a look, we're going to say that sulfur, selenium and tum are all within the same group. Since they're all within the same group, we look at atomic radius, the larger the atomic radius, the stronger the binary acid. So H two T would be stronger than H two se H two sc would be stronger than H two S. So these two are out, since they're both stronger than H two S, we know that they couldn't be the weakest as. So that means we now have to compare HF versus H two S. So how do we determine which one is weaker? Well, we're gonna say here, if binary acids are separated by one period, then we look when we use electron negativity to compare their acid strengths. Fluorine is in the second period. Sulfur is in the third period. They're only separated by one period from one another. If we look at electron negativity, fluorine is more electron than sulfur fluorine is the most electron element on the periodic table. So that would mean that HF is more acidic than H two S. So by process of elimination, option D would be the best answer. It is the weakest acid out of all the options given.

Which of the following acids would be classified as the strongest? 

a) CH₄                          b) H₂Te                         c) H₂S                           d) PH₃                          e) BH₃

• A. CH₄
• B. H₂Te
• C. H₂S
• D. PH₃
• E. BH₃