Protic Acids and Bases - Online Tutor, Practice Problems & Exam Prep

Acids are classified into two main types: binary acids, which consist of H⁺ and a nonmetal without oxygen, and oxyacids, which include H⁺, a nonmetal, and oxygen. Binary acids, like HF and HCl, often form from halogens, while oxyacids, such as phosphoric acid (H₃PO₄), arise from the hydration of nonmetal oxides. When acids neutralize bases, they produce salts, which can be acidic, basic, or neutral based on the properties of their cations and anions. Understanding these classifications aids in predicting acid-base reactions and their outcomes.

Acid Identification

Here we're going to say that the most common feature of an acid is that many possess an H⁺ ion. This ion itself can be called the hydrogen ion or the hydronium ion. Now, we're going to say here when it comes to acids, there are basically 2 major types that exist. Here we're going to talk about the first one. Here we have binary acids.

Binary acids where we have H connected to an electronegative element. Now, here we're going to say that these types of acids lack the element oxygen and they usually possess no metals. The most common type of these particular acids are the haloacids. From the name, we can tell that they're connected to halogens. Here we have HF, HCl, HBr, and HI.

Basically, in order to make them, these are from group 7. We have H⁺ and remember, group 7a elements, they all have a charge of minus 1. It's 1. So basically, that's how we got these halo acids. Now other types of binary acids that can occur as well, group 6.

So we have S^2-, Se^2-, Te^2-. They also can combine with H⁺ to give us binary acids. So here, the numbers are different within the charges, so they don't cancel out like the halo acids. They crisscross. This is H₂S which is hydrosulfuric acid, hydroselenic acid, hydro telluric acid.

These are some of the most common types of halo acids that exist. We also have other ones such as hydrocyanic acid. Then here you can have hydroazoic acid or azoic acid. These are most common types of binary acids that can exist. Just realize here that when it comes to binary acids, you basically have an H⁺ in front connected to a non-metal that is not oxygen.

We're going to say here, again remember, oxygen cannot be part of these types of binary acids and they usually contain no metals either. In the next video, you'll be able to see the second type of acids that are most common. Just click over to the next video and take a look at the second class of acids.

Acid Identification

Our second class of acids are known as your oxyacids. Your oxyacids just have H plus a nonmetal and oxygen. These two particular parts really form a polyatomic ion which is interacting with the H plus. For example, you have here H⁺ and then you have a phosphate ion. Once they combine, you have H₃PO₄.

That is phosphoric acid, an example of an oxyacid. If you have H⁺ with your nitrate ion, they combine to give you nitric acid. Now here, this is how the ions interact to form the acid but in reality, they are created by the hydration of nonmetal oxides. To form carbonic acid, we have the union of carbon dioxide gas and water. This is also an explanation of why if you leave tap water out or table water, or any kind of water in a glass long enough, carbon dioxide from the atmosphere will dissolve within it, making the water slightly acidic.

Here, to make sulfuric acid, we have the union of sulfur trioxide gas with water as a liquid. That's how we have the creation of oxyacids. Remember, an oxyacid is just H⁺ connected to a nonmetal and oxygen. You look for those three components and you have yourself an oxyacid. When it comes to acids, they either fit the binary acid model or the oxyacid model.

Now that we've seen that, take a look at the example down below. We know the 2 types of acids that exist and it's important to also remember that acids and bases contain some form of polarity. This is what allows them to interact in aqueous solutions with the donation or acceptance of H⁺ ions. So remember, we have oxyacids and binary acids, and they both have some level of polarity. Use that to guide you to the correct answer in the example below.

Come back and take a look and see how I answer that same exact question.

Acid Identification

So here it states, which of the following compound or compounds cannot be classified as an acid? Recall that we said acids fall into 2 categories. We have our binary acids and our oxy acids. Both types of acids contain some level of polarity. Now, if we take a look at the first one, we have H₂SE.

That's one of the examples we saw for binary acid. That is hydroselenic acid, so that is out. Next, we have HOCN. We have hydrogen, oxygen, and some nonmetals.

This there represents an oxyacid. And this is cyanic acid. Next, we have HN₃. That is also a binary acid we saw up above.
This is hydrozoic acid. Next, we have C₃H₈. This compound here is composed of only carbons and hydrogens. It is by nature nonpolar. Remember, the electronegative difference between carbon and hydrogen is very minimal.

So small, in fact, that we say it contains nonpolar bonds. This is a nonpolar compound, therefore it cannot represent an acid. Here, out of all the options, choice d would have to be the correct choice. Remember, when it comes to these types of acids, we have binary acids which are just H⁺ connected to an electronegative element. The most common electronegative elements are nitrogen, phosphorus, sulfur, or one of the halogens like selenium, tellurium.

Remember, binary acids do not contain oxygen and they usually possess no metals. Oxyacids are H⁺ connected to a nonmetal and oxygen. The nonmetal and oxygen in oxyacids are part of a polyatomic ion that is connected to the H⁺ ion. Remember these fundamentals when trying to describe the different types of acids that exist.

Ionic Salts

Here we're going to say that when an acid neutralizes a base, an ionic compound called a salt is formed. These solutions can be neutral, acidic, or basic depending on the acid-based properties of the cations and anions formed. So a good example here, we could have HF reacting with NaOH. So the compounds that we make are NaF plus water. NaF represents my ionic compound.

That is my ionic salt. Now this ionic salt is composed of a cation which is a positive ion and an anion which is the negative ion. We'll come back to this later on and see what kind of solution this ionic salt could potentially make. Now when we're taking a look at the ions, remember we have cations and anions. Cations are just the positive ions and we group them into 3 major categories.

We have here our transition metals, our main group metals, and our positive amines. Now here when it comes to transition metals, remember on your periodic table, those are the metals within the pit of the periodic table. We're gonna say here, if they have a charge of plus 2 or higher, then they will be classified as being acidic. If their charge is less than plus 2, then they are classified as neutral. Here we have titanium 2 bromide.

When it breaks up into its ions, it breaks up into titanium 2⁺ and Br^-. Again, we're only focusing on the positive ion for this point. Here, this is a transition metal. It's met the requirement of having a minimal charge of 2⁺. Because of that, this titanium ion is acidic.

Next, main group metals. These are metals from groups 1a, 2a, 3a, 4a, basically metals that are not transition metals. For them, they have to be plus 3 or higher in charge in order to be acidic. If they are less than plus 3, then they are neutral. Here we have gallium iodide.

Gallium's from group 3a which explains where this 3 came from. It's Ga³⁺ plus the 3 iodides. Again, we're not focusing on the negative ion. At this point, we're just focused on the cation, the positive ion that is formed. Here, gallium has met the requirement of having a plus 3 charge or higher.

Therefore, it is acidic. For our first two examples, this would help to create an acidic solution. Finally, we have here positive amines. Now amines, remember, are compounds that contain carbon, nitrogen, and hydrogen. So like example, Methylamine or Benzylamine, or they're compounds that contain just nitrogen and hydrogen like ammonia or the ammonium ion or hydrazine.

Now, we're talking about the positively charged ones. Here, positively charged amines are acidic. Here we have ammonium nitrate, It breaks up into the ammonium ion. This represents a positive amine because it contains just nitrogen and hydrogens. Remember, positive amines are automatically acidic.

Technically, here this NO₂ ^-, would be basic. But again, we're just focusing on the positive ion for this portion. Remember, an ionic salt deals with an ionic compound which is composed of a positive ion called a cation and a negative ion called an anion. At this point, we've looked at the requirements to determine if a positive ion is either acidic or neutral. Click on to the next video and see how do we gauge if an anion which is the negative ion is acidic, is basic, or neutral.

So anions can either be basic or neutral. And cations can be either acidic or neutral. So keep in mind the rules that we've covered in terms of a cation. Click on to the next video to take a look at anions.

Ionic Salts

So now we're going to take a look at anions. Remember, anions are your negative ions within your ionic salt. They can either be basic or neutral. Now here we're going to say, if we take a look at KF, it breaks up into K⁺ and F^-. We're going to say here to determine if this is a basic ionic salt, we're going to add an H⁺ to the negative ion.

So we add H⁺ to F^- to give us HF. We're going to say add an H⁺ to the anion and if you create a weak acid then your negative ion is basic. So here HF is a weak acid and because it's weak that means its conjugate base will be stronger. F^- is stronger so we can say it's basic. Now here we have LiBr.

So we break this up into its ions. Again, we add an H⁺ to the negative ion. But in this case, if you create a strong acid, which this is, that means that your conjugate base, the Br^-, is neutral. Remember, if you're strong one way, you're incredibly weak the other way. If you create a weak acid, that means you have a stronger conjugate base.

That's why it is basic. If you create a strong acid, that means you have an incredibly weak conjugate base, so weak that it is neutral. That's how we take a look at an ionic compound. Here if we were to go back up to our NaF that we got originally, we have Na⁺, which is a cation. It is a main group metal.

Remember, they have to be +3 or higher to be acidic; because it is not, it is neutral. When you have a neutral and you have a basic, that means your solution overall will be basic because neutral means we can ignore it. We'd say that NaF is a basic ionic salt. Now that you've seen cations and anions, click on to the next video to take a look at amphoteric species.

Ionic Salts

So amphoteric species are compounds that can act as an acid or a base. Now, when it comes to amphoteric species, they can be classified as being either acidic or basic. In this category, it's just important to remember which one we put in whichever category. Now, when it comes to acidic amphoteric compounds, remember what fits in this category are bisulfate HSO₄^-, bisulfite, and dihydrogen phosphate. Here, these are all acidic types of amphoteric species.

For our basic ones, we have bicarbonate, we have hydrogen sulfide ion, and then we have hydrogen phosphate ion. Again, remember, an amphoteric species can act as an acid or a base. This is seen by the fact that they possess hydrogens, so they can act as acids, but they also possess negative charges, so they can act as bases. But here, their grouping is really based on their Ka values. Later, when we take a look at diprotic as well as polyprotic acids and bases, we'll learn why exactly we classify some as acidic and others as basic.

Here’s what students ask on this topic:

What are the main differences between binary acids and oxyacids?

Binary acids consist of hydrogen (H⁺) and a nonmetal without oxygen. Examples include HF, HCl, and H₂S. Oxyacids, on the other hand, contain hydrogen (H⁺), a nonmetal, and oxygen. Examples include H₃PO₄ (phosphoric acid) and HNO₃ (nitric acid). Binary acids typically form from halogens or group 6 elements, while oxyacids arise from the hydration of nonmetal oxides. Understanding these differences helps in predicting their chemical behavior and reactions.

How do you determine if an ionic salt is acidic, basic, or neutral?

To determine if an ionic salt is acidic, basic, or neutral, examine the properties of its cations and anions. Cations can be acidic or neutral, while anions can be basic or neutral. For example, if the cation is a transition metal with a charge of +2 or higher, it is acidic. If the anion forms a weak acid when combined with H⁺, it is basic. The overall nature of the salt depends on the combination of these properties. For instance, NaF is basic because Na⁺ is neutral and F⁻ is basic.

What are amphoteric species and how are they classified?

Amphoteric species are compounds that can act as either an acid or a base. They possess both hydrogen atoms and negative charges, allowing them to donate or accept protons. Examples of acidic amphoteric species include HSO₄⁻ (bisulfate) and H₂PO₄⁻ (dihydrogen phosphate). Basic amphoteric species include HCO₃⁻ (bicarbonate) and HPO₄²⁻ (hydrogen phosphate). Their classification is based on their acid dissociation constants (K_a values).

How are oxyacids formed from nonmetal oxides?

Oxyacids are formed by the hydration of nonmetal oxides. For example, carbon dioxide (CO₂) reacts with water (H₂O) to form carbonic acid (H₂CO₃). Similarly, sulfur trioxide (SO₃) reacts with water to form sulfuric acid (H₂SO₄). This process explains why water exposed to air becomes slightly acidic, as CO₂ from the atmosphere dissolves in it.

What happens when an acid neutralizes a base?

When an acid neutralizes a base, they react to form an ionic compound called a salt and water. For example, HF (hydrofluoric acid) reacts with NaOH (sodium hydroxide) to produce NaF (sodium fluoride) and water (H₂O). The resulting salt can be acidic, basic, or neutral depending on the properties of the cations and anions formed during the reaction.