Naming Acids - Online Tutor, Practice Problems & Exam Prep

An acid is a covalent compound that typically begins with a hydrogen ion (H⁺), forming hydronium ions in solution. Acids can be classified into binary acids, which consist of hydrogen and a nonmetal anion without oxygen, and oxyacids, which contain hydrogen and a polyatomic ion with oxygen. Naming conventions include using "hydro-" for binary acids and changing the suffix of polyatomic ions from "-ate" to "-ic" and "-ite" to "-ous" for oxyacids. Understanding these classifications and naming rules is essential for mastering acid-base chemistry.

Naming Acids

Before we start naming acids, let's first talk about what exactly is an acid. Now, an acid is usually a covalent compound beginning with a hydrogen ion. So, the hydrogen ion in this case is H⁺. Another name for this hydrogen ion is called the hydronium ion. Now, going back to covalent, what exactly is meant by covalent compound? Well, a covalent compound is a compound that contains only nonmetals bonded together. If you don't remember who the nonmetals are, make sure you go back and take a look at my videos on the periodic table and the classifications of the elements that lie within it.

If we take a look here, some common types of acids, all of them are covalent because all of them possess nonmetals together. And since they're all covalent, we also see next that they all begin with hydrogen. That tells us that they all represent acids. So HCl, HNO₂, H₂SO₄, we see that some of them are pretty simple like HCl and some of them are pretty complicated like H₃PO₄. We'll talk about the different types of acids later on and the rules associated with naming them. Now, remember, we said that they usually begin with the hydrogen ion. Usually does not mean always. And with chemistry, you're going to see that exceptions do pop up here and there. A good exception to this is acetic acid.

Acetic acid can be drawn in two different ways. The first way goes along with the definition we have. It starts with the hydrogen and it's covalent because it only has nonmetals. But another way to write acetic acid is CH₃COOH. In this case, the hydrogen ion is actually written in the back. This is an exception to our definition, where this is still an acid, but it doesn't begin with the hydrogen ion. Now that we know the basic structure of an acid, let's move on to some videos and let's tackle the different types of acids that exist and the ways of naming them.

Naming Acids

So here, let's take a look at binary acids. Now binary acids, since they're acid, they are also represented as covalent compounds and they're going to contain the H⁺ ion, which is our hydrogen ion. But here they're going to be bonded to a nonmetal anion that is not oxygen. So binary acids are covalent compounds, usually beginning with hydrogen, that contain no oxygen. Here, how do we form them? Well, we know that they possess the H⁺ ion, and let's think of a nonmetal they can be connected to in the anion form, which means they have a negative charge. So let's say we're dealing with iodine. Iodine is in group 7A, so its charge is minus 1. So here we have plus 1 from the hydrogen, minus 1 from the iodine. If you've seen our videos on writing ionic compounds, we apply the same principles here. Remember, if the numbers in the charges are the same, they simply cancel out and you combine together your elements. So here, this would be HI. HI would represent a typical binary acid. Alright. So here, rules for naming these binary acids. Well, step 1 is the prefix they're going to use. The prefix they use is 'hydro,' and that basically represents the H⁺ ion. And then we're going to say step 2, use the base name of the nonmetal. Now here's the thing. Remember, the base name is usually the beginning part of the name of the nonmetal that is being used and it's unchanged, except when we use sulfur or phosphorus. So in their acid forms, for sulfur, we actually use the entire name. We don't use the base name. We use the entire name for sulfur. And for phosphorus, we don't just use its base name, we use a little bit more. The base name of phosphorus is 'phospha,' but in acid form, we actually use 'OR' as well. So, again, the nonmetal part of the acid, that is not the H⁺, we use its base name except for sulfur and phosphorus. We use a little bit more than just their base names. Then finally, to end the name of the binary acid, we use 'ic acid' for the end of the name. So we apply these principles and we'll be able to name any type of binary.

Naming Acids Example 1

So for this example question, it says write the formula for each of the following compounds. We have hydroiodic acid, hydroselenic acid, and hydrofluoric acid. Alright. So we're going to say that hydro, we know that represents the H⁺ ion involved, so we have H⁺ for all of these. Since they're all binary acids, we know they all end with -ic acid. What we look at is the base name. The base name tells us the nonmetal involved. Iode means we're dealing with iodine. It's in group 7a, so it's minus 1. Selenium. It's in group 6a, so it's, 2 minus or minus 2. And then fluor means we're dealing with fluorine which is a group 7a, so it is minus 1. Now for the first one, for a, remember, when the numbers and the charges are the same, they simply cancel out and you combine your elements together. So hydroiodic acid is just HI. And then also for c, plus 1, minus 1, the numbers are the same, so you just combine them together. So hydrofluoric acid is HF. For b, hydroselenic acid, we have here different numbers in the charges. Remember, when the numbers are different, they crisscross. So one from here comes here, 2 from here comes here, so that means, hydroselenic acid is H₂Se. If you don't quite remember these rules, make sure you go back and take a look at our videos talking about writing ionic compounds. It's the same kind of principles behind this. We look at the ions, the charges, if the numbers are the same, they simply cancel out. If the numbers are different, then they crisscross. Using this helped us to determine each one of these 3 binary acids. Now that we've done this example, move on to the next video where we take a look at a practice problem.

Give the systematic name for the following compound:H₂S

• A. sulfuric acid
• B. hydrosulfuric acid
• C. sulfic acid
• D. hydrosulfic acid
• E. hyposulfuric acid

Give the systematic name for the following compound:HCN

• A. cyanate acid
• B. cyanous acid
• C. hydrocyanous acid
• D. cyanic acid
• E. hydrocyanic acid

Naming Acids

When it comes to oxyacids, oxyacids represent our second type of acid. Now, we're going to say they represent covalent compounds because they're acids, they contain a hydrogen ion as well, but now they're bonded to a polyatomic ion containing oxygen. And it's pretty clear why that is because the name is oxy, highlighting the fact that we have oxygen present now. So, how could we form an oxyacid? Well, here we have our H⁺ ion, so H⁺¹, and let's just think of a polyatomic ion that possesses oxygen. Here, we could have NO₃⁻. NO₃⁻ is our nitrate ion, and remember, when the numbers in the charges are the same, they just simply cancel out, and you combine together your elements. So HNO₃ would represent an oxyacid. It is covalent because it possesses only nonmetals. It has your hydrogen ion at the beginning of the compound structure, and altogether we have our oxyacid. Now that we know how they're formed and what they represent, click on to the next video and let's go over the rules for naming them.

Naming Acids

When it comes to naming oxyacids, it's first important to remember your polyatomic ions. Now, if you don't remember your polyatomic ions or you haven't watched my videos on them, I suggest you pause this video and go back and take a look at those videos first. Then come back and we can tackle naming oxyacids together. Alright. So for those of you who are ready, let's go. We're going to say here rules for naming oxyacids. Rule 1, if the polyatomic ion ends with -ate, then change the ending when it's in its acid form to ic acid. Here, we have a memory tool that'll help us. So here we're gonna say I ate in acid, and it was icky. Now, don't go biting into acids or eating them in any way, but just remember that -ate goes with icky. Okay? So in its polyatomic ion form, it's -ate, but in its acid form, we change the ending to ic acid. So here we have H+NO3-. Remember, NO3- is your nitrate ion. When I combine them together to give me HNO3, that is our oxyacid form. Here, the -ate ending changes to ic acid. So nitrate becomes nitric acid. But remember, we also have polyatomic ions that end with -ite. What do we do in those situations? Well, we're gonna say if the polyatomic ion ends with -ite, then in its acid form, we'll change the ending to ous acid. And again, we have a great memory tool, so I only bite into things that are delicious. So this will help us remember, if we have a polyatomic ion that ends with ite, in its acid form it becomes ous acid. So here we have H+NO2-. NO2- is our nitrite ion. When it combines with H+, we get HNO2, which is our oxyacid form. The -ite ending changes to ous acid. So nitrite becomes nitrous acid. So again, unless you know your polyatomic ions, it gets pretty tricky in terms of naming the oxyacid. Now that we've seen the rules for this, let's continue on with some questions and test what we've learned.

Naming Acids Example 2

In this example question it says write the formula for each of the following compounds. Alright. So for a we have H₂CO₃. Alright. So think about what is making up this oxyacid. Well, we know that this is H⁺, and we know here this CO₃ is altogether, CO₃. The 2 that comes here originated from the CO₃ because here, this is carbonate ion. Remember, the ending is ate. Remember, I ate an acid and it was icky. So that means that ate will become ic acid. So that means that this represents carbonic acid. So H₂CO₃ is carbonic acid. Next, H₃PO₃. What makes it up? We know we have H⁺ here and we know that PO₃ here, a polyatomic ion, was 3 minus. We also know based on what we've seen in the polyatomic ion videos, that this would be called phosphite, phosphite, ending ends with ite. So, remember, if it ends with ite, we're gonna say here that I bite into things that are delicious. Right? So, it becomes ose acid. Also, remember that phosphorus, we use more than just the base base name. We also include or, and then it would be ose acid. So this is phosphorous acid. Finally, we have H₂SO₄, which is composed of H⁺ and SO₄, which is a polyatomic ion that is two minus. It's one of our common types of tetraoxides. Alright. So this is called sulfate. It ends with ate, so that means that our acid form would be ic acid. Just like phosphorus, sulfur uses more than just the base name. So we actually use the whole name sulfur, and remember, it becomes ic acid. So this is sulfuric acid as the name for our oxyacid. So, again, you have to remember your polyatomic ions because they go hand in hand with learning and recognizing the oxyacid forms that exist. Now that we've done this example, let's continue onward with more practice on naming oxyacids.

Write the formula for the following compound:Hypobromous acid  

• A. HBrO
• B. H₂BrO
• C. HBrO₂
• D. HBrO₃
• E. H₂BrO₄

Write the formula for the following compound:Cyanic acid

• A. HCNO
• B. HOCN
• C. H₂OCN
• D. HO₂CN
• E. HCN

Here’s what students ask on this topic:

What is the difference between binary acids and oxyacids?

Binary acids and oxyacids are two main types of acids. Binary acids consist of hydrogen and a nonmetal anion without oxygen. Examples include HCl (hydrochloric acid) and HI (hydroiodic acid). They are named using the prefix 'hydro-' followed by the base name of the nonmetal and the suffix '-ic acid'. Oxyacids, on the other hand, contain hydrogen and a polyatomic ion with oxygen. Examples include HNO₃ (nitric acid) and H₂SO₄ (sulfuric acid). The naming convention for oxyacids involves changing the suffix of the polyatomic ion from '-ate' to '-ic acid' and from '-ite' to '-ous acid'.

How do you name binary acids?

Naming binary acids involves a few simple steps. First, use the prefix 'hydro-' to indicate the presence of hydrogen. Next, take the base name of the nonmetal element involved. For most nonmetals, this is simply the element's name without any changes. However, for sulfur and phosphorus, you use the full name 'sulfur' and 'phosphor'. Finally, add the suffix '-ic acid' to complete the name. For example, HCl becomes hydrochloric acid, and H₂S becomes hydrosulfuric acid.

What are the rules for naming oxyacids?

Naming oxyacids depends on the suffix of the polyatomic ion. If the polyatomic ion ends in '-ate', change the ending to '-ic acid'. For example, NO₃^- (nitrate) becomes HNO₃ (nitric acid). If the polyatomic ion ends in '-ite', change the ending to '-ous acid'. For instance, NO₂^- (nitrite) becomes HNO₂ (nitrous acid). Remembering these rules will help you correctly name any oxyacid.

Why is acetic acid an exception to the usual acid naming rules?

Acetic acid (CH₃COOH) is an exception to the usual acid naming rules because it does not start with a hydrogen ion (H⁺) in its molecular formula. Instead, the hydrogen ion is written at the end. Despite this, it is still considered an acid because it can donate a hydrogen ion in solution. This exception highlights the importance of understanding the structure and behavior of acids beyond just their naming conventions.

What is the significance of the hydronium ion in acids?

The hydronium ion (H₃O⁺) is significant in acids because it represents the form in which hydrogen ions (H⁺) exist in aqueous solutions. When an acid dissolves in water, it donates a hydrogen ion, which combines with a water molecule to form the hydronium ion. This ion is crucial in defining the acidic properties of a solution, including its pH level and reactivity.