Naming Acids: Videos & Practice Problems

Acids are covalent compounds that typically begin with a hydrogen ion (H⁺), also known as a hydronium ion. These compounds are composed only of nonmetals. An example of an exception to this rule is acetic acid, which can be written with the hydrogen ion at the end, as in:

CH₃COOH Binary acids are a subset of acids that bond hydrogen ions to nonmetal anions, excluding oxygen. To name binary acids, the prefix 'hydro-' is used, followed by the base name of the nonmetal and ending with 'ic acid.' For example,

HCl becomes hydrochloric acid.

Oxy acids, on the other hand, are covalent compounds that contain hydrogen ions bonded to a polyatomic ion with oxygen. The naming of oxy acids is based on the ending of the polyatomic ion: if it ends in '-ate,' the acid name ends in '-ic acid' (e.g., nitrate to nitric acid), and if it ends in '-ite,' it changes to '-ous acid' (e.g., nitrite to nitrous acid). Understanding the structure and naming conventions of acids is crucial for recognizing and categorizing different types of chemical compounds.

Acids and Their Structure

Acids are typically defined as covalent compounds that begin with a hydrogen ion (H⁺), which is also known as a hydronium ion. A covalent compound consists solely of nonmetals bonded together. Understanding the periodic table and the classification of elements is essential for identifying nonmetals.

Common examples of acids include hydrochloric acid (HCl), nitrous acid (HNO₂), and sulfuric acid (H₂SO₄). These acids are characterized by their covalent nature and the presence of hydrogen, which signifies their classification as acids. While many acids follow the rule of starting with a hydrogen ion, exceptions exist. A notable example is acetic acid, which can be represented as CH₃COOH. In this structure, the hydrogen ion appears at the end, demonstrating that not all acids strictly adhere to the initial hydrogen placement.

With a foundational understanding of acids established, the next step involves exploring the various types of acids and the conventions for naming them. This knowledge will enhance comprehension of acid properties and their applications in chemistry.

Binary Acids

Binary acids are a specific type of covalent compound that contain hydrogen ions (H⁺) bonded to a nonmetal anion, which does not include oxygen. These acids typically begin with hydrogen and are characterized by their formation from a nonmetal with a negative charge. For example, when considering iodine, which has a charge of -1, the combination with hydrogen (which has a charge of +1) results in the binary acid HI.

To name binary acids, follow a systematic approach. First, use the prefix "hydro-" to indicate the presence of the H⁺ ion. Next, take the base name of the nonmetal. This base name remains unchanged for most nonmetals, but there are exceptions for sulfur and phosphorus. In the case of sulfur, the entire name "sulfur" is used, while for phosphorus, the name is modified to "phosphor" plus "or" to form "phosphoric." Finally, conclude the name with "ic acid." Thus, the naming convention for binary acids can be summarized as follows: "hydro-" + base name of the nonmetal + "ic acid."

By applying these rules, one can accurately name any binary acid, ensuring a clear understanding of their composition and structure.

Naming Binary Acids Example

When writing the formulas for binary acids, such as hydroiodic acid, hydroselenic acid, and hydrofluoric acid, it is essential to understand the role of the hydrogen ion (H⁺) and the nonmetals involved. Each of these acids contains H⁺ and ends with the suffix "-ic acid," indicating they are binary acids.

The base name of each acid reveals the nonmetal component. For hydroiodic acid, the base name "iod" refers to iodine, which is in Group 7A and has a charge of -1. Therefore, the formula for hydroiodic acid is H₁I₁, which simplifies to HI, as the charges cancel out.

In the case of hydrofluoric acid, "fluor" indicates fluorine, also in Group 7A with a -1 charge. Thus, hydrofluoric acid is represented as H₁F₁, simplifying to HF.

For hydroselenic acid, the base name "selen" refers to selenium, which is in Group 6A and has a charge of -2. Here, the charges differ, so we apply the crisscross method: the +1 charge from hydrogen and the -2 charge from selenium result in H₂Se. Therefore, the formula for hydroselenic acid is H₂Se.

In summary, when determining the formulas for binary acids, remember to identify the nonmetal, assess the charges, and apply the cancellation or crisscross method as needed. This approach is consistent with the principles of writing ionic compounds, where understanding the charges of ions is crucial for accurate formula representation.

Give the systematic name for the following compound:H₂S

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

Answer: (B)

Give the systematic name for the following compound:HCN

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

Answer: (E)

Oxyacids Formation

Oxyacids are a specific type of acid characterized by their composition of hydrogen ions bonded to polyatomic ions that contain oxygen. This classification highlights the presence of oxygen, as indicated by the prefix "oxy." Oxyacids are covalent compounds, meaning they are formed from nonmetals.

To understand how to form an oxyacid, consider the hydrogen ion (H⁺) and a polyatomic ion that includes oxygen, such as the nitrate ion (NO₃^-). When combining these ions, the charges can cancel out if they are equal. For example, the combination of H⁺ and NO₃^- results in the formula HNO₃, which is the chemical representation of nitric acid, an oxyacid.

In summary, oxyacids are formed by the combination of hydrogen ions with polyatomic ions containing oxygen, resulting in covalent compounds that play a significant role in various chemical reactions and processes.

Rules for Naming Oxyacids

Understanding the naming of oxyacids is essential, and it begins with a solid grasp of polyatomic ions. When naming oxyacids, there are specific rules to follow based on the endings of these ions.

The first rule states that if a polyatomic ion ends with -ate, the corresponding acid will end with -ic acid. A helpful mnemonic to remember this is "I ate something icky," which reinforces that -ate transforms to -ic in acid form. For example, the nitrate ion (NO₃^-) combines with hydrogen (H⁺) to form nitric acid (HNO₃).

Conversely, if a polyatomic ion ends with -ite, the acid will end with -ous acid. A useful phrase to remember this is "I only bite into delicious things," indicating that -ite changes to -ous in acid form. For instance, the nitrite ion (NO₂^-) combines with hydrogen to yield nitrous acid (HNO₂).

These naming conventions are crucial for accurately identifying and communicating about oxyacids. Mastery of polyatomic ions is a prerequisite for successfully applying these rules, as they form the foundation for understanding the structure and nomenclature of oxyacids.

Naming Oxyacid Example

When writing the formulas for oxyacids, it's essential to understand the relationship between the polyatomic ions and their corresponding acids. For instance, the formula H₂CO₃ represents carbonic acid. This compound consists of two hydrogen ions (H⁺) and the carbonate ion (CO₃^2-). The naming convention follows that when the polyatomic ion ends in "-ate," the acid name will end in "-ic." Thus, CO₃^2- becomes carbonic acid.

Next, consider the formula H₃PO₃, which corresponds to phosphorous acid. This compound is made up of three hydrogen ions (H⁺) and the phosphite ion (PO₃^3-). The "-ite" ending of the phosphite ion indicates that the acid name will end in "-ous." Therefore, the full name is phosphorous acid.

Lastly, the formula H₂SO₄ represents sulfuric acid. This acid consists of two hydrogen ions (H⁺) and the sulfate ion (SO₄^2-). Similar to the previous examples, the "-ate" ending of the sulfate ion leads to the acid being named sulfuric acid.

In summary, recognizing the polyatomic ions and their naming conventions is crucial for accurately determining the names of oxyacids. The general rules are:

• If the polyatomic ion ends in "-ate," the acid name will end in "-ic."
• If the polyatomic ion ends in "-ite," the acid name will end in "-ous."

Understanding these relationships will aid in mastering the naming of oxyacids and their corresponding formulas.

Write the formula for the following compound:Hypobromous acid  

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

Answer: (A)

Write the formula for the following compound:Cyanic acid

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

Answer: (B)

Here’s what students ask on this topic:

What are the rules for naming acids?

In chemistry, acids are named based on the presence or absence of oxygen in the molecule. Here are the general rules for naming acids:

1. Binary Acids: These are acids that consist of hydrogen and one other nonmetal element. When naming a binary acid, you start with the prefix "hydro-", then add the stem of the nonmetal element's name, and finally add the suffix "-ic" followed by the word "acid". For example, HCl (hydrogen chloride) is named hydrochloric acid.
2. Oxyacids: These acids contain hydrogen, oxygen, and another element (the central atom). The naming depends on the polyatomic ion (the ion with multiple atoms) that the acid is derived from:

• If the polyatomic ion ends in "-ate", change the ending to "-ic" and add "acid". For example, HNO 3 (nitric acid) is derived from the nitrate ion NO 3 - .
• If the polyatomic ion ends in "-ite", change the ending to "-ous" and add "acid". For example, HNO 2 (nitrous acid) is derived from the nitrite ion NO 2 - .

Remember, you don't use the "hydro-" prefix for oxyacids, and the "ic" or "ous" suffix.

Which rule should be followed when naming binary acids?

When naming binary acids, which are acids that consist of hydrogen and one other nonmetallic element, there is a specific nomenclature rule to follow:

1. Start with the prefix "hydro-".
2. Add the root of the name of the nonmetal element.
3. End with the suffix "-ic".
4. Follow with the word "acid".

For example, if you have an acid with hydrogen and chlorine, you would name it hydrochloric acid. Here, "hydro-" indicates the presence of hydrogen, "chlor-" is the root for chlorine, and "-ic" is the suffix used for binary acids. Finally, the term "acid" is added to indicate that the compound is indeed an acid. So, H 2 S in aqueous solution is called hydrochloric acid, while H 2 S would be named hydrosulfuric acid. Remember, this rule is only for binary acids in their aqueous form; the naming convention changes for molecular compounds and oxyacids.