Naming Acids: Videos & Practice Problems

Acids are covalent compounds that typically begin with a hydrogen ion (H⁺), forming hydronium ions in solution. Binary acids consist of hydrogen and a nonmetal anion, while oxyacids contain hydrogen bonded to a polyatomic ion with oxygen. Naming binary acids involves the prefix "hydro," the base name of the nonmetal, and the suffix "ic acid." For oxyacids, if the polyatomic ion ends in "ate," it changes to "ic acid," and if it ends in "ite," it changes to "ous acid." Understanding these rules is essential for proper acid nomenclature.

Naming Acids

An acid is defined as a covalent compound that typically begins with a hydrogen ion (H⁺), which is also known as a hydronium ion. Covalent compounds are formed exclusively from nonmetals bonded together. To identify nonmetals, one can refer to the periodic table and the classifications of elements within it.

Common examples of acids include HCl (hydrochloric acid), HNO₂ (nitrous acid), and H₂SO₄ (sulfuric acid). All these acids are covalent, as they consist of nonmetals and start with hydrogen, indicating their acidic nature. While many acids follow this pattern, exceptions do exist. A notable example is acetic acid, which can be represented as CH₃COOH. In this case, the hydrogen ion is positioned at the end of the formula, deviating from the typical structure of starting with hydrogen.

Understanding the basic structure of acids sets the foundation for exploring the various types of acids and the rules for naming them, which will be discussed further in subsequent lessons.

Naming 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 that carries a negative charge. For example, when hydrogen bonds with iodine (which has a charge of -1), the resulting compound is HI, known as hydroiodic acid.

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 involved. 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 "phosphoric" is derived from its base name "phospha" with the addition of "or." 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."

Understanding these principles allows for the correct identification and naming of binary acids, which are essential in various chemical contexts.

Naming Acids Example 1

In this discussion, we explore how to write the formulas for binary acids, specifically hydroiodic acid, hydroselenic acid, and hydrofluoric acid. Each of these acids contains the hydrogen ion (H⁺), which is a common feature of binary acids, indicated by the prefix "hydro" and the suffix "-ic acid."

To derive the formulas, we first identify the nonmetals involved:

• For hydroiodic acid, the base name "iod" refers to iodine, which has a charge of -1 (as it is in Group 7A).
• In hydroselenic acid, "selen" indicates selenium, which has a charge of -2 (from Group 6A).
• For hydrofluoric acid, "fluor" denotes fluorine, also with a charge of -1 (from Group 7A).

Next, we apply the rules for combining these elements based on their charges:

• For hydroiodic acid (HI), the charges are the same (H⁺ and I^-), so they simply combine to form H₁I₁ or HI.
• For hydrofluoric acid (HF), similarly, the charges are equal (H⁺ and F^-), resulting in H₁F₁ or HF.
• In the case of hydroselenic acid (H₂Se), the charges differ (H⁺ and Se^-2). Here, we crisscross the charges: one hydrogen ion combines with selenium, and two hydrogen ions are needed to balance the -2 charge of selenium, resulting in H₂Se.

These principles of charge balancing and crisscrossing are essential for writing the correct formulas for binary acids. Understanding these rules will aid in mastering the writing of ionic compounds as well.

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)

Naming Acids

Oxyacids are a specific type of acid characterized by their covalent nature, as they consist of hydrogen ions bonded to polyatomic ions that contain oxygen. The term "oxy" in oxyacid highlights the presence of oxygen in their structure. To understand how oxyacids are formed, consider the combination of a hydrogen ion (H⁺) with a polyatomic ion that includes oxygen, such as the nitrate ion (NO₃^-). When the charges of the ions are equal, they can simply cancel each other out during the formation of the compound. For example, when H⁺ combines with NO₃^-, the resulting formula is HNO₃, which is known as nitric acid. This compound is classified as an oxyacid because it is composed entirely of nonmetals, with the hydrogen ion positioned at the beginning of the molecular structure. Understanding the formation of oxyacids is essential for further exploration of their naming conventions and properties.

Naming Acids

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 the suffix -ate, the corresponding acid will end with -ic acid. A helpful mnemonic to remember this is: "I ate something icky." For example, when we take the nitrate ion, which is represented as NO₃^-, and combine it with a hydrogen ion (H⁺), we form HNO₃, known as nitric acid.

Conversely, if the 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." For instance, the nitrite ion, NO₂^-, when combined with a hydrogen ion, results in HNO₂, which is called nitrous acid.

In summary, the naming conventions for oxyacids hinge on the endings of their corresponding polyatomic ions. The transformation from -ate to -ic acid and from -ite to -ous acid is crucial for accurate chemical nomenclature. Mastering these rules will significantly enhance your ability to name and understand oxyacids effectively.

Naming Acids Example 2

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 is derived from the carbonate ion (CO₃^2-), where the suffix "-ate" in the ion indicates that the acid will end in "-ic." Thus, we can remember the phrase "I ate an acid and it was icky," which helps us recall that the carbonate ion leads to carbonic acid.

Next, consider the formula H₃PO₃. This compound consists of the hydrogen ion (H⁺) and the phosphite ion (PO₃^3-). The suffix "-ite" in the ion suggests that the corresponding acid will end in "-ous." Therefore, this compound is known as phosphorous acid, with the full name reflecting the base name of phosphorus.

Lastly, the formula H₂SO₄ corresponds to sulfuric acid. This acid is derived from the sulfate ion (SO₄^2-), which also ends in "-ate," leading to the "-ic" suffix in the acid's name. Similar to phosphorus, sulfur's full name is used in the acid's nomenclature, resulting in sulfuric acid.

Understanding these naming conventions and the connection between polyatomic ions and their acids is crucial for accurately identifying and naming oxyacids. This knowledge will aid in further practice and mastery of the topic.

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 binary acids?

Naming binary acids involves three main steps:

1. **Prefix**: Use the prefix "hydro-" to indicate the presence of hydrogen.

2. **Base Name**: Use the base name of the nonmetal element. For most nonmetals, this is the root of their name. However, for sulfur and phosphorus, use the full name (sulfur) or a modified form (phosphor-).

3. **Suffix**: Add the suffix "-ic acid" to the base name.

For example, HCl is named hydrochloric acid, and H₂S is named hydrosulfuric acid.

How do you name oxyacids?

Naming oxyacids depends on the ending of the polyatomic ion:

1. **If the polyatomic ion ends in "-ate"**: Change the ending to "-ic acid". For example, HNO₃ (nitrate) becomes nitric acid.

2. **If the polyatomic ion ends in "-ite"**: Change the ending to "-ous acid". For example, HNO₂ (nitrite) becomes nitrous acid.

Remembering these rules is crucial for correctly naming oxyacids.

What is the difference between binary acids and oxyacids?

Binary acids consist of hydrogen and a nonmetal anion, and they do not contain oxygen. Examples include HCl (hydrochloric acid) and H₂S (hydrosulfuric acid).

Oxyacids, on the other hand, contain hydrogen bonded to a polyatomic ion that includes oxygen. Examples include HNO₃ (nitric acid) and H₂SO₄ (sulfuric acid).

The naming conventions for these acids also differ, with binary acids using the "hydro-" prefix and "-ic acid" suffix, while oxyacids change the polyatomic ion endings from "-ate" to "-ic acid" and "-ite" to "-ous acid".

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

Acetic acid (CH₃COOH) is an exception because it does not follow the typical structure of acids starting with a hydrogen ion. Instead, the hydrogen ion is at the end of the formula. Despite this, it is still considered an acid because it can donate a hydrogen ion (H⁺) in solution. This exception highlights the importance of understanding the underlying chemistry rather than relying solely on naming conventions.

How do you determine the name of an acid from its chemical formula?

To determine the name of an acid from its chemical formula, follow these steps:

1. **Identify if it is a binary acid or an oxyacid**:

- **Binary acids**: Consist of hydrogen and a nonmetal. Use the prefix "hydro-", the base name of the nonmetal, and the suffix "-ic acid". For example, HCl is hydrochloric acid.

- **Oxyacids**: Contain hydrogen and a polyatomic ion with oxygen. If the polyatomic ion ends in "-ate", change it to "-ic acid". If it ends in "-ite", change it to "-ous acid". For example, H₂SO₄ (sulfate) becomes sulfuric acid, and H₂SO₃ (sulfite) becomes sulfurous acid.