Naming Acids: Videos & Practice Problems

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

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, which is a characteristic feature of acids. Some acids, like HCl, are relatively simple, while others, such as H₃PO₄ (phosphoric acid), are more complex.

It is important to note that while most acids begin with a hydrogen ion, there are exceptions. A notable example is acetic acid, which can be represented in two ways: one aligns with the definition, starting with hydrogen, while the other is written as CH₃COOH, where the hydrogen ion appears at the end. Despite this variation, acetic acid remains classified as an acid.

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

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, representing a typical binary 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, except 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."

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

Naming Acids Example 1

When writing the formulas for binary acids, it is essential to recognize that the prefix "hydro" indicates the presence of an H⁺ ion. The naming convention for these acids ends with "-ic acid," and the base name reveals the nonmetal involved. For example, in hydroiodic acid, the base name "iod" refers to iodine, which has a charge of -1 as it belongs to Group 7A of the periodic table. Similarly, hydrofluoric acid involves fluorine, also a Group 7A element with a -1 charge. In contrast, hydroselenic acid is based on selenium, which is in Group 6A and carries a -2 charge.

To derive the formulas, we apply the following principles:

1. **Hydroiodic Acid (HI)**: Since both the H⁺ and I^- ions have charges of +1 and -1 respectively, they cancel each other out, resulting in the formula H₁I₁ or simply HI.

2. **Hydrofluoric Acid (HF)**: Similar to hydroiodic acid, the charges of H⁺ and F^- are both +1 and -1, leading to the formula H₁F₁ or HF.

3. **Hydroselenic Acid (H₂Se)**: Here, the charges differ; H⁺ has a +1 charge while Se^2- has a -2 charge. To balance the charges, we crisscross the numbers: one H⁺ ion pairs with two Se^2- ions, resulting in the formula H₂Se.

Understanding these rules is crucial for accurately writing the formulas of binary acids. If you need further clarification, reviewing the principles of writing ionic compounds can provide additional insights into the process.

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 -ate, the corresponding acid will have the suffix -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 the polyatomic ion ends with -ite, the acid will take on the suffix -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).

In summary, mastering the naming of oxyacids hinges on recognizing the endings of polyatomic ions. The transformation from -ate to -ic acid and from -ite to -ous acid is crucial for accurate nomenclature in chemistry.

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 with "-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 contains the phosphite ion (PO₃^3-), which ends with "-ite." The rule here is that "-ite" ions correspond to acids that end with "-ous." Therefore, this compound is named phosphorous acid. It's also important to note that when naming acids derived from phosphorus, we include the full name, leading to the term "phosphorous acid."

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

In summary, recognizing the polyatomic ions and their naming conventions is crucial for accurately identifying and naming oxyacids. The transformation from the ion to the acid name hinges on the suffixes used in the polyatomic ions, which guide the naming process effectively.

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 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.