Binary Acids: Videos & Practice Problems

Binary acids are covalent compounds consisting of hydrogen ions (H⁺) bonded to nonmetal anions, excluding those with oxygen. They include acids like hydrobromic acid (HBr) and hydrosulfuric acid (H₂S). The strength of binary acids is determined by their ability to dissociate in water. Strong binary acids, such as hydroiodic (HI), hydrobromic (HBr), and hydrochloric (HCl) acids, dissociate completely, making them strong electrolytes that donate protons readily. However, hydrofluoric acid (HF) is a weak binary acid, partially dissociating and favoring its molecular form, thus behaving as a weak electrolyte.

The strength of binary acids can be compared using electronegativity and atomic radius. For elements in the same period, the greater the electronegativity, the stronger the acid. Conversely, for elements in the same group, a larger atomic radius correlates with stronger acidity. These trends help predict the relative strengths of binary acids based on their position on the periodic table and the properties of the non-hydrogen element they are bonded to.

Binary Acids

Binary acids are a specific category of covalent compounds that consist of a hydrogen ion (H⁺) bonded to a nonmetal anion, excluding any oxygen atoms. This means that binary acids do not contain oxygen in their structure. A couple of common examples illustrate this concept effectively.

For instance, when H⁺ bonds with Br^-, the charges are equal and cancel each other out, resulting in the compound HBr, known as hydrobromic acid. Similarly, when H⁺ connects with S^2-, the charges also balance, leading to the formation of H₂S, which is referred to as hydrosulfuric acid. These examples highlight the defining characteristic of binary acids: the absence of oxygen in their molecular structure.

Binary Acid Identification Example

A binary acid is defined as an acid that consists of only two elements, typically hydrogen and a nonmetal, and does not contain oxygen. To identify a binary acid, one must look for a covalent compound that begins with hydrogen and lacks oxygen in its structure.

For example, hydrofluoric acid (HF) is a classic binary acid. It is covalent, starts with hydrogen, and contains no oxygen, making it a valid representation of a binary acid. In contrast, compounds like barium chloride do not qualify as acids since they do not release H⁺ ions. Similarly, lithium hydride (LiH) is an ionic compound formed from a metal cation (Li⁺) and a basic anion (H^-), categorizing it as a base rather than an acid.

Thus, among the options provided, the only valid binary acid is hydrofluoric acid (HF), as it meets all the criteria for this classification.

Binary Acid Strengths

Understanding the strengths of binary acids is crucial in chemistry, particularly when discussing their behavior in aqueous solutions. Binary acids consist of hydrogen and a nonmetal, typically a halogen from Group 7A of the periodic table, which includes fluorine, chlorine, bromine, and iodine. Among these, only certain halo acids are classified as strong binary acids, specifically hydroiodic acid (HI), hydrobromic acid (HBr), and hydrochloric acid (HCl). Notably, hydrofluoric acid (HF) is considered a weak binary acid, which we will explore further.

Strong acids, such as HCl, are characterized as strong electrolytes because they completely dissociate or ionize in water, releasing H⁺ ions readily. This complete ionization means that strong acids favor the product side of the reaction, transforming entirely into ions. For example, the dissociation of hydrochloric acid can be represented as:

HCl (aq) → H⁺ (aq) + Cl^- (aq)

This reaction illustrates that all HCl molecules break down into H⁺ and Cl^- ions, demonstrating the strong acid's ability to donate protons easily.

In contrast, weak acids, such as hydrocyanic acid (HCN), only partially dissociate in solution. The dissociation of HCN can be represented with a double arrow to indicate the equilibrium between reactants and products:

HCN (aq) ↔ H⁺ (aq) + CN^- (aq)

In this case, the larger arrow pointing to the left signifies that the reactant side (HCN) is favored, meaning that a greater concentration of HCN remains intact compared to the ions produced. The smaller arrow pointing to the right indicates that only a small amount of H⁺ and CN^- ions are formed, reflecting the weak acid's reluctance to donate protons.

In summary, the distinction between strong and weak binary acids lies in their ability to ionize in water. Strong acids like HCl dissociate completely, while weak acids like HCN only partially dissociate, favoring the reactants. This fundamental understanding of acid strength is essential for predicting the behavior of acids in various chemical reactions.

Binary Acid Strength Example

In aqueous solutions, acids can be classified based on their ability to ionize, which is crucial for understanding their strength. The general formula for an acid can be represented as HA, where it dissociates into H⁺ ions and A^- ions. A strong acid completely ionizes in solution, meaning it produces 100% of H⁺ and A^- ions, leaving no undissociated acid molecules. In contrast, weak acids only partially ionize, resulting in a mixture of dissociated ions and undissociated acid.

To identify the strong, weak, and weakest acids among given options, one must analyze the number of H⁺ and A^- ions produced relative to the undissociated acid (HA). For instance, if one solution shows complete dissociation with no remaining HA, it is classified as a strong acid. In the example provided, the middle solution demonstrates this characteristic, confirming it as the strong acid.

Next, to differentiate between weak and weakest acids, we examine the extent of dissociation. If one solution has a higher concentration of undissociated acid compared to the ions produced, it indicates a weaker acid. For example, if one solution has 9 HA molecules with only 1 H⁺ and 1 A^-, it shows minimal dissociation, making it the weakest acid. Conversely, a solution with fewer undissociated acid molecules and more ions would be classified as a weak acid.

In summary, the strength of an acid is determined by its degree of ionization: strong acids fully dissociate, weak acids partially dissociate, and the weakest acids dissociate the least. Understanding this concept is essential for predicting the behavior of acids in chemical reactions and their applications in various fields.

Comparing Binary Acid Strength

Binary acids, such as HI, HBr, and HCl, exhibit varying strengths that can be compared based on specific periodic trends. The strength of these acids is influenced by the electronegativity and atomic radius of the non-hydrogen element involved. Understanding these trends is essential for determining acid strength.

Electronegativity, denoted as en, increases as you move from left to right across a period in the periodic table. Conversely, atomic radius, abbreviated as ar, increases as you move down a group. These trends are crucial when comparing binary acids.

When comparing binary acids from the same period, the acid strength is determined by the electronegativity of the non-hydrogen element. Specifically, a higher electronegativity correlates with a stronger acid. For example, among halogen acids, HF is weaker than HCl, HBr, and HI due to the lower electronegativity of fluorine compared to chlorine, bromine, and iodine.

In contrast, when comparing acids from the same group, the atomic radius becomes the determining factor. A larger atomic radius typically results in a stronger acid. For instance, HI is a stronger acid than HBr and HCl because iodine has a larger atomic radius than bromine and chlorine, allowing for easier dissociation of the hydrogen ion.

In summary, the strength of binary acids can be effectively compared using periodic trends: electronegativity for elements in the same period and atomic radius for elements in the same group. This understanding is vital for predicting and rationalizing the behavior of various binary acids.

Comparing Binary Acid Strength Example

When comparing the strengths of binary acids such as HF (hydrofluoric acid), HCl (hydrochloric acid), HBr (hydrobromic acid), and HI (hydroiodic acid), it is essential to consider the non-hydrogen element in each acid. The strength of these acids can be analyzed through the atomic radius of the halogens: fluorine, chlorine, bromine, and iodine.

As you move down the group in the periodic table, the atomic radius increases. This increase in atomic size correlates with acid strength; larger atoms can stabilize the negative charge of the conjugate base more effectively. Therefore, HI, which contains iodine, has the largest atomic radius and is the strongest acid among the group.

Conversely, HF, which contains fluorine, has the smallest atomic radius. This smaller size results in a stronger bond between hydrogen and fluorine, making it less willing to dissociate and thus rendering HF the weakest acid in this comparison. Therefore, the correct answer is that HF is the weakest acid.

Comparing Binary Acid Strength Example

When comparing the strengths of binary acids that are not located within the same period or group on the periodic table, specific guidelines can be applied. If the binary acids are separated by one period, the comparison should be based on electronegativity. Conversely, if they are separated by more than one period, atomic radius becomes the determining factor for acid strength.

For example, consider the binary acids H₂Se, HF, H₂Te, and H₂S. To identify the weakest acid, we first examine the non-hydrogen elements: selenium, fluorine, tellurium, and sulfur. Since sulfur, selenium, and tellurium are in the same group, we can utilize atomic radius for comparison. A larger atomic radius typically indicates a stronger binary acid. Therefore, H₂Te is stronger than H₂Se, and H₂Se is stronger than H₂S, eliminating H₂Te and H₂Se as candidates for the weakest acid.

Next, we compare HF and H₂S. Since these two acids are separated by one period, we apply electronegativity for our analysis. Fluorine, located in the second period, is more electronegative than sulfur, which is in the third period. Given that fluorine is the most electronegative element, HF is determined to be more acidic than H₂S.

Through this process of elimination, we conclude that H₂S is the weakest acid among the options provided.

Which of the following acids would be classified as the strongest? 
a) CH₄             b) H₂Te            c) H₂S             d) PH₃             e) BH₃

• A. CH₄
• B. H₂Te
• C. H₂S
• D. PH₃
• E. BH₃

Answer: (B)

Here’s what students ask on this topic:

Which substance is a binary acid?

A binary acid is a compound that contains only two different elements: hydrogen and one other nonmetal. The general formula for a binary acid is HX, where H stands for hydrogen and X represents the nonmetal. An example of a binary acid is hydrochloric acid (HCl), where hydrogen is combined with chlorine. Other examples include hydrobromic acid (HBr), hydroiodic acid (HI), and hydrofluoric acid (HF). These acids are called "binary" because they consist of two elements. When dissolved in water, binary acids release hydrogen ions (H⁺), which are responsible for the acidic properties of the solution.

What is a binary acid?

A binary acid is a chemical compound that contains only two different elements: hydrogen and one other nonmetal element. The general formula for a binary acid is HX, where H stands for hydrogen and X represents the nonmetal element. When dissolved in water, binary acids release hydrogen ions (H⁺), which is what makes them acidic. The strength of a binary acid depends on the ease with which it can donate a hydrogen ion. This is influenced by the bond strength between the hydrogen and the nonmetal atom; weaker bonds usually mean stronger acids. Common examples of binary acids include hydrochloric acid (HCl), hydrobromic acid (HBr), and hydroiodic acid (HI). These acids are widely used in various industries and in laboratory settings for different applications, such as pH adjustment, cleaning, and as reagents in chemical reactions.

Which of these is not a binary acid?

A binary acid is a compound that contains hydrogen and one other nonmetal element, typically forming an acid when dissolved in water. Binary acids have the general formula HX, where X is the nonmetal element. To determine which of these is not a binary acid, you would look for a compound that does not fit this description.

For example, hydrochloric acid (HCl), hydrobromic acid (HBr), and hydroiodic acid (HI) are all binary acids because they consist of hydrogen and a halogen. However, if you encounter a compound like sulfuric acid (H₂SO₄), it is not a binary acid because it contains hydrogen, sulfur, and oxygen. Sulfuric acid is instead classified as an oxyacid because it includes oxygen in addition to hydrogen and another nonmetal (sulfur in this case).

So, if you're given a list of compounds, the one that includes oxygen or more than two elements is not a binary acid.