Problem 47
Question
The basicity of phosphorous acid \(\left(\mathrm{H}_{3} \mathrm{PO}_{3}\right)\) is \(\ldots \ldots \ldots \ldots . . .\) [1990-1 Mark]
Step-by-Step Solution
Verified Answer
The basicity of phosphorous acid is 2.
1Step 1: Understand Basicity
Basicity refers to the number of hydrogen atoms in an acid that can be replaced by a metal in a reaction. It is essentially counting the acidic hydrogen atoms that are capable of being ionized in water.
2Step 2: Analyze the Structure of Phosphorous Acid
The chemical formula for phosphorous acid is \(H_{3}PO_{3}\). Structurally, it can be represented as HO-P(OH)-OH, where only two of the hydrogen atoms are bound to oxygen and can be ionized (replaced by a metal) in solution.
3Step 3: Identify Ionizable Hydrogen Atoms
In the structure of phosphorous acid \(H_{3}PO_{3}\), only the two hydrogen atoms attached to the oxygen are ionizable, while the hydrogen directly bonded to phosphorus (P-H bond) is not an ionizable hydrogen.
4Step 4: Determine Basicity
Since only the two hydrogens bonded to oxygen are ionizable, the basicity of phosphorous acid is determined by these two replaceable hydrogen atoms. Thus, the basicity of \(H_{3}PO_{3}\) is 2.
Key Concepts
Ionizable Hydrogen AtomsChemical Structure AnalysisPhosphorous Acid Properties
Ionizable Hydrogen Atoms
In chemistry, understanding which hydrogen atoms in a molecule are ionizable is crucial to determining an acid's basicity. Ionizable hydrogen atoms are those that can be released as hydrogen ions (H⁺) when the acid dissolves in water. Not all hydrogen atoms are easily ionizable. So, the focus is primarily on those that are most acidic, which generally occur when hydrogen is connected to electronegative elements like oxygen or sulfur. The ionization capability depends on the bond strength and the environment of the hydrogen atom.
For phosphorous acid (H₃PO₃), it contains three hydrogen atoms in its formula. However, only the ones bonded to oxygen can ionize in aqueous solution. Specifically, only two hydrogens are bound this way, making them acidic enough to dissociate in a solution. These ionizable hydrogens contribute to the basicity of the acid.
To sum it up, the ionizable hydrogen atoms are the key players when describing an acid's strength and behavior in a chemical reaction.
For phosphorous acid (H₃PO₃), it contains three hydrogen atoms in its formula. However, only the ones bonded to oxygen can ionize in aqueous solution. Specifically, only two hydrogens are bound this way, making them acidic enough to dissociate in a solution. These ionizable hydrogens contribute to the basicity of the acid.
To sum it up, the ionizable hydrogen atoms are the key players when describing an acid's strength and behavior in a chemical reaction.
Chemical Structure Analysis
Analyzing the structure of a molecule helps explain its chemical behavior and properties. When you break down the chemical structure of phosphorous acid, it is represented as HO-P(OH)-OH. This structure indicates how the atoms are arranged and bonded together.
This representation shows that phosphorous acid contains one phosphorus atom and three oxygen atoms, with two of these oxygens being part of hydroxyl groups (OH). These hydroxyl groups are crucial because the hydrogen atoms they contain can be ionized, making them the source of the acid's basicity.
Another interesting point is that the third hydrogen atom, which is attached directly to phosphorus, does not ionize. This hydrogen forms a P-H bond rather than being part of a hydroxyl group, and as a result, it doesn’t contribute to the acidity. Thus, by analyzing the structure, the specific bonding arrangements highlight why only two hydrogen atoms are ionizable. This structural insight is important to understand the chemical behavior of phosphorous acid.
This representation shows that phosphorous acid contains one phosphorus atom and three oxygen atoms, with two of these oxygens being part of hydroxyl groups (OH). These hydroxyl groups are crucial because the hydrogen atoms they contain can be ionized, making them the source of the acid's basicity.
Another interesting point is that the third hydrogen atom, which is attached directly to phosphorus, does not ionize. This hydrogen forms a P-H bond rather than being part of a hydroxyl group, and as a result, it doesn’t contribute to the acidity. Thus, by analyzing the structure, the specific bonding arrangements highlight why only two hydrogen atoms are ionizable. This structural insight is important to understand the chemical behavior of phosphorous acid.
Phosphorous Acid Properties
Phosphorous acid,
H₃PO₃, has unique chemical properties that make it interesting. It's a diprotic acid, meaning it can donate two protons (H⁺ ions) in a reaction. The basicity, therefore, is 2, as it only has two ionizable hydrogen atoms.
Being a moderate acid, phosphorous acid presents certain characteristics in its reactions. For instance, the presence of its non-ionizable P-H bond adds distinct features not commonly seen in other oxyacids. This bond affects both the reactivity and stability of H₃PO₃.
Some important properties include:
Being a moderate acid, phosphorous acid presents certain characteristics in its reactions. For instance, the presence of its non-ionizable P-H bond adds distinct features not commonly seen in other oxyacids. This bond affects both the reactivity and stability of H₃PO₃.
Some important properties include:
- Acts as an reducing agent in some chemical reactions
- Allows selective reactions, owing to its unique structural features
- Soluble in water, making it useful in aqueous reactions
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