What is the basicity of `H_(3)PO_(3)` ?

Answer

To determine the basicity of \( H_3PO_3 \) (phosphorous acid), we will follow these steps:

### Step 1: Understand Basicity
Basicity refers to the number of hydrogen ions (\( H^+ \)) that an acid can donate when dissolved in water.

### Step 2: Identify the Structure of \( H_3PO_3 \)
Phosphorous acid has the following structure:
- It consists of one phosphorus atom (P) at the center.
- There are three hydrogen atoms (H) attached to the phosphorus.
- Two of these hydrogen atoms are connected to oxygen atoms (forming hydroxyl groups, \( -OH \)), and one hydrogen is directly bonded to phosphorus.

### Step 3: Count Ionizable Hydrogens
In \( H_3PO_3 \):
- The two hydrogen atoms connected to the oxygen atoms (in the \( -OH \) groups) are ionizable.
- The hydrogen atom directly bonded to phosphorus is not ionizable because it does not have the ability to dissociate as \( H^+ \).

### Step 4: Determine Basicity
Since there are two ionizable hydrogen atoms in \( H_3PO_3 \), the basicity of this acid is 2. This means \( H_3PO_3 \) can donate two protons (\( H^+ \)) when it dissociates in solution.

### Conclusion
Thus, the basicity of \( H_3PO_3 \) is 2, indicating that it is a diprotic acid.

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