Phosphorus pentaoxide reacts with H2O to form an acid. What is the basicity of that acid?

Explanation

To determine the basicity of the acid formed when phosphorus pentoxide (P2O5) reacts with water (H2O), we can follow these steps:

### Step 1: Identify the Reaction
Phosphorus pentoxide reacts with water to form an acid. The chemical reaction can be written as:
\[ \text{P}_2\text{O}_5 + \text{H}_2\text{O} \rightarrow \text{H}_3\text{PO}_4 \]

### Step 2: Write the Balanced Equation
To balance the reaction, we need to ensure that the number of atoms of each element on the reactant side is equal to that on the product side. The balanced equation is:
\[ \text{P}_2\text{O}_5 + 3 \text{H}_2\text{O} \rightarrow 2 \text{H}_3\text{PO}_4 \]

### Step 3: Identify the Acid Formed
From the balanced equation, we see that phosphorus pentoxide reacts with water to form phosphoric acid (H3PO4).

### Step 4: Determine the Basicity of Phosphoric Acid
Basicity refers to the number of replaceable hydrogen ions (H⁺) in one molecule of the acid. For phosphoric acid (H3PO4):
- It has three hydrogen atoms that can dissociate as H⁺ ions when dissolved in water.

### Step 5: Conclusion
Thus, the basicity of phosphoric acid (H3PO4) is 3, as it can release three hydrogen ions.

### Final Answer
The basicity of the acid formed (phosphoric acid) is 3.

---