Conjugate acid of `HPO_(4)^(2-)`, is

Options

A. `H_(3)P_(4)`
B. `H_(2)PO_(4)^(-)`
C. `PO_(4)^(3-)`
D. `H_(3)PO_(4)`

Answer

To find the conjugate acid of \( HPO_4^{2-} \), we can follow these steps:

### Step 1: Identify the species
The species in question is \( HPO_4^{2-} \). This ion is known as hydrogen phosphate.

### Step 2: Understand the concept of conjugate acids and bases
In Brønsted-Lowry theory, a conjugate acid is formed when a base accepts a proton (H⁺). Conversely, a conjugate base is formed when an acid donates a proton.

### Step 3: Determine the action of the species
Since \( HPO_4^{2-} \) can accept a proton, it acts as a Brønsted base.

### Step 4: Add a proton to the species
When \( HPO_4^{2-} \) accepts a proton (H⁺), the reaction can be represented as:
\[ HPO_4^{2-} + H^+ \rightarrow H_2PO_4^{-} \]

### Step 5: Identify the conjugate acid
The product of this reaction, \( H_2PO_4^{-} \), is the conjugate acid of \( HPO_4^{2-} \).

### Final Answer
Thus, the conjugate acid of \( HPO_4^{2-} \) is \( H_2PO_4^{-} \).

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