How many of these days acids are mobobasic in nature?
`H_(2)S, H_(2)O_(2), H_(3)O_(2), HCOOH,H_(3)BO_(3),H_(3)PO_(2), HXO_(4), Ph-SO_(3)H`

Answer

To determine how many of the given acids are monobasic in nature, we need to analyze each acid based on its structure and the number of replaceable hydrogen ions (H⁺) it can donate. An acid is considered monobasic if it can donate only one H⁺ ion.

Let's analyze each acid step by step:

1. **H₂S (Hydrogen Sulfide)**:
- Structure: H₂S can dissociate to give H⁺ and HS⁻.
- Replaceable H⁺: 2 (both H⁺ can be released).
- Basicity: 2 (dibasic).

2. **H₂O₂ (Hydrogen Peroxide)**:
- Structure: H₂O₂ does not behave as a typical acid; it does not donate H⁺ easily.
- Replaceable H⁺: 0.
- Basicity: 0 (not acidic).

3. **H₃O₂ (Dihydroxydihydronium)**:
- Structure: H₃O₂ can donate H⁺ from the hydroxyl groups.
- Replaceable H⁺: 2.
- Basicity: 2 (dibasic).

4. **HCOOH (Formic Acid)**:
- Structure: HCOOH can dissociate to give H⁺ and HCOO⁻.
- Replaceable H⁺: 1 (the H from the carboxyl group).
- Basicity: 1 (monobasic).

5. **H₃BO₃ (Boric Acid)**:
- Structure: H₃BO₃ can accept hydroxide ions but can only donate 1 H⁺.
- Replaceable H⁺: 1.
- Basicity: 1 (monobasic).

6. **H₃PO₂ (Phosphorous Acid)**:
- Structure: H₃PO₂ can dissociate to give H⁺ and H₂PO₂⁻.
- Replaceable H⁺: 1 (the H from the hydroxyl group).
- Basicity: 1 (monobasic).

7. **HXO₄ (Generalized Acid)**:
- Structure: Similar to other oxoacids, it can donate one H⁺ from the hydroxyl group.
- Replaceable H⁺: 1.
- Basicity: 1 (monobasic).

8. **Ph-SO₃H (Benzene Sulfonic Acid)**:
- Structure: The sulfonic acid group can donate one H⁺.
- Replaceable H⁺: 1.
- Basicity: 1 (monobasic).

Now, let's summarize the findings:

- H₂S: Dibasic (2)
- H₂O₂: Not acidic (0)
- H₃O₂: Dibasic (2)
- HCOOH: Monobasic (1)
- H₃BO₃: Monobasic (1)
- H₃PO₂: Monobasic (1)
- HXO₄: Monobasic (1)
- Ph-SO₃H: Monobasic (1)

**Total Monobasic Acids**: HCOOH, H₃BO₃, H₃PO₂, HXO₄, Ph-SO₃H = 5 acids.

### Final Answer:
There are **5** acids that are monobasic in nature.