To determine how many compounds are more acidic than phenol from the given list, we will analyze each compound based on their acidity relative to phenol.
### Step-by-Step Solution:
1. **Identify the Acidity of Phenol**:
- Phenol (C6H5OH) can release a proton (H+) to form the phenoxide ion (C6H5O-), which is resonance stabilized. This gives phenol a moderate level of acidity.
2. **Analyze Formic Acid (HCOOH)**:
- Formic acid can dissociate to form the formate ion (HCOO-). The formate ion is resonance stabilized, making formic acid more acidic than phenol.
3. **Analyze Benzoic Acid (C6H5COOH)**:
- Benzoic acid can dissociate to form the benzoate ion (C6H5COO-), which is also resonance stabilized. Thus, benzoic acid is more acidic than phenol.
4. **Analyze Picric Acid (C6H2(NO2)3OH)**:
- Picric acid has three nitro groups that are strong electron-withdrawing groups, significantly increasing its acidity. Therefore, picric acid is more acidic than phenol.
5. **Analyze Ethanol (C2H5OH)**:
- Ethanol can dissociate to form the ethoxide ion (C2H5O-), but it is less acidic than phenol due to the +I effect of the ethyl group. Thus, ethanol is less acidic than phenol.
6. **Analyze Water (H2O)**:
- Water can dissociate to form the hydroxide ion (OH-), but it is less acidic than phenol. Therefore, water is less acidic than phenol.
7. **Analyze Ortho-Nitrophenol (C6H4(NO2)OH)**:
- Ortho-nitrophenol has a nitro group in the ortho position, which increases its acidity due to the -M effect of the nitro group. Thus, ortho-nitrophenol is more acidic than phenol.
8. **Analyze Ortho-Cresol (C6H4(CH3)OH)**:
- Ortho-cresol has a methyl group that exhibits a +I effect, making it less acidic than phenol. Therefore, ortho-cresol is less acidic than phenol.
9. **Analyze Para-Nitrophenol (C6H4(NO2)OH)**:
- Para-nitrophenol has a nitro group in the para position, which also increases its acidity due to the -M effect. Thus, para-nitrophenol is more acidic than phenol.
10. **Analyze Para-Cresol (C6H4(CH3)OH)**:
- Para-cresol, like ortho-cresol, has a methyl group that exhibits a +I effect, making it less acidic than phenol. Therefore, para-cresol is less acidic than phenol.
### Summary of Acidity Comparison:
- More acidic than phenol:
- Formic acid
- Benzoic acid
- Picric acid
- Ortho-nitrophenol
- Para-nitrophenol
- Less acidic than phenol:
- Ethanol
- Water
- Ortho-cresol
- Para-cresol
### Conclusion:
Out of the given compounds, **5 compounds are more acidic than phenol**.
