Arrange pH of the given compounds in decreasing order:
(1) Phenol
(2) Ethyl alcohol
(3) Formic acid
(4). Benzoic acid

Options

A. `1 gt 2 gt 3 gt 4`
B. `2 gt 1 gt 4 gt 3`
C. ` 3 gt 2 gt 4 gt 1`
D. `4 gt 3 gt 1 gt 2`

Answer

To arrange the pH of the given compounds (Phenol, Ethyl alcohol, Formic acid, and Benzoic acid) in decreasing order, we need to analyze their acidic strengths first. The pH of a solution is inversely related to its acidic strength; that is, a stronger acid will have a lower pH.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Structures:**
- **Phenol (C6H5OH)**: A weak acid that can donate a proton (H+).
- **Ethyl Alcohol (C2H5OH)**: An alcohol that is not acidic.
- **Formic Acid (HCOOH)**: A weak acid that can donate a proton.
- **Benzoic Acid (C6H5COOH)**: A weak acid that can donate a proton.

2. **Determine the Acidic Strength:**
- **Phenol**: When phenol loses a proton, it forms a phenoxide ion (C6H5O-), which is stabilized by resonance. This makes phenol relatively acidic.
- **Formic Acid**: It is a stronger acid than phenol because the formate ion (HCOO-) formed after losing a proton is stabilized by resonance.
- **Benzoic Acid**: It is also acidic, but due to the +R (resonance) effect from the benzene ring, it is less acidic than formic acid.
- **Ethyl Alcohol**: It does not release protons easily, making it the least acidic of the four.

3. **Rank the Acids by Strength:**
- **Most Acidic**: Formic Acid (HCOOH)
- **Second Most Acidic**: Benzoic Acid (C6H5COOH)
- **Third Most Acidic**: Phenol (C6H5OH)
- **Least Acidic**: Ethyl Alcohol (C2H5OH)

4. **Convert Acidic Strength to pH Order:**
- Since pH is inversely related to acidity, we arrange them in decreasing order of pH:
- Ethyl Alcohol (highest pH)
- Benzoic Acid
- Formic Acid
- Phenol (lowest pH)

### Final Order of pH in Decreasing Order:
1. Ethyl Alcohol (C2H5OH)
2. Benzoic Acid (C6H5COOH)
3. Formic Acid (HCOOH)
4. Phenol (C6H5OH)