Arrange the following in the increasing order of acidity:
ethanol, ethanoic acid, 4-nitrophenol, phenol.

Explanation

To arrange the given compounds (ethanol, ethanoic acid, 4-nitrophenol, and phenol) in increasing order of acidity, we need to analyze the stability of their conjugate bases after the release of a proton (H⁺). The more stable the conjugate base, the stronger the acid.

### Step-by-step Solution:

1. **Identify the Structures**:
- **Ethanol (C₂H₅OH)**: The structure is CH₃CH₂OH.
- **Ethanoic Acid (Acetic Acid, C₂H₄O₂)**: The structure is CH₃COOH.
- **4-Nitrophenol**: The structure is C₆H₄(OH)(NO₂) with the nitro group (NO₂) at the para position.
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