Arrange the following compounds in the increasing order of their acid strengths :
4-nitrophenol, phenol, 2,4,6-trinitrophenol.

Explanation

To arrange the compounds 4-nitrophenol, phenol, and 2,4,6-trinitrophenol in increasing order of their acid strengths, we can follow these steps:

### Step 1: Understand the Structures
1. **Draw the structures of the compounds**:
- **4-Nitrophenol**: A phenol molecule with a nitro group (NO2) at the para position (4th carbon).
- **Phenol**: A benzene ring with a hydroxyl group (OH) attached.
- **2,4,6-Trinitrophenol**: A phenol molecule with three nitro groups at the 2nd, 4th, and 6th positions.

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