Arrange the following in increasing order of reactivity :
`HCHO, CH_(3)CHO` AND `C_(6)H_(5)CHO `

Explanation

To arrange the compounds HCHO (formaldehyde), CH₃CHO (acetaldehyde), and C₆H₅CHO (benzaldehyde) in increasing order of reactivity, we need to consider two main factors: the positive charge on the carbonyl carbon and steric hindrance.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- HCHO: Formaldehyde
- CH₃CHO: Acetaldehyde
- C₆H₅CHO: Benzaldehyde
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