Arrange the following compounds in decreasing order of acidity.
`H_(2)O, ROH, HC -= CH`

Explanation

To arrange the compounds \( H_2O \), \( ROH \), and \( HC \equiv CH \) in decreasing order of acidity, we need to analyze the stability of their conjugate bases formed upon the release of a proton (\( H^+ \)).

### Step-by-Step Solution:

1. **Identify the Compounds and Their Conjugate Bases**:
- For \( H_2O \) (water), when it donates a proton, it forms \( OH^- \) (hydroxide ion).
- For \( ROH \) (an alcohol), when it donates a proton, it forms \( RO^- \) (alkoxide ion).
- For \( HC \equiv CH \) (ethyne), when it donates a proton, it forms \( HC \equiv C^- \) (acetylide ion).
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