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 acidity of each compound based on their ability to donate protons (H\(^+\)).

### Step 1: Understand the Compounds
- **Water (\( H_2O \))**: A well-known solvent and a weak acid that can dissociate to release H\(^+\) ions.
- **Alcohol (\( ROH \))**: An alcohol where \( R \) is an alkyl group. Alcohols can also donate protons, but their acidity is influenced by the nature of the alkyl group.
- **Ethyne (\( HC \equiv CH \))**: An alkyne with a triple bond. The carbon atoms in ethyne are sp-hybridized, which affects its acidity.

### Step 2: Analyze Acidity
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