`CrO_3` is an acidic hydride of .............

Explanation

To determine the acidic hydride of \( \text{CrO}_3 \), we can follow these steps:

### Step 1: Understand the term "acidic anhydride"
An acidic anhydride is formed when water is removed from an acid. It typically reacts with water to form an acid.

### Step 2: Identify the acid related to \( \text{CrO}_3 \)
The compound \( \text{CrO}_3 \) is derived from chromic acid, which is represented as \( \text{H}_2\text{CrO}_4 \).

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