`CrO_3` dissolves in aqueous NaOh to give

Options

A. `CrO_4^(2-)`
B. `Cr(OH)_2`
C. `Cr_2O_7^(2-)`
D. `Cr(OH)_3`

Answer

To solve the question of what `CrO_3` (chromium trioxide) produces when it dissolves in aqueous `NaOH` (sodium hydroxide), we can follow these steps:

### Step 1: Write the Reactants
We start with the reactants in the equation:
- Chromium trioxide: `CrO_3`
- Sodium hydroxide: `NaOH`

### Step 2: Identify the Reaction
When `CrO_3` is dissolved in `NaOH`, it undergoes a chemical reaction. Chromium trioxide is an acidic oxide, and it reacts with the strong base `NaOH` to form a chromate ion.

### Step 3: Write the Balanced Chemical Equation
The balanced chemical equation for the reaction is:
\[ CrO_3 + 2 NaOH \rightarrow Na_2CrO_4 + H_2O \]
In this equation:
- `Na_2CrO_4` is the product formed, which contains the chromate ion `CrO_4^{2-}`.
- Water (`H_2O`) is also produced as a byproduct.

### Step 4: Identify the Product
From the balanced equation, we can see that the main product formed when `CrO_3` dissolves in `NaOH` is the chromate ion:
- `CrO_4^{2-}` (chromate ion)

### Conclusion
Thus, when `CrO_3` dissolves in aqueous `NaOH`, it produces the chromate ion `CrO_4^{2-}` along with water.

### Final Answer
The correct answer is: `CrO_4^{2-}`.

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