Which of the following statements for the reaction, is correct ?
`Na_2CrO_4+H_2SO_4 to`

Options

A. It is redox reaction in which green solution of `[Cr(H_2O)_6]^(+3)`is produced.
B. One of the product in reaction has trigonal planar structure.
C. Dimeric bridged tetrahedral metal ion is produced.
D. Dark blue colour is obtained in reaction.

Explanation

To determine the correct statement regarding the reaction of sodium chromate (Na2CrO4) with sulfuric acid (H2SO4), we can analyze the reaction step by step.

### Step 1: Write the balanced chemical equation
The reaction between sodium chromate and sulfuric acid can be represented as follows:

\[ 2 \, \text{Na}_2\text{CrO}_4 + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{Cr}_2\text{O}_7 + \text{Na}_2\text{SO}_4 + \text{H}_2\text{O} \]

### Step 2: Identify the products
From the balanced equation, we can see that the products of the reaction are sodium dichromate (Na2Cr2O7), sodium sulfate (Na2SO4), and water (H2O).

### Step 3: Analyze the color of the products
Sodium dichromate (Na2Cr2O7) is known for its distinct red-orange color. This is important for evaluating the correctness of the statements provided.

### Step 4: Evaluate each statement
1. **First Statement**: It is a redox reaction in which a green solution of this complex is formed.
- **Evaluation**: This statement is incorrect because the product is red-orange (Na2Cr2O7), not green.

2. **Second Statement**: One of the products of the reaction has trigonal planar geometry.
- **Evaluation**: This statement is also incorrect. The geometry of sodium dichromate (Na2Cr2O7) is tetrahedral, not trigonal planar.

3. **Third Statement**: A dimeric bridged tetrahedral metal ion is produced.
- **Evaluation**: This statement is correct. The structure of Na2Cr2O7 shows that the chromium atoms are bridged by oxygen atoms, forming a dimeric structure with tetrahedral coordination.

4. **Fourth Statement**: A dark blue color is obtained in the reaction.
- **Evaluation**: This statement is incorrect. The color of the product is red-orange, not dark blue.

### Conclusion
Based on the evaluations, the correct statement regarding the reaction is the **third statement**, which states that a dimeric bridged tetrahedral metal ion is produced.

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