Which does not represent correct method?

Options

A. `TiCl_2 + 2Mg to Ti + 2MgCl_2`, Kroll
B. `Ni(CO)_4 to Ni + 4CO` , Mond
C. `Ag_2CO_3 to 2Ag+CO_2+1/2 O_2` : Van Arkel
D. `Zrl_4 to Zr + 2I_2` , Van Arkel

Explanation

To determine which option does not represent a correct method, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze Option A:**
- Reaction: \( \text{TiCl}_4 + 2 \text{Mg} \rightarrow \text{Ti} + 2 \text{MgCl}_2 \)
- This reaction represents the **Kroll process**, which is indeed a correct method for the reduction of titanium tetrachloride (TiCl4) to titanium (Ti) using magnesium (Mg).

2. **Analyze Option B:**
- Reaction: \( \text{Ni(CO)}_4 \rightarrow \text{Ni} + 4 \text{CO} \)
- This reaction represents the **Mond process** (also known as the Mond method), which is a correct method for the extraction of nickel from its carbonyl complex.

3. **Analyze Option C:**
- Reaction: \( \text{CaCO}_3 \rightarrow 2 \text{Ag} + \text{CO}_2 + \frac{1}{2} \text{O}_2 \)
- This reaction does not represent a specific known method for extracting silver. It appears to be a calcination reaction rather than a method like the Van Arkel process or any other known extraction method.

4. **Analyze Option D:**
- Reaction: \( \text{ZrI}_4 + 2 \text{I}_2 \rightarrow \text{Zr} + 2 \text{I}_2 \)
- This reaction represents the **Van Arkel process**, which is a correct method for the purification of zirconium.

### Conclusion:
Among the options analyzed, **Option C** does not represent a correct method for extracting silver. Therefore, the answer is:

**Option C is the correct answer.**

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