Which among the following is a false statement ?

Options

A. `SiO_2` has a structure similar to that of `CO_2`
B. Natural Si exists only in the combined state
C. Si can be prepared by reducing `SiO_2` with Mg.
D. Si does exist in graphite - like structure , but exists only in diamond like structure

Answer

To determine which statement among the given options is false, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement A: SiO2 structure is similar to that of CO2.**
- **Analysis**: CO2 is a linear molecule (O=C=O), whereas SiO2 has a tetrahedral structure due to the sp3 hybridization of silicon. In SiO2, each silicon atom is bonded to four oxygen atoms in a three-dimensional network. Therefore, this statement is **false**.

2. **Statement B: Natural silicon exists only in the combined state.**
- **Analysis**: Natural silicon is primarily found in the form of silicon dioxide (SiO2) and silicates in nature, meaning it is mostly in a combined state. Thus, this statement is **true**.

3. **Statement C: Si can be prepared by reducing SiO2 with Mg.**
- **Analysis**: The reduction of SiO2 with magnesium does yield silicon and magnesium oxide (MgO). The balanced reaction is:
\[ \text{SiO2} + 2\text{Mg} \rightarrow \text{Si} + 2\text{MgO} \]
- This statement is therefore **true**.

4. **Statement D: Silicon exists in a graphite-like structure but exists only in a diamond-like structure.**
- **Analysis**: Silicon does not have a graphite-like structure. It primarily exists in a diamond-like structure (cubic crystalline form). Therefore, this statement is **true**.

### Conclusion:
The false statement among the options is **Statement A: SiO2 structure is similar to that of CO2.**

---