Which of the following bicarbonate can exist in solid state :-

Options

A. `LiHCO_(3)`
B. `Mg(HCO_(3))_(2)`
C. `Zn(HCO_(3))_(2)`
D. `KHCO_(3)`

Explanation

To determine which bicarbonate can exist in solid state, we need to analyze the properties of bicarbonates formed by different metals, particularly focusing on alkali metals.

### Step-by-Step Solution:

1. **Understand Bicarbonates**: Bicarbonates are salts containing the bicarbonate ion (HCO3^-). They can be formed from various metals.

2. **Identify Alkali Metals**: The alkali metals are found in Group 1 of the periodic table, which includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

3. **General Rule for Bicarbonates**: Generally, the bicarbonates of alkali metals can exist in solid state due to their high electropositive nature. This means they can form stable ionic compounds with the bicarbonate ion.

4. **Exception - Lithium Bicarbonate**: However, there is an important exception: lithium bicarbonate (LiHCO3) does not exist in solid state. This is due to the small size of the lithium ion and its relatively high electronegativity compared to other alkali metals. These properties make lithium bicarbonate less ionic and thus less stable in solid form.

5. **Evaluate Other Bicarbonates**: The bicarbonates of other alkali metals (sodium, potassium, rubidium, cesium) can exist in solid state because they are larger cations and have lower electronegativities, leading to more stable ionic compounds.

6. **Conclusion**: Among the options provided, the only bicarbonate that can exist in solid state is potassium bicarbonate (KHCO3), as it is a bicarbonate of an alkali metal that does not have the same stability issues as lithium bicarbonate.

### Final Answer:
The bicarbonate that can exist in solid state is **Potassium Bicarbonate (KHCO3)**.

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