Which of the following bicarbonate does not exist in solid state?

Options

A. `LiHCO_(3)`
B. `KHCO_(3)`
C. `CsHCO_(3)`
D. `NaHCO_(3)`

Answer

To determine which bicarbonate does not exist in solid state, we will analyze the bicarbonates of lithium, sodium, potassium, and cesium.

### Step-by-Step Solution:

1. **Identify the Bicarbonates**:
- The bicarbonates in question are:
- Lithium bicarbonate (LiHCO3)
- Sodium bicarbonate (NaHCO3)
- Potassium bicarbonate (KHCO3)
- Cesium bicarbonate (CsHCO3)

2. **Understand the Stability of Bicarbonates**:
- Bicarbonates are generally stable in solid form for alkali metals except for lithium.
- Lithium bicarbonate is unique due to its chemical properties.

3. **Diagonal Relationship**:
- Lithium exhibits a diagonal relationship with magnesium in the periodic table. This means that lithium shares some properties with magnesium, which affects the stability of its compounds.

4. **Decomposition of Lithium Bicarbonate**:
- Lithium bicarbonate (LiHCO3) does not remain stable in solid form; it decomposes upon heating or even at room temperature.
- The decomposition reaction can be represented as:
\[ 2 \, \text{LiHCO}_3 \, \rightarrow \, \text{Li}_2\text{CO}_3 + \text{CO}_2 + \text{H}_2\text{O} \]
- This reaction indicates that lithium bicarbonate breaks down into lithium carbonate, carbon dioxide, and water.

5. **Conclusion**:
- Due to this decomposition, lithium bicarbonate does not exist in solid state, unlike sodium, potassium, and cesium bicarbonates which are stable as solids.

### Final Answer:
**Lithium bicarbonate (LiHCO3) does not exist in solid state.**