The correct increasing order of solubility among the compounds follows as

Options

A. `CaCO_3 lt NaHCO_3 lt KHCO_3`
B. `KHCO_3 lt NaHCO_3 lt CaCO_3 `
C. `CaCO_3 lt KHCO_3 lt NaHCO_3 `
D. `NaHCO_3 lt CaCO_3 lt KHCO_3 `

Answer

To determine the correct increasing order of solubility among the compounds Calcium carbonate (CaCO₃), Sodium bicarbonate (NaHCO₃), and Potassium bicarbonate (KHCO₃), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Compounds**: We have three compounds to compare: Calcium carbonate (CaCO₃), Sodium bicarbonate (NaHCO₃), and Potassium bicarbonate (KHCO₃).

2. **Understand the Solubility of Carbonates**:
- Carbonates of alkaline earth metals (like Calcium carbonate) are generally insoluble in water due to their high lattice energy. This means that they do not dissolve well in water.
- Therefore, we can conclude that Calcium carbonate (CaCO₃) will have the lowest solubility among the three compounds.

3. **Understand the Solubility of Bicarbonates**:
- Bicarbonates (or hydrogen carbonates) of alkali metals (like Sodium bicarbonate and Potassium bicarbonate) are generally soluble in water.
- The solubility of bicarbonates increases as we move down the group in the periodic table. This means that Sodium bicarbonate will be less soluble than Potassium bicarbonate.

4. **Compare the Solubility**:
- From the above points, we can summarize the solubility as follows:
- Calcium carbonate (CaCO₃) is the least soluble.
- Sodium bicarbonate (NaHCO₃) is more soluble than Calcium carbonate but less soluble than Potassium bicarbonate.
- Potassium bicarbonate (KHCO₃) is the most soluble among the three.

5. **Write the Increasing Order of Solubility**:
- Based on the analysis, the increasing order of solubility is:
- CaCO₃ < NaHCO₃ < KHCO₃

### Final Answer:
The correct increasing order of solubility among the compounds is:
**Calcium carbonate (CaCO₃) < Sodium bicarbonate (NaHCO₃) < Potassium bicarbonate (KHCO₃)**

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