On heating which of the following release `CO_(2)` most easily ?

Options

A. `K_2CO_3`
B. `Na_2CO_3`
C. `MgCO_3`
D. `CaCO_3`

Explanation

To determine which compound releases CO2 most easily upon heating, we need to analyze the thermal stability of the given carbonates: K2CO3, Na2CO3, MgCO3, and CaCO3.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four carbonates to consider:
- K2CO3 (Potassium Carbonate)
- Na2CO3 (Sodium Carbonate)
- MgCO3 (Magnesium Carbonate)
- CaCO3 (Calcium Carbonate)

2. **Understand Thermal Stability**: The thermal stability of a carbonate generally depends on the size and charge of the cation. Smaller cations with higher charges tend to form more stable carbonates, which do not decompose easily upon heating.

3. **Analyze Each Compound**:
- **K2CO3**: Potassium ion (K+) is larger and has a +1 charge, making K2CO3 relatively stable.
- **Na2CO3**: Sodium ion (Na+) is also larger with a +1 charge, thus Na2CO3 is stable as well.
- **CaCO3**: Calcium ion (Ca²+) is larger than Mg²+ but has a +2 charge, which makes CaCO3 more stable than the +1 charged carbonates.
- **MgCO3**: Magnesium ion (Mg²+) is smaller and has a +2 charge. The combination of a small cation with a carbonate ion (CO3²-) leads to a less stable compound.

4. **Determine Decomposition**: Upon heating, carbonates decompose to form metal oxides and CO2. The less thermally stable the carbonate, the more readily it will decompose:
- **MgCO3** decomposes to MgO and releases CO2 easily due to its instability.
- The other carbonates (K2CO3, Na2CO3, and CaCO3) are more thermally stable and do not release CO2 as readily.

5. **Conclusion**: Among the given options, **MgCO3** is the least thermally stable and thus releases CO2 most easily upon heating.

### Final Answer:
**MgCO3** releases CO2 most easily upon heating.

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