Which of the following decomposes at highest temperature?

Options

A. `SrCO_(3)`
B. `BaCO_(3)`
C. `CaCO_(3)`
D. `MgCO_(3)`

Explanation

To determine which alkaline earth metal carbonate decomposes at the highest temperature, we can follow these steps:

### Step 1: Identify the Carbonates
List the carbonates of alkaline earth metals that we are considering:
- Magnesium carbonate (MgCO3)
- Calcium carbonate (CaCO3)
- Strontium carbonate (SrCO3)
- Barium carbonate (BaCO3)

### Step 2: Understand Thermal Decomposition
Recognize that alkaline earth metal carbonates decompose upon heating to form metal oxides and carbon dioxide gas. The general reaction can be represented as:
\[ \text{MCO}_3 \rightarrow \text{MO} + \text{CO}_2 \]
where M represents the alkaline earth metal.

### Step 3: Analyze Thermal Stability
Note that the thermal stability of these carbonates increases as we move down the group in the periodic table. This means that the temperature required for decomposition increases.

### Step 4: List Decomposition Temperatures
Based on known data, we can list the approximate decomposition temperatures for each carbonate:
- Magnesium carbonate (MgCO3): ~813 K
- Calcium carbonate (CaCO3): ~1173 K
- Strontium carbonate (SrCO3): ~1563 K
- Barium carbonate (BaCO3): ~1633 K

### Step 5: Compare the Temperatures
From the temperatures listed, we can see that:
- MgCO3 decomposes at the lowest temperature.
- CaCO3 decomposes at a higher temperature than MgCO3.
- SrCO3 decomposes at a higher temperature than CaCO3.
- BaCO3 decomposes at the highest temperature among the four.

### Step 6: Conclusion
Based on the analysis, we conclude that **Barium carbonate (BaCO3)** decomposes at the highest temperature of approximately 1633 K.

### Final Answer
**Barium carbonate (BaCO3) decomposes at the highest temperature.**

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