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Decomposition temperature of CaCO(3)(s) ...

Decomposition temperature of `CaCO_(3)(s)` is approximately `900^(@)C`. Which of the following decompose below `900^(@)C`?

A

`BeCO_(3),MgCO_(3)`

B

`SrCO_(3),BaCO_(3)`

C

`BeCO_(3),BaCO_(3)`

D

`MgCO_(3),SrCO_(3)`

Text Solution

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The correct Answer is:
To determine which compounds decompose below the decomposition temperature of calcium carbonate (CaCO₃), which is approximately 900°C, we need to analyze the thermal stability of various compounds. The key points to consider are: 1. **Understanding Decomposition**: Calcium carbonate decomposes upon heating into calcium oxide (CaO) and carbon dioxide (CO₂). The stability of a compound can be inferred from its decomposition temperature. 2. **Covalent vs Ionic Compounds**: Covalent compounds tend to be less thermally stable than ionic compounds due to weaker bonds. Therefore, we need to identify covalent compounds among the options provided. 3. **Group 2 Elements**: The question hints at elements from Group 2 of the periodic table (alkaline earth metals). The thermal stability of their carbonates decreases as we move up the group. This means that beryllium and magnesium carbonates are less stable compared to calcium carbonate. 4. **Fajans' Rule**: According to Fajans' rule, smaller cations exhibit more covalent character. Therefore, beryllium (Be²⁺) and magnesium (Mg²⁺) are smaller than calcium (Ca²⁺) and will have a higher covalent character, making their carbonates less stable and likely to decompose at lower temperatures. 5. **Comparing Sizes**: Beryllium and magnesium ions are smaller than calcium ions. Thus, their carbonates (BeCO₃ and MgCO₃) are expected to decompose at temperatures below 900°C. ### Step-by-Step Solution: 1. **Identify the Decomposition Temperature of CaCO₃**: - CaCO₃ decomposes at approximately 900°C. 2. **Consider the Group 2 Carbonates**: - The carbonates of beryllium (BeCO₃), magnesium (MgCO₃), calcium (CaCO₃), strontium (SrCO₃), and barium (BaCO₃) need to be evaluated. 3. **Analyze the Stability**: - Beryllium and magnesium carbonates are expected to be less stable than calcium carbonate due to their smaller ionic sizes and higher covalent character. 4. **Conclusion**: - Therefore, BeCO₃ and MgCO₃ are likely to decompose below 900°C. 5. **Final Answer**: - The compounds that decompose below 900°C are Beryllium carbonate (BeCO₃) and Magnesium carbonate (MgCO₃).
To determine which compounds decompose below the decomposition temperature of calcium carbonate (CaCO₃), which is approximately 900°C, we need to analyze the thermal stability of various compounds. The key points to consider are: 1. **Understanding Decomposition**: Calcium carbonate decomposes upon heating into calcium oxide (CaO) and carbon dioxide (CO₂). The stability of a compound can be inferred from its decomposition temperature. 2. **Covalent vs Ionic Compounds**: Covalent compounds tend to be less thermally stable than ionic compounds due to weaker bonds. Therefore, we need to identify covalent compounds among the options provided. 3. **Group 2 Elements**: The question hints at elements from Group 2 of the periodic table (alkaline earth metals). The thermal stability of their carbonates decreases as we move up the group. This means that beryllium and magnesium carbonates are less stable compared to calcium carbonate. ...
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