Which of the following statements about the elements, Mg, Ca, Sr and Ba and their compounds is true?

Options

A. Solubility of the hydroxides in water increase with increasing atomic number
B. Thermal stability of the carbonates increase with increasing atomic number
C. All given elements react with water or steam to give hydrogen
D. Metal chloride are all liqiuds at room temperature

Answer

To determine which statement about the elements Mg, Ca, Sr, and Ba and their compounds is true, we will analyze each statement step by step.

### Step 1: Analyze Statement A
**Statement A:** The solubility of hydroxides in water increases with increasing atomic number.

- **Explanation:** As we move down the group from Mg to Ba, the atomic radius increases. This larger size makes it easier for the hydroxides to dissolve in water. Therefore, the solubility of hydroxides indeed increases with increasing atomic number.

**Conclusion:** Statement A is true.

### Step 2: Analyze Statement B
**Statement B:** The thermal stability of carbonates increases with increasing atomic number.

- **Explanation:** The thermal stability of carbonates generally increases down the group. For example, while MgCO3 decomposes at a lower temperature, BaCO3 is more stable and decomposes at a higher temperature. This trend is due to the increasing size of the cation, which stabilizes the carbonate ion.

**Conclusion:** Statement B is true.

### Step 3: Analyze Statement C
**Statement C:** The given elements react with water or steam to give hydrogen.

- **Explanation:** All the mentioned alkaline earth metals (Mg, Ca, Sr, Ba) react with water or steam to produce hydrogen gas. For example, Mg reacts with water to form magnesium hydroxide and hydrogen gas. Similarly, Ca, Sr, and Ba react with water to produce their respective hydroxides and hydrogen.

**Conclusion:** Statement C is true.

### Step 4: Analyze Statement D
**Statement D:** Metal fluorides are all liquid at room temperature.

- **Explanation:** This statement is incorrect. The metal fluorides of Mg, Ca, Sr, and Ba are all solid at room temperature. None of them exist as liquids under standard conditions.

**Conclusion:** Statement D is false.

### Final Conclusion
After analyzing all statements:
- Statement A: True
- Statement B: True
- Statement C: True
- Statement D: False

The true statements about the elements Mg, Ca, Sr, and Ba and their compounds are A, B, and C.

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