Q. Which of the following is correct order of solubility of sulphates of alkaline earth metals?

Options

A. `MgSO_(4) gt BeSO_(4) gt CaSO_(4) gt BaSO_(4)`
B. `BeSO_(4) gt MgSO_(4) gt CaSO_(4) gt BaSO_(4)`
C. `BaSO_(4) gt MgSO_(4) gt CaSO_(4) gt BeSO_(4)`
D. `BaSO_(4) gt CaSO_(4) gt MgSO_(4) gt BeSO_(4)`.

Answer

To determine the correct order of solubility of the sulfates of alkaline earth metals (Group 2 elements), we can follow these steps:

### Step 1: Identify the Alkaline Earth Metals
The alkaline earth metals include:
- Beryllium (Be)
- Magnesium (Mg)
- Calcium (Ca)
- Strontium (Sr)
- Barium (Ba)

### Step 2: Understand the Factors Affecting Solubility
The solubility of sulfates depends on two main factors:
1. **Lattice Energy (Lattice Enthalpy)**: The energy required to break the ionic compound into gaseous ions. Higher lattice energy means lower solubility.
2. **Hydration Enthalpy**: The energy released when ions are hydrated. Higher hydration enthalpy means higher solubility.

### Step 3: Analyze Lattice Energy
For alkaline earth metal sulfates, the lattice energy remains relatively constant as we move down the group. This is because the size of the sulfate ion (SO₄²⁻) does not change significantly, while the cation size increases slightly.

### Step 4: Analyze Hydration Enthalpy
As we move down the group from beryllium to barium:
- The size of the cation increases.
- The hydration enthalpy decreases because larger cations are less effectively hydrated due to their lower charge density.

### Step 5: Determine the Solubility Order
Since solubility is directly proportional to hydration enthalpy and inversely proportional to lattice energy, we can conclude:
- Beryllium sulfate (BeSO₄) has the highest solubility due to its high hydration enthalpy.
- Magnesium sulfate (MgSO₄) follows.
- Calcium sulfate (CaSO₄) comes next.
- Strontium sulfate (SrSO₄) is less soluble.
- Barium sulfate (BaSO₄) has the lowest solubility.

Thus, the correct order of solubility of the sulfates of alkaline earth metals is:
**BeSO₄ > MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄**

### Final Answer
The correct order of solubility of sulfates of alkaline earth metals is:
**Beryllium sulfate > Magnesium sulfate > Calcium sulfate > Strontium sulfate > Barium sulfate**

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