Which of the following is not a correct order of solubility in water :-

Options

A. `LiOH lt NaOH lt KOH lt RbOH `
B. `AgF gt AgCl gt AgBr gt AgI`
C. `BeF_(2) lt BeCl_(2) lt BeBr_(2) lt BeI_(2)`
D. `BeSO_(4) gt MgSO_(4) gt CaSO_(4) gt BaSO_(4)`

Explanation

To determine which of the following orders of solubility in water is incorrect, we will analyze the solubility of different compounds based on their ionic character, size of ions, and general solubility trends.

### Step-by-Step Solution:

1. **Understanding Hydroxides of Alkali Metals:**
- Alkali metal hydroxides (LiOH, NaOH, KOH, etc.) become more soluble in water as you move down the group. This is because the ionic character increases with the size of the metal ion.
- **Conclusion:** This order is correct.

2. **Analyzing Silver Halides:**
- Silver halides (AgCl, AgBr, AgI) have solubility that is inversely related to the size of the anion. Larger anions lead to lower ionic character and thus lower solubility.
- The order of solubility is AgF > AgCl > AgBr > AgI, as Iodide is the largest and least soluble.
- **Conclusion:** This order is also correct.

3. **Examining Halides of Beryllium:**
- Beryllium halides (BeF2, BeCl2, BeBr2, BeI2) also follow a trend where the ionic character is inversely proportional to the size of the anion. The order of ionic character (and thus solubility) is BeF2 > BeCl2 > BeBr2 > BeI2.
- The order given in the question may state BeI2 as the most soluble, which is incorrect.
- **Conclusion:** This order is incorrect.

4. **Checking Solubility of Group 2 Sulfates:**
- For group 2 sulfates (BeSO4, MgSO4, CaSO4, SrSO4, BaSO4), the solubility generally decreases as the size of the cation increases.
- The order of solubility is BeSO4 > MgSO4 > CaSO4 > SrSO4 > BaSO4.
- **Conclusion:** This order is correct.

### Final Answer:
The incorrect order of solubility in water is related to the halides of beryllium, where BeI2 is incorrectly stated as the most soluble.