Solubility trends of Group 2 nitrates and sulfates

Steps:

• Group 2 nitrates are all soluble; solubility increases down the group as cation size increases, reducing charge density and lattice energy more than hydration energy.
• Group 2 sulfates show decreasing solubility down the group; larger cations lower hydration energy faster than lattice energy, making sulfates less soluble.
• Match trends to options: nitrates increase (options C, D), sulfates decrease (options B, D).
• Select option combining both correct trends.

Why D is correct:

• Aligns with Fajans' rules and Born-Haber cycle: for nitrates (large anion), increasing cation size boosts solubility; for sulfates (smaller anion), it reduces solubility due to hydration energy drop.

Why the others are wrong:

• A: Nitrates do not decrease; all are highly soluble and increase slightly down group.
• B: Nitrates increase, not decrease down group.
• C: Sulfates decrease, not increase down group.

Final answer: D