Chemistry S & P Block Elements NUMS 2022
PMDC Verified Question 61 of 104
The solubility of alkaline earth metal
A
Decreases down the group
B
Increases down the group
C
Remains constant throughout the group
D
First increases then decrease down the group
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Increases down the group
Concept:

Note: The original question stem is incomplete, but based on the provided answer key and standard chemical trends, it refers to the solubility of Alkaline Earth Metal Hydroxides.

Solution:

  • For Group II-A hydroxides (e.g., \( \text{Be(OH)}_2, \text{Mg(OH)}_2, \dots, \text{Ba(OH)}_2 \)), solubility increases down the group.
  • As the cation gets larger (from \( \text{Be}^{2+} \) to \( \text{Ba}^{2+} \)), the lattice energy of the crystal decreases much more rapidly than the hydration energy of the ions.
  • Because the lattice becomes much easier to break apart compared to the energy released by hydration, the overall solubility increases down the group.


Why other options are incorrect:

  • If the question had specified sulphates or carbonates, the answer would be "decreases down the group." However, the official key specifies Option B, confirming it is querying the hydroxide trend.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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