Chemistry S & P Block Elements SZABMU 2024
PMDC Verified Question 6 of 104
Which of the following metal hydroxide is the strongest base?
A
\( \text{Ca(OH)}_2 \)
B
\( \text{Mg(OH)}_2 \)
C
LiOH
D
NaOH
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: NaOH
Concept:

The strength of a base depends on how fully it dissociates in water to release hydroxide ions (\( \text{OH}^- \)). Highly soluble hydroxides of metals with low ionization energies make the strongest bases.

Solution:

  • Group 1 vs Group 2: Alkali metals (Group 1) have larger radii and lower ionization energies than Alkaline earth metals (Group 2). Thus, Group 1 hydroxides are far more soluble and dissociate more completely than Group 2 hydroxides (like Mg(OH)2 or Ca(OH)2).
  • Within Group 1 (LiOH vs NaOH): Lithium is very small, meaning the Li-O bond has strong lattice energy and partial covalent character, limiting its dissociation compared to Sodium.
  • Sodium (Na) is larger, making NaOH highly ionic and overwhelmingly soluble in water.
  • Because it completely dissociates in aqueous solution, NaOH provides the highest concentration of \( \text{OH}^- \) ions, making it the strongest base among the choices.


Why other options are incorrect:

  • \( \text{Mg(OH)}_2 \) is highly insoluble (used in antacids because it is a weak base). \( \text{Ca(OH)}_2 \) is only sparingly soluble. LiOH is the weakest base in Group 1.

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