Chemistry Solids ETEA 2022
PMDC Verified Question 37 of 54
Which one of the following pairs of compounds is not isomorphic in nature?
A
\( \text{NaF} \) and \( \text{MgO} \)
B
\( \text{KNO}_3 \) and \( \text{NaNO}_3 \)
C
\( \text{ZnO} \) and \( \text{CdS} \)
D
\( \text{AgNO}_3 \) and \( \text{KNO}_3 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \( \text{AgNO}_3 \) and \( \text{KNO}_3 \)
Concept:
Isomorphism refers to the phenomenon where two different chemical substances exhibit the same crystalline structure. Isomorphs typically share the same atomic ratio and similar chemical formulas.

Solution:
  • While \( \text{AgNO}_3 \) and \( \text{KNO}_3 \) share the same 1:1:3 atomic ratio, they do not share the exact same geometric crystal structure.
  • Despite their similar formulas, their differing ionic radii and structural packing prevent them from being true isomorphs.
  • Therefore, \( \text{AgNO}_3 \) and \( \text{KNO}_3 \) are NOT isomorphic.


Why other options are incorrect:
  • A, B, C: These pairs commonly exhibit isomorphism, crystallizing in matching geometric lattice systems.

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