Chemistry Solids BUMHS 2022
PMDC Verified Question 40 of 54
Which one of the following is not a crystalline solid?
A
Copper sulphate
B
Sugar
C
\( \text{NaCl} \)
D
Rubber
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Rubber
Concept:
Crystalline solids possess a highly regular, repeating 3D arrangement of atoms. Amorphous solids have irregular, random arrangements.

Solution:
  • Rubber is a polymer composed of long, tangled molecular chains.
  • It lacks a regular, repeating internal geometric lattice.
  • Because its structural arrangement is random and disordered, rubber is classified as an amorphous (non-crystalline) solid.


Why other options are incorrect:
  • A, C: Copper sulphate and Sodium chloride are classic ionic crystalline solids.
  • B: Sugar (sucrose) is a polar molecular crystalline solid.

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