Chemistry Solids BUMHS 2023
PMDC Verified Question 26 of 54
The system in which three angles and axes are unequal is called?
A
Cubic system
B
Triclinic system
C
Orthorhombic system
D
Trigonal system
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Triclinic system
Concept:
Crystal systems are identified by their degrees of symmetry, mapped by the equality of their edge lengths (axes) and angles.

Solution:
  • The most asymmetric crystal system is the triclinic system.
  • In a triclinic unit cell, all three axes are of different lengths (\( a \neq b \neq c \)).
  • Furthermore, all three interfacial angles are different from each other, and none are equal to 90 degrees (\( \alpha \neq \beta \neq \gamma \neq 90^\circ \)).


Why other options are incorrect:
  • A: Cubic has all equal axes and all 90-degree angles.
  • C: Orthorhombic has unequal axes, but all angles are strictly 90 degrees.
  • D: Trigonal (rhombohedral) has equal axes and equal angles (but not 90 degrees).

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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