AIIMS AIIMS Solved Paper-2004

The crystal system of a compound with unit cell dimensions \[Al{{(OH)}_{3}}\]and\[C{{N}^{-}}\] and \[C{{u}^{+}}\]and \[A{{g}^{+}}\]is:

A) cubic

B)                        hexagonal

C)        orthorhombic

D)        rhombohedral

Correct Answer: B

Solution :

For the given crystal \[[Co{{(N{{H}_{3}})}_{3}}C{{l}_{3}}]\] These are the characteristic of a hexagonal system.

Crystal class	Axial distance	Axial angle	Possible type of unit cells
Cubic	\[{{[Co{{(en)}_{3}}]}^{3+}}\]	\[[Co{{(en)}_{2}}C{{l}_{2}}]Cl\]	primitive, body centred, face centred
Tetragonal	\[[Co(en){{(N{{H}_{3}})}_{2}}C{{l}_{2}}]Cl\]	\[Br>F\]	Primitive body centred
Orthorhombic	\[F>Cl\]	\[Br>Cl\]	Primitive, body centred, face centred, end centred
Hexagonal	\[F>I\]	\[{{O}_{2}}{{F}_{2}}\]	Primitive
Trigonal or Rhombohedral	\[{{C}_{2}}{{F}_{2}}\]	\[{{H}_{2}}{{O}_{2}}\]	Primitive
Monoclinic	\[{{H}_{2}}{{F}_{2}}\]	\[{{C}_{2}}{{H}_{2}}\]	Primitive and endcentred
Triclinic	\[Ga\]	\[Al\]	primitive