Q60 / 180 · AIIMS 2006 · Chemistry

Assertion : Graphite is an example of tetragonal crystal system. Reason : For a tetragonal system, $a=b \neq c$, $\alpha=\beta=90^{\circ}, \gamma=120^{\circ}$.

  • A
    If both assertion and reason are true and reason is the correct explanation of the assertion
  • B
    If both assertion and reason are true but reason is not the correct explanation of the assertion
  • C
    If assertion is true, but reason is false
  • Correct answer
    D
    Both assertion and reason are false statements.

Solution

Graphite has a two dimensional sheet structure. Each $\mathrm{C}$-atom is in $s p^2$ hybridised state and is linked to three other carbon atoms in a hexagonal planar structure. For a tetragonal system, $a=b \neq c, \alpha=\beta=\gamma=90^{\circ}$. For a hexagonal system, $a=b \neq c, \alpha=\beta=90^{\circ}$, $\gamma=120^{\circ}$.

Hence, the correct answer is option: 'D'.

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