Question

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

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $R$ is correct; $A$ is incorrect.

Answer 1

Answer: (D)

Like quartz and ice, graphite is an example of hexagonal system.
For this $\alpha=\beta=90^{\circ}$ and
$\gamma=120^{\circ}$ and $a=b \neq c$.
For a tetragonal system $\alpha=\beta=\gamma=90^{\circ}$
and $a=b \neq c$.