Question

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

• 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 $a=b\ne c$.
For a tetragonal system $\alpha =\beta =\gamma =90^{\circ }$
and $a=b\ne c$.