Question

Which of the following is correct?

• A. Crystal system - Cubic Axial Distance - $a \neq b=c$ Axial angles $-\alpha=\beta \neq \gamma$ Examples -$Cu, KCl$
• B. Crystal system - Monoclinic Axial Distance - $\alpha \neq b=c$ Axial angles - $\alpha \neq \beta=\gamma$ $=90^{\circ}$ Examples - $p b C r O_{2}, p b C r O_{4}$
• C. Crystal system - Rhombohedral Axial Distance $-a=b=c$ Axial angles - $\alpha=\beta=\gamma \neq 90^{\circ}$ Examples - $CaCO _{3}$, Hgs
• D. Crystal system - Triclinic Axial Distance - $a = b = c$ Axial angles $-\alpha \neq \beta=\gamma \neq 90^{\circ}$ Examples - $K _{2}\, Cr _{2} \,O _{7}\, CuSO _{4} \,5 H _{2} O$

Answer 1

Answer: (C)

Crystal system - Rhombohedral Axial Distance $-a=b=c$ Axial angles - $\alpha=\beta=\gamma \neq 90^{\circ}$ Examples - $CaCO _{3}$, Hgs

Answer 2

[a] For cubic $a=b=c$ and $a=\beta=\gamma=90^{\circ}$ So, it is wrong. [b] For monoclinic $a \neq b \neq c$ and $\alpha=\gamma=90^{\circ}$ and $\beta \neq 90^{\circ}$ $\therefore$ is wrong. [c] For triclinic $a \neq b \neq c$ and $\alpha \neq \beta \neq \gamma \neq 90^{\circ}$ $\therefore$ It iswrong. [d] For rhombohedral crystal system $a=b=c$ and $\alpha=\beta=\gamma \neq 90^{\circ}$.