12ECHMS33

• Orthorhombic

• Triclinic

• Hexagonal

• Tetragonal

An example of network solid is ?

• BN

• Cu

• ZnS

• P₄

Solid Xe has a crystal structure built on fcc unit cells. If Xe atom has a radius of 219.2pm, then the length of the face-diagonal of the unit cell in its crystal is?

• 438.4pm

• 657.6pm

• 876.8pm

• 763.2pm

Each side of the unit cell of NaCl crystal has a length of 552 pm. If radius of Na⁺ be 95 pm, then radius of Cl^- is ............ ?

• 457pm

• 181pm

• 362pm

• 305pm

The crystal structure of an element is based on face-centered cubic unit cell with an edge length of 'a' cm. The packing efficiency of a face-centered cubic unit cell is 74%. If each atom of the element has a volume of x cm^{3 ,} then the relation between ' a' and ' x' is ........ ?

The substance whose crystalline form is quartz, is?

• Silicon

• Sodium silicate

• Silicon carbide

• Silica

After melting quartz a polycrystalline substance is formed if it is cooled very rapidly?

• An amorphous solid is formed

• Its crystalline structure remains the same

• A colloidal substance is formed

In which of the following cases the example as mentioned does not refer to the solid?

• Molecular solid: solid SO2

• Covalent solid: SiC

• Metallic solid: Mg

Of the crystal systems given below, which one has more than one Bravais lattices?

• Triclinic

• Monoclinic

• Rhombohedral

• Hexagonal

Which one of the following comments about quartz is true?

• It is anisotropic

• It is a supercooled liquid with high viscosity

• It melts over a range of temperature

• All are true