SOLID STATE CHEMISTRY, class 12

Which of the following conditions favours the existence of a substance in the solid state?

• high temperature

• low temperature

• high thermal energy

• weak cohesive forces

Which of the following is true about the value of refractive index of quartz glass?

• same in all directions

• different in different directions

• cannot be measured

• always zero

Which of the following statement is not about amorphous solids?

• on heating they may become crystalline at certain temperature

• they may become crystalline on keeping for long time

• amorphous solids can be moulded by heating

• they are anisotropic in nature

Which one of the following is a covalent crystal?

• rock salt

• ice

• quartz

• dry ice

Bravais lattices are of

• 7 types

• 10 types

• 14 types

• 17 types

NaCl crystal belongs to the crystal system

• hexagonal

• cubic

• tetragonal

• orthorhombic

Which of the following defects, if present, lowers the density of the crystal?

• Frenkel

• Schottky

• Edge dislocation

• Constitution of F-centres

How many number of atoms are there in a cube based unit cell having one atom on each corner and two atoms on each body diagonal of cube?

• 8

• 9

• 4

• 6

When NaCl crystal is doped with MgCl₂ the nature of defect produced is

• interstitial defect

• Schottky defect

• Frenkel defect

• None of these

In a close packed array of N spheres, the number of tetrahedral holes are

• N/2

• 4N

• 2N

• N