121.

Which of the following when dissolved in water forms a solution, i.e, non-conducting?

• Chile salt petre

• Potash alum

• Green vitriol

• ethyl alcohol

In NaCl crystal each Cl^- ion is surrounded by

• 4 Na⁺ ions

• 6 Na⁺ ions

• 1 Na⁺ ions

• 2 Na⁺ ions

The radius ratio in CsCl is 0.93. The expected lattice structure is

• tetrahedral

• square planar

• octahedral

• body-centred cubic

Which defect causes decrease in the density of crystal?

• Frenkel

• Schottky

• Interstitial

• F - centre

The lattice points of a crystal of hydrogen iodide are occupied by

• HI molecules

• H atoms and I atoms

• H⁺ cations and I^- anions

• H₂, molecules and I₂ molecules

The number of octahedral sites per sphere in a fcc structure is

• 1

• 2

• 4

• 8

Ice crystallises in a hexagonal lattice. At the low temperature, the lattice constants were a = 4.53 Å and b = 7.41 Å. How many H₂O molecules are contained in a unit cell? [d(ice) =0.92 g /cm³ ]

• 4

• 3

• 2

• 1

Calculate the ionic radius of a Cs⁺ ion, assuming that the cell edge lenght for CsCl is 0.4123 nm and that the ionic radius of a Cl^- ion is 0.181 nm

• 0.176 nm

• 0.231 nm

• 0.357 nm

• 0.166 nm

Which one is not the property of crystalline solid?

• A definite and regular geometry

• High intermolecular forces

• Isotropic

• Sharp melting point

Which defect in any crystal lowers its density?

• Schottky

• Interstitial

• F- centre

• Frenkel