Multiple Choice QuestionsWhich statement is not true for metals?
They form bcc structure
They form hcp structure
They form ccp structure
They have low enthalpy of sublimation
The cubic unit cell of a metal (molar mass = 63.55g mol-1) has an edge length of 362 pm. Its density is 8.92 g cm-3 . The type of unit cell is
primitive
face- centred
body centred
end centred
The flame colours of metal ions are due to
Frenkel defect
Schottky defect
Metal deficiency defect
Metal excess defect
D.
Metal excess defect
Flame colours are due to metal excess defect. What happens that in some ionic crystals, there becomes an excess of metal atom, which by loosing e-, change into ions. These electrons can absorb energy and go into excited states from ground state. Thus the absorption of certain wavelength of light takes place and crystal becomes coloured according to complementary colour. The spaces occupied by extra e- are called F-centres.
Which one of the following statements about amorphous solids is incorrect?
They melt over a range of temperature
They are anisotropic
There is no orderly arrangement of particles
They are rigid and incompressible
If the distance between Na+ and Cl- ionsin sodium chloride crystal is X pm, the length of the edge of the unit cell is
4X pm
X/4 pm
X/2 pm
2 X pm
Which of the following does not conduct electricity?
Fused NaCl
Solid NaCl
Brine solution
Copper
Which one of the following defects in the crystals lowers its density?
Frenkel defect
Schottky defect
F-centres
Interstitial defect
The radii of Na+ and Cl- ions are 95 pm and 181 pm respectively. The edge length of NaCl unit cell is :
276 pm
138 pm
552 pm
415 pm
Malleability and ductility of metals can be accounted due to
the presence of electrostatic force
the crystalline structure in metal
the capacity of layers of metal ions to slide over the other
the interaction of electrons with metal ions in the lattice
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