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1.a) Band theory is used to explain the conductivity of differentsolid crystals. Define the band width and calculate s band widthassuming there is indefinite number of molecular orbitals in the sband.

b)Explain how metallic conductor, semiconductor and insulator areidentified by band theory.

c)3.0 mol CO2behaving as a vander Waals gas, when it is confined under the following conditions:at 750 K in 150 cm3.
For CO2Van derWaals coefficients, a: 3.610 L2atmmol-2,b: 4.29x10-2Lmol-1.Gas constant R is 8.206 x 10-2L atmK-1mol-1
i) Calculate thegas pressure (in atm),

ii)What is the molar volume of the gas (in L/mol),
iii) What is thepressure when it is ideal gas and use it to state dominating forcein

theabove gas?

2.a) Use one example to describe Born-Haber cycle

b)Calculate
i) The resultant of two stationary dipole moments of magnitude 1.2Dand 1.8D that make an angle of 130oto eachother in vacuum (expressed in D)

ii)The interaction between pairs of rotating molecules withμ= 1.5Dand r =0.1 nm in one material at 325K in air (expressed inkJ/mol)

3.a) Account for two kinds of semiconductor and use schemes toexplain charge flow between n-type and p-type semiconductors in thedark condition without a bias

b)Asubstance known to have a cubic unit cell gives reflections withCu Karadiation(wavelength 154 pm) at the glancing angle of32.6o.

Thereflection is known to be due to the (220) plane. Index thereflection at the glancing angle of 39.4o
.