(d) pure rare earth metals
Ans: (b)
32. The variety of coal in which the deposit contains recognisable traces of the original plant material is: [IES 1994]
    (a) anthracite
    (b) lignite
    (c) peat
    (d) bitumen
Ans: (c)
33. The highest grade of coal whose surface is shining and has the highest calorific value, is:
    (a) Bituminous
    (b) Lignite
    (c) Anthracite
    (d) Peat
Ans: (c)
34. Diamond is harder than graphite because of:
    (a) difference of layers of atoms
    (b) tetrahedral structure of diamond
    (c) difference of crystalline structures
    (d) None of the above
Ans: (c)
35. Radioactive distintegration of uranium ultimately results in formation of:
    (a) radium
    (b) thorium
    (c) polonium
    (d) lead
Ans: (d)
36. The isotope of uranium capable of sustaining chain reactions is: [RRB 1991]
    (a) U-235
    (b) U-238
    (c) U-239
    (d) None of these
Ans: (a)
37. ‘No two electrons in an atom can have the same set of four quantum number" is : [UTI 1994]
    (a) Bohr"s law
    (b) Aufbau principle
    (c) Newton"s law
    (d) Pauli"s exclusion principle
Ans: (d)
38. The location and energy of an electron in an atom can be specified by:
    (a) atomic mass
    (b) atomic number
    (c) quantum numbers
    (d) None of the above
Ans: (c)