Which of the following statements is correct ? from Chemistry Th

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 Multiple Choice QuestionsMultiple Choice Questions

51.

Invar, an alloy of Fe and Ni is used in watches and meter scale. Its characteristic property is

  • small coefficient of expansion

  • resistance of corrosion

  • hardness and elasticity

  • magnetic nature


52.

An alloy of Pb and Sn in equal proportion is called:

  • solder

  • constantan

  • gun metal

  • type metal


53.

A compound with cubic structure is made of elements A and B. A atoms are at the corners of the cube and B atoms are at the face centres. The simplest formula of the compound is :

  • A5B

  • AB3

  • AB

  • AB6


54.

Which of the following unit cell having maximum number of atoms ?

  • BCC

  • HCP

  • FCC

  • Cubic


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55.

Silicon is

  • semiconductor

  • insulator

  • conductor

  • None of these


56.

If the mass defect of a nuclide is 3.32 x 10-26g, its binding energy is ......... MeV

  • 9.31

  • 18.62

  • 27.93

  • 37.24


57.

AB is an ionic solid. The ionic radii of A+ and B- are respectively rc and ra. Lattice energy of AB is proportional to :

  • rcra

  • (rc + ra)

  • rarc

  • 1rc + ra


58.

If the mass defect of 5B11 is 0.081 u, its average binding energy (in MeV) is

  • 8.60

  • 6.85

  • 5.60

  • 5.86


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59.

Which of the following statements is correct ?

  • Silicon doped with boron is an n-type semiconductor

  • Silicon doped with arsenic is a p-type semiconductor

  • Metals are good conductors of electricity

  • Electrical conductivity of semiconductors decreases with increasing temperature


C.

Metals are good conductors of electricity

Metals are good conductors of electricity due to the presence of free electrons. Electrical conductivity of semiconductors increases with increase in temperature.


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60.

Assertion (A): White tin is an example of tetragonal system.
Reasoning (R): For a tetragonal system a= b = c and  α = β = γ ≠ 90°. The correct answer is

  • (A) and (R) are true and (R) is the correct explanation of (A).

  • Both (A) and (R) are true and (R) is not the correct explanation of (A).

  • (A) is true but (R) is not true.

  • (A) is not true but (R) is true.


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