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
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
Which of the following unit cell having maximum number of atoms ?
BCC
HCP
FCC
Cubic
C.
FCC
Among the given options, FCC has maximum number of atoms. Atoms are present at 8 corners of cube and 1 at centre of each face. It can be calculated as-
No. of atoms in fcc = 8 × × 6 = 1 + 3 = 4
In HCP, atoms in crystals are packed in ABAB pattern.
In BCC, atoms are present at 8 corners of cube and one atom is present at the centre of body of cube.
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
AB is an ionic solid. The ionic radii of A+ and B- are respectively rc and ra. Lattice energy of AB is proportional to :
(rc + ra)
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
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
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.