Q 1. Match the crystal system / unit cells mentioned in Column I with their characteristic features mentioned in Column II. Indicate your answer by darkening the appropriate bubbles of the 4 × 4 matrix given in the ORS.
Column I [JEE 2007]
(A) simple cubic and face-centred cubic
(B) cubic and rhombohedral
(C) cubic and tetragonal
(D) hexagonal and monoclinic
(P) have these cell parameters a = b = c and a = b = g
(Q) are two crystal systems
(R) have only two crystallographic angles of 90°
(S) belong to same crystal system.
Ans. (A) P, S
(B) P, Q
(D) Q, R
Q 2. The edge length of unit cell of a metal having atomic weight 75 g/mol is 5Å which crystallizes in cubic lattice. If the density is 2 g/cc then find the radius of metal atom. (NA = 6 × 1023). Give the answer in pm. [JEE 2006]
Ans. 216.5 pm
Q 3. An element crystallises in FCC lattice having edge length 400 pm. Calculate the maximum diameter which can be placed in interstital sites without disturbing the structure. [JEE 2005]
Ans. 117.1 pm
Q 4. (i) AB crystallizes in a rock salt structure with A : B = 1 : 1. The shortest distance between A and B is Y1/3 nm. The formula mass of AB is 6.023 Y amu where Y is any arbitrary constant. Find the density in kg m_3.
(ii) If measured density is 20 kg m-3. Identify the type of point defect. [JEE 2004]
(i) = 5 kg m-3
(ii) There is huge difference in theoretically calculated density and observed density. It is only possible if some foreign species occupies interstitial space i.e., substitution defect.
Q 5. Marbles of diameter 10 mm each are to be arranged on a flat surface so that their centres lie within the area enclosed by four lines of length each 40 mm. Sketch the arrangement that will give the maximum number of marbles per unit area, that can be enclosed in this manner and deduce the expression to calculate it. [JEE 2003]
Q 6. In any ionic solid [MX] with schottky defects, the number of positive and negative ions are same. [T/F] [JEE - 2000]
Q 7. A metal cryatallises into two cubic phases, FCC and BCC whose unit cell lengths are 3.5 and 3.0 Å respectively. Calculate the ratio of densities of FCC and BCC. [JEE - 1999]
Q 8. The number of hexagonal faces that are present in a truncated octahedron is [JEE - 2011]