solid state 12th cet mc

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MHT-CET 2015
Q1. Select a ferromagnetic material from the following.
(A) Dioxygen
(B) Chromium(IV) oxide
(C) Benzene
(D) Dihydrogen monoxide
Correct Answer
(B) Chromium(IV) oxide
Detailed Explanation:
  • Ferromagnetism: Substances that show permanent magnetism even when the external magnetic field is removed. This occurs due to the spontaneous alignment of magnetic moments (domains) in the same direction.
  • While metals like Iron (Fe), Cobalt (Co), and Nickel (Ni) are classic examples, Chromium(IV) oxide (CrO2) is a unique metallic oxide.
  • Because of its strong ferromagnetic properties, it was historically the standard material used in high-fidelity magnetic recording tapes (cassettes).
MHT-CET 2016
Q2. Which among the following solids is a non-polar solid?
(A) Hydrogen chloride
(B) Sulphur dioxide
(C) Water
(D) Carbon dioxide
Correct Answer
(D) Carbon dioxide
Detailed Explanation:
  • A non-polar solid is composed of molecules where the net dipole moment (μ) is zero.
  • In HCl, SO2, and H2O, there is an electronegativity difference and asymmetrical geometry, leading to a permanent dipole (μ ≠ 0).
  • CO2 has a linear geometry (O=C=O). Although the C=O bonds are polar, the two bond dipoles point in exactly opposite directions and cancel each other out perfectly (μ = 0).
  • Therefore, in its solid state (Dry Ice), it forms a non-polar molecular crystal.
MHT-CET 2016
Q3. Which metal crystallizes in a simple cubic structure?
(A) Polonium
(B) Copper
(C) Nickel
(D) Iron
Correct Answer
(A) Polonium
Detailed Explanation:
  • Simple Cubic (SC) packing is very inefficient, with a packing efficiency of only 52.4%. Because of the large amount of empty space, most metals prefer denser arrangements like BCC or FCC.
  • Polonium (Po) is the only element that crystallizes in a simple cubic lattice under standard conditions.
  • Copper and Nickel typically crystallize in FCC, while Iron (at room temp) crystallizes in BCC.
MHT-CET 2016
Q4. In face-centred cubic unit cell, what is the volume occupied?
(A) (4/3) πr3
(B) (8/3) πr3
(C) (16/3) πr3
(D) (64r3) / (3√3)
Correct Answer
(C) (16/3) πr3
Detailed Explanation:
  1. In a Face-Centred Cubic (FCC) unit cell, the effective number of atoms (Z) is calculated as:
    Atoms at 8 corners: 8 × 1/8 = 1 atom
    Atoms at 6 faces: 6 × 1/2 = 3 atoms
    Total (Z) = 4 atoms.
  2. The volume of a single atom (assuming it is a sphere) is given by the formula: Vsphere = (4/3) πr3.
  3. Total volume occupied = Z × Vsphere
  4. Total volume = 4 × (4/3) πr3 = (16/3) πr3.
MHT-CET 2019
Q5. How many total spheres of constituent particles are present in bcc type of unit cell?
(A) 2
(B) 1
(C) 4
(D) 3
Correct Answer
(A) 2
Detailed Explanation:
  1. A Body-Centred Cubic (BCC) unit cell has particles at all eight corners and one particle at the very center of the cube.
  2. Corner Contribution: Each corner atom is shared by 8 adjacent unit cells. So, 8 corners × (1/8) = 1 atom.
  3. Body Center Contribution: The atom at the center is not shared with any other cell. So, 1 center × 1 = 1 atom.
  4. Total atoms (Z) = 1 (corners) + 1 (center) = 2 atoms.

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