Every Book Back multiple-choice question from Solid State (12th Standard Chemistry, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Graphite and diamond are
- A. covalent and molecular crystals
- B. ionic and covalent crystals
- C. both are covalent network crystalsCorrect
- D. ionic and molecular crystals
Explanation. Both graphite and diamond are examples of covalent solids where the constituent atoms are linked together entirely by covalent bonds in a three-dimensional network.
Q2
Anisotropy is exhibited by
- A. Glass
- B. Barium chlorideCorrect
- C. Wood
- D. Paper
Explanation. Crystalline solids like barium chloride are anisotropic, meaning their physical properties show different values when measured along different directions within the crystal.
Q3
The ratio of number of close packed atoms to tetrahedral holes in a cubic close packing is
- A. 1:1
- B. 1:2Correct
- C. 2:1
- D. 1:4
Explanation. In any close-packed arrangement, if the number of spheres is \(n\), then the number of tetrahedral voids generated is \(2n\), resulting in a ratio of \(1:2\).
Q4
Solid \(CO_2\) is an example of
- A. Covalent solid
- B. metallic solid
- C. molecular solidCorrect
- D. ionic solid
Explanation. Solid carbon dioxide consists of discrete molecules held together by weak intermolecular forces, which characterizes it as a molecular solid.
Q5
Assertion : monoclinic sulphur is an example of monoclinic crystal system
Reason: for a monoclinic system, \(a \neq b \neq c\) and \(\alpha = \gamma = 90^{\circ}\), \(\beta \neq 90^{\circ}\)
- A. Both assertion and reason are true and reason is the correct explanation of assertion.Correct
- B. Both assertion and reason are true but reason is not the correct explanation of assertion.
- C. Assertion is true but reason is false.
- D. Both assertion and reason are false.
Explanation. Monoclinic sulphur belongs to the monoclinic crystal system, which is defined by three unequal axes and angles where two are ninety degrees and the third is different.
Q6
In calcium fluoride, having the fluorite structure the coordination number of \(Ca^{2+}\) ion and \(F^{-}\) Ion are
- A. 4 and 2
- B. 6 and 6
- C. 8 and 4Correct
- D. 4 and 8
Explanation. In the fluorite crystal lattice, each calcium cation is coordinated by eight fluoride anions, while each fluoride anion is surrounded by four calcium cations.
Q7
The number of unit cells in 8 gm of an element X ( atomic mass 40) which crystallizes in bcc pattern is (\(N_A\) is the Avogadro number)
- A. \(6.023 \times 10^{23}\)
- B. \(6.023 \times 10^{22}\)Correct
- C. \(60.23 \times 10^{23}\)
- D. \(6.023 \times 10^{23} \times \left( \frac{8}{40} \right)\)
Explanation. 8 grams of an element with atomic mass 40 corresponds to 0.2 moles. Since a BCC unit cell contains two atoms, the number of unit cells is \(0.1 N_A\).
Q8
In a solid atom M occupies ccp lattice and \(\frac{1}{3}\) of tetrahedral voids are occupied by atom N. find the formula of solid formed by M and N.
- A. MN
- B. \(M_3N\)
- C. \(MN_3\)
- D. \(M_3N_2\)Correct
Explanation. In CCP, there are 4 M atoms and 8 tetrahedral voids. Filling one-third of the voids gives 8/3 N atoms. The ratio \(M:N\) is \(4:8/3\), which simplifies to \(M_3N_2\).
Q9
The ionic radii of \(A^{+}\) and \(B^{-}\) are \(0.98 \times 10^{-10}\) m and \(1.81 \times 10^{-10}\) m. the coordination number of each ion in AB is
- A. 8
- B. 2
- C. 6Correct
- D. 4
Explanation. The radius ratio \(r^{+}/r^{-}\) is \(0.541\). Since this value lies between \(0.414\) and \(0.732\), the ions adopt an octahedral arrangement with a coordination number of 6.
Q10
CsCl has bcc arrangement, its unit cell edge length is 400pm, its inter atomic distance is
- A. 400pm
- B. 800pm
- C. \(\sqrt{3} \times 100\) pm
- D. \(\left( \frac{\sqrt{3}}{2} \right) \times 400\) pmCorrect
Explanation. In a body-centered cubic lattice, the shortest distance between the centers of two atoms is half the length of the body diagonal, which is \((\sqrt{3}a)/2\).
Q11
A solid compound XY has NaCl structure. if the radius of the cation is 100pm, the radius of the anion will be
- A. \(\frac{100}{0.414}\)Correct
- B. \(\frac{0.732}{100}\)
- C. \(100 \times 0.414\)
- D. \(\frac{0.414}{100}\)
Explanation. In an sodium chloride crystal structure, the ratio of the radius of the cation to the anion corresponds to an octahedral void value of zero point four one four. Thus, the anion radius is the cation radius divided by this ratio.
Q12
The vacant space in bcc lattice unit cell is
- A. 48%
- B. 23%
- C. 32%Correct
- D. 26%
Explanation. The packing efficiency of a body-centered cubic unit cell is sixty-eight percent. Consequently, the empty or vacant space within the lattice is calculated by subtracting the occupied volume from the total volume, resulting in thirty-two percent.
Q13
The radius of an atom is 300pm, if it crystallizes in a face centered cubic lattice, the length of the edge of the unit cell is
- A. 488.5pm
- B. 848.5pmCorrect
- C. 884.5pm
- D. 484.5pm
Explanation. In a face-centered cubic lattice, the relationship between edge length and atomic radius is defined by a constant factor related to the face diagonal. Applying this geometry to the given radius yields a value of approximately eight hundred forty-eight point five.
Q14
The fraction of total volume occupied by the atoms in a simple cubic is
- A. \(\frac{\pi}{4\sqrt{2}}\)
- B. \(\frac{\pi}{6}\)Correct
- C. \(\frac{\pi}{4}\)
- D. \(\frac{\pi}{3\sqrt{2}}\)
Explanation. The packing fraction for a simple cubic structure is determined by calculating the ratio of the volume of one atom to the total volume of the cube, which simplifies to pi divided by six.
Q15
The yellow colour in NaCl crystal is due to
- A. excitation of electrons in F centersCorrect
- B. reflection of light from Cl- ion on the surface
- C. refraction of light from Na+ ion
- D. all of the above
Explanation. The appearance of color in sodium chloride is caused by anionic vacancies trapped by electrons, known as F-centers. These electrons absorb specific wavelengths of light, leading to electronic transitions that produce the observed yellow hue.
Q16
If ‘a’ stands for the edge length of the cubic system; sc, bcc, and fcc. Then the ratio of radii of spheres in these systems will be respectively.
- A. \(\frac{1}{2}a : \frac{\sqrt{3}}{2}a : \frac{\sqrt{2}}{2}a\)
- B. \(\frac{1}{2}a : \sqrt{3}a : \frac{1}{2}a\)
- C. \(\frac{1}{2}a : \frac{\sqrt{3}}{4}a : \frac{1}{2\sqrt{2}}a\)Correct
- D. \(\frac{1}{2}a : \frac{\sqrt{3}}{2}a : \frac{1}{2}a\)
Explanation. The atomic radius for each cubic system is derived from its specific geometry. For simple cubic, body-centered, and face-centered structures, the radii are half the edge, one-fourth the body diagonal, and one-fourth the face diagonal, respectively.
Q17
If ‘a’ is the length of the side of the cube, the distance between the body centered atom and one corner atom in the cube will be
- A. \(\frac{2}{3}a\)
- B. \(\frac{4}{3}a\)
- C. \(\frac{\sqrt{3}}{4}a\)
- D. \(\frac{\sqrt{3}}{2}a\)Correct
Explanation. In a cubic lattice, the body diagonal length is defined as the square root of three times the edge length. The distance from a corner atom to the center atom is exactly half of this diagonal distance.
Q18
Potassium has a bcc structure with nearest neighbor distance 4.52 \(\text{\AA}\). its atomic weight is 39. its density will be
- A. \(915 \text{ kg m}^{-3}\)Correct
- B. \(2142 \text{ kg m}^{-3}\)
- C. \(452 \text{ kg m}^{-3}\)
- D. \(390 \text{ kg m}^{-3}\)
Explanation. Density is calculated by relating the number of atoms in a body-centered cubic unit cell, the atomic mass, and the cell volume. The cell edge is derived from the nearest neighbor distance to complete the calculation.
Q19
Schottky defect in a crystal is observed when
- A. unequal number of anions and cations are missing from the lattice
- B. equal number of cations and anions are missing from the latticeCorrect
- C. an ion leaves its normal site and occupies an interstitial site
- D. no ion is missing from its lattice.
Explanation. A Schottky defect is a point defect in ionic solids that occurs when an equal number of positive and negative ions are missing from their lattice sites, maintaining the crystal's overall electrical neutrality.
Q20
The cation leaves its normal position in the crystal and moves to some interstitial position, the defect in the crystal is known as
- A. Schottky defect
- B. F center
- C. Frenkel defectCorrect
- D. non-stoichiometric defect
Explanation. A Frenkel defect occurs when an ion, typically the smaller cation, is displaced from its regular lattice site and occupies an internal interstitial position within the structure, keeping the mass and density constant.
Q21
Assertion: due to Frenkel defect, density of the crystalline solid decreases.
Reason: in Frenkel defect cation and anion leaves the crystal.
- A. Both assertion and reason are true and reason is the correct explanation of assertion.
- B. Both assertion and reason are true but reason is not the correct explanation of assertion.
- C. Assertion is true but reason is false.
- D. Both assertion and reason are falseCorrect
Explanation. In a Frenkel defect, ions move to interstitial positions inside the lattice rather than leaving it entirely. Since the total mass and volume of the crystal remain unchanged, the density does not decrease, making both statements false.
Q22
The crystal with a metal deficiency defect is
- A. NaCl
- B. FeOCorrect
- C. ZnO
- D. KCl
Explanation. Metal deficiency defects are common in transition metal compounds like iron(II) oxide. These arise when metal ions are missing from the lattice, and neighboring metal ions adopt a higher oxidation state to maintain charge balance.
