Assertion Reason Questions Solid State
In the following questions, two statements Assertion and Reason are given. Mark
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.
(e) Assertion and Reason both are false.
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Que 1. Assertion: For fluorite structure, the F– ions occupy tetrahedral void, but Ca+2 ions occupy c.c.p.
Reason: The radius ratio of fluorite structure is 0.225.
Ans 1. (c) Assertion is true but Reason is false.
Explanation: In flourite structure, the F− ions occupy tetrahedral voids and Ca2+ ions form cubic closed packing. Each Ca2+ is surrounded by 8F− ions and it has a coordination number of 8 whereas each F− ion is surrounded by 4 Ca2+ ions and it has a coordination number of 4. Thus, this structure has 8:4 coordination. The radius ratio of fluorite structure is usually more than 0.732.
Que 2. Assertion: Diamond is a precious stone.
Reason: Carbon atoms are tetrahedrally arranged in diamonds.
Ans 2. (b) Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
Explanation: It is true that in the diamond structure, carbon atoms are arranged tetrahedrally (sp3 hybridized) but it is not the correct explanation of assertion.
Que 3. Assertion: The total number of atoms present in a simple cubic unit cell is one.
Reason: Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.
Ans 3. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Explanation: In a simple cubic unit cell, only corners are occupied by atoms. Thus, the total number of atoms present in the unit cell will be one. 8 × 1/8 = 1.
Assertion Reason Questions Solid State
Que 4. Assertion: Graphite is a good conductor of electricity however diamond belongs to the category of insulators.
Reason: Graphite is soft in nature on the other hand diamond is very hard and brittle.
Ans 4. (b) Assertion and reason both are correct statements but the reason is not the correct explanation for assertion.
Explanation: The correct explanation for reason is, In graphite, carbon atoms are arranged in different layers and each atom is covalently bonded to three of its neighboring atoms in the same layer. The fourth electron is free to move which makes graphite a good conductor.
Que 5. Assertion: Electrical conductivity of semiconductors increases with increasing temperature.
Reason: With the increase in temperature, a large number of electrons from the valence band can jump to the conduction band.
Ans 5. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Explanation: The electrical conductivity of solids is due to the motion of electrons and holes or ions.
Conduction of ionic solids is due to the absence of vacancies and other defects. Thus, the conductivity of semiconductors, as well as insulators, is mainly because of impurities and defects present in them. Electrons and holes produced by the ionization of defects contribute to conduction in these solids.
The electrical conductivity of semiconductors increases with increasing temperature because, with an increase in temperature, the number of electrons from the valence bond can jump to the conduction band in semiconductors.
Que 6. Assertion: In the crystal lattice, the size of the cation is larger in a tetrahedral hole than in an octahedral hole.
Reason: The cations occupy more space than anions in crystal packing.
Ans 6. (d) Assertion is false but Reason is true.
Explanation: Tetrahedral holes are smaller in size than octahedral holes. Cations usually occupy less space than anions.
Que 7. Assertion: Total number of octahedral voids present in the unit cell of cubic close packing including the one that is present at the body center, is four.
Reason: Besides the body center there is one octahedral void present at the center of each of the six faces of the unit cell and each of which is shared between two adjacent unit cells.
Ans 7. (c) Assertion is true but Reason is false.
Explanation: The correct statement for reason is,
Besides the body Centre there is one octahedral void at the Centre of each12 edges which is shared between four adjacent unit cells.”
Octahedral voids present at the body Centre of the cube = 1
12 octahedral voids located at each edge and shared between four unit cells = ( 12 × 1/4 ) = 3
Total number of octahedral voids = 4.
Assertion Reason Questions Solid State
Que 8. Assertion: In any ionic solid (MX) with Schottky defects, the number of positive and negative ions is the same.
Reason: Equal number of cation and anion vacancies are present.
Ans 8. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Explanation: Schottky defect is due to the missing of an equal number of cations and anions.
Que 9. Assertion: In close packing of spheres, a tetrahedral void is surrounded by four spheres whereas an octahedral void is surrounded by six spheres.
Reason: A tetrahedral void has a tetrahedral shape whereas an octahedral void has an octahedral shape.
Ans 9. (c) Assertion is true but Reason is false.
Explanation: Tetrahedral void is so-called because it is surrounded by four spheres tetrahedrally while octahedral void is so-called because it is surrounded by six spheres octahedrally.
Que 10. Assertion: The packing efficiency is maximum for the fcc structure.
Reason: The coordination number is 12 in fcc structures.
Ans 10. (b) Assertion and reason both are correct statements but the reason is not correct explanation for assertion.
Explanation: The correct explanation is
In fcc structure no. of atoms present = 4 per unit cell which provides a maximum packing efficiency of 74%.
Que 11. Assertion: NaCl crystal is sometimes yellow in colour.
Reason: Na+ in the crystal absorbs electrons from the air and hence gives yellow colour.
Ans 11. (c) The assertion is true but Reason is false.
Explanation: NaCl crystal is sometimes yellow in colour due to an excess of sodium.
In NaCl crystal, some chloride ions are missing forming holes. These holes are occupied by electrons to maintain electrical neutrality. The holes occupied by electrons are called F-centres and are responsible for the colour of the compound.
Hence, the Assertion is correct but the Reason is incorrect.
Assertion Reason Questions Solid State
Que 12. Assertion: Anion vacancies in alkali halides are produced by heating the alkali halide crystals with alkali metal vapour.
Reason: Electrons trapped in anion vacancies are referred to as F-centers.
Ans 12. (b) Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
Explanation: On heating, the metal atoms deposit on the surface and finally they diffuse into the crystal and after ionisation the alkali metal ion occupies cationic vacancy whereas electron occupies anionic vacancy.
Que 13. Assertion: Group-13 doped crystals of silicon are called p-type semiconductors.
Reason: Holes (Positive in charge) appear to be responsible for the semiconducting properties.
Ans 13. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Explanation: The addition of a small amount of foreign impurity in the host crystal is called doping. It results in an increase in the electrical conductivity of the crystal. Doping of group 14 elements (such as Si, Ge, etc.) with elements of group 15 (such as As) produces an excess of electrons in the crystals, thus, giving n-type semiconductors. Doping of group 14 elements with group 13 elements (such as Indium) produces holes (electron deficiency) in the crystals. Thus, p-type semiconductors are produced. The symbol ‘p’ indicates the flow of the positive charge. Positive holes are responsible for semiconducting properties like conduction.
Que 14. Assertion: On heating ferromagnetic or ferrimagnetic substances, they become paramagnetic.
Reason: The electrons change their spin on heating.
Ans 14. (b) Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
Explanation: All magnetically ordered solids (ferromagnetic and antiferromagnetic solids) transform to the paramagnetic state at high temperature due to the randomization of spins.
Que 15. Assertion: Lead zirconate is a piezoelectric crystal.
Reason: Lead zirconate crystals have no dipole moment.
Ans 15. (c) The assertion is true but Reason is false.
Explanation: In piezoelectric crystals, the dipoles may align themselves in an ordered manner such that there is a net dipole moment in the crystal.
Assertion Reason Questions Solid State
