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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 601. |
Assertion (A) : in `CsCl` crystal, `Cs^(o+)` ions asopt bcc arragement. Reason (R ) : For `N` atoms adopting bcc arragement, there are `2N TVs`.A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`C. If `(A)` is correct, but `(R)` is incorrect.D. If both `(A)` is incorrect, but `(R)` is correct. |
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Answer» Correct Answer - C (A) is correct but (R) is wrong. Correct (R): For `N` atoms adopting fcc arrangement, there are `2NTVs`. |
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| 602. |
Metals have conductivity of the order of `(ohm^(-1)M^(-1))`A. `10^(2)-10^(4)`B. `10^(4)-10^(7)`C. `10^(7)-10^(8)`D. `gt10^(8)` |
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Answer» Correct Answer - B Metals have conductivity of the ordre of `10^(4)-10^(7)` oh `m^(-1)m^(-1)` |
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| 603. |
Which substance will conduct the current in the solid state ?A. DiamondB. GraphiteC. iodineD. Sodium chloride |
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Answer» Correct Answer - B Graphite conducts electricity in the solid state. |
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| 604. |
Crystals where dipoles may align themselves in an ordered manner so that there is a net dipole moment, exhibitA. pyro-electricityB. para,agmetosmC. dimagnetismD. antiferro-electricity |
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Answer» Correct Answer - B Crystals having a net dipole moment show paramagnetism. |
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| 605. |
Space lattice of `CaF_(2)` isA. Face centred cubicB. Body centred cubicC. Simple cubicD. Hexagonal closed packing |
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Answer» Correct Answer - a Space lattic of `CaF_(2)` is face centered cubic. |
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| 606. |
Which of the following statement is not true about amorphous solids ?A. On heating they may become crystalline at certain temperature .B. They may become crystalline on keeping for long time.C. Amorphous solids can be moulded by heating .D. They are anisotropic in nature. |
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Answer» Correct Answer - B |
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| 607. |
The edge length of unit cell of a metal having molecular weight `75 g mol^(-1)` is `5 Å` which crystallizes in cubic lattice. If the density is `2 g cc^(-1)`, then find the radius of metal atom `(N_(A) = 6 xx 10^(23))`. Give the answer in pm. |
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Answer» Correct Answer - 216.5 pm (so, the required answer is 217 pm) `rho=(Zxxm)/(N_(A)V)rArrZ=(rhoN_(Aa^(3)))/(m)=(2xx6xx10^(23)xx(5xx10^(-4)))/(75)approx2` (Therefore, metal crystallizes in bcc strucutre and for a bcc lattice `sqrte(3)a=4r`) `r=(sqrt(3)a)/(4)=sqrt(3)/(4)xx5overset(@)A=2165overset(@)A=216.5`pm (so, the required answer is 217pm) |
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| 608. |
Which of the following is an amorphous solid ?A. Graphite ©B. Quartz glass ` (SiO_(2))`C. Chrome alumD. Silicon carbide (SiC) |
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Answer» Correct Answer - D |
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| 609. |
Which of the following in not a charateristic of a crystalline solid ?A. Define and characteristic heat of fusion.B. Isotropic nature.C. A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal.D. A true solid. |
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Answer» Correct Answer - B |
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| 610. |
Twenty precent of the surface sites of a catalyst is occupied by nitrogen molecules. The density of surface sites is `6.023xx10^(14)cm^(-2)` . The total sarface area is `1000cm^(2)` . The catalyst is is henced to `300K` and nitrogen is completely desorbed a pressure of `0.001` atm and volume of `2.46cm^(3)` . Calculate the number of sites occupied by niitrogen molecules. |
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Answer» Correct Answer - 2 `N_(2)=0.001` atm: `T=300K, V=2.46cm^(3)` `therefore` Number of `N_(2)` molecules `=(PV)/(RT)xxN_(0)=(0.001xx2.46xx10^(-3))/(0.082xx300)xx6.023xx10^(23)=6.016xx10^(16)` Now, total number of surface sites =DensityxxxTotal surface area =`6.023xx10^(14)xx1000=6.023xx10^(17)` Site occupied by `N_(2)` molecules `=(20)/(100)xx6.023xx10^(!7)=12.04xx10^(!6)` `therefore` Number of stites occupied by each `N_(2)` molecule `=(12.04xx10^(16))/(6.016xx10^(16))=2` |
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| 611. |
How many nearest neighbours surrounded each particle in a face-centred cubic lattice?A. 4B. 6C. 8D. 12 |
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Answer» Correct Answer - D For fcc, CN = 1.2. |
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| 612. |
Which of the following dimensio of a unit cell represent a cubic unitA. `a = b = c , alpha = beta =gamma = 90^(@)`B. `a = b = c , alpha = beta = 90^(@) ne gamma`C. `a = b ne c , alpha = gamma = 90^(@)`D. `a ne b ne c , alpha ne beta ne gamma` |
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Answer» Correct Answer - A For SCC, a = b = c and `alpha = beta = gamma = 90^(@)` |
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| 613. |
A crystalline solidA. Changes abruptly from solid to liquid when heatedB. Has no definete melting pointC. Undergoes deformation of its geometry easityD. Has an irregular J- dimensional arrangements |
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Answer» Correct Answer - a In crystalline solid there is perfact arrangement of the consitent particles only at ` 0 K` .As the temperature increases the chance that a lattics sine may be unocopiod by an lon increases .As the number of defocts increases with temperature solid changes to liquid |
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| 614. |
Amorphous solid areA. Supercooled liquidB. Liquid in real senseC. Solid substance in real, senseD. Substance with definete melting point |
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Answer» Correct Answer - a Amorphous solids have ordered arrangement (i.e. no definite shape) nor have shape melting point like crystals but when heater ,they becomes pliable untill they assume the properies usually related to liquid it is therefore they are regarded as supercoled liquids. |
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| 615. |
Which of the following statement is//are correct?A. Piezoelectric crystals are used as pick-ups in record players, they are also used in microphones, ultrasonic generators, and sonar detectors.B. `BaTiO_(3)`, Rochelle salt, `KH_(2)PO_(4)`, and quartz are ferroelectric and piezoelectric solids.C. The temperature above which no ferromagnetism is observed is called curie termperature.D. The temperature at which the material shows super-conductivity is called transition termperature. |
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Answer» Correct Answer - A::B::C::D (a, b, c, d) All fectual statements. |
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| 616. |
Which of the following statement is//are correct?A. A diode is a combination of `p`-and `n`-type semiconductors which is used as a rectifier.B. Transistors are sandwich semiconductors of the type `pnp` or `npn` which are used to detect or amplify radio or audio signals.C. Monoxides of transition metals, all of which posses `NaCl` structures, show very large variations in electrical properties.D. `ReO_(3)` has the conductivity as well as appearance like that of copper. |
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Answer» Correct Answer - A::B::C::D (a, b, c, d) All fectual statements. |
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| 617. |
Which of the following statement is//are correct?A. All ferroelectric solids are piezoelectric.B. All piezoelectric solids are ferroelectric.C. Lead zirconate `(PbZ_(r)O_(3))` is a an antiferroelectric is an antiferroelectric crystal.D. `BaTiO_(3)`, (barium titanate) is a ferroelectric crystal. |
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Answer» Correct Answer - A::C::D (a, c, d) All fectual statements. |
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| 618. |
Due of Frenkel defectA. Density of the crystal increasesB. Conducation and increasesC. Conduction decreasesD. Crystal becomes charged electrically |
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Answer» Correct Answer - B Conduction increases due to the movement of ion in one direction and movement of hole on the other direction on applying electric field. |
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| 619. |
Amorphous solids are classified asA. Isotropic and supercooled liquidsB. Anisotropic and supercolled liquidsC. Isoenthalpic and supercooled liquidsD. Isotropic and supercooled solids |
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Answer» Correct Answer - A Fractual statement. |
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| 620. |
Which of the following is used to convert sunlight into electricity?A. Amorphous sulphurB. Amorphous phosphorusC. Amorphous siliconD. Both (1) and (2) |
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Answer» Correct Answer - 3 Amorphous solids find may applications because of their unique properties,In organic glasses are used in construction ,houseware ,laboratory ware,etc. |
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| 621. |
Amorphorous solids such as glass may be classified asA. supercooled liquidsB. supercooled solidsC. superheated liquidD. superheated solids |
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Answer» Correct Answer - 1 A glass is an amorphous solid obtained by cooling a liquid rapidly enough that its basic units are `"frozen"` in random positions before they can assume an ordreed crystalline arrangement Glass is sometimes called as pseduo solid or supercooled liquid because like a liquid it shows a tendency to flow though very slowly. |
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| 622. |
Because of antisotropyA. mica cleaves into long rod like piece and asbestos cleaves into thin sheetsB. mica cleaves into thin sheets and asbestos cleaves into long rod like pieces.C. both mica and asbestos cleave into thin sheetsD. both mica and asbestos cleaves into long rod like pieces |
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Answer» Correct Answer - 2 This is because mica and asbestos are crystalline solids. Asbestos is a variety of fibrous silicate minerals mainly calcium magnesium and for fire proof fabrics.it is used as a heat insulating material and for fire -proof fabris. In halation of the fibres can be extremely dangerous. Mica corroesponds to a group of minerals,the most important of which are muscovite `H_(2)KAl_(3)(SiO_(4))_(3)` and phlogopite,`H_(2)KMgAl(SiO_(4))_(3)`.Naturally occuring mica can be split along its cleavages into small thick pieces (blocks) or thin sheets (spliting). Being a excellent insulator and being resistant to high temperatures, mica is used as a dielectric in capacitors, as a support for electrodes in thermonic valves,and for heating elements in irons ,etc As mica is also transparent it is used for inspection windows of furnance. Isotropic solids have the same mechanical strength electrical strength optical strength in all directions. |
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| 623. |
Which of the following is not a molecular crystal?A. IodineB. SiliconC. PhosphorusD. Sulphur |
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Answer» Correct Answer - 2 In a molecular crystal,the lattice points are occupoed by moleucles and the attractive foces between them are van der Waals and/or hydrogen bonding. The simplest molecular solids are the frozen noble gases,e.g solid neon. In this case the molecules are single atoms and the intermolecular interactions are London forces. These forces are nondirectional ( in constract to covalent bonding, which is directional) ,and the maximal attraction is obtained when each atoms is surreounded by the largest possible number of other atoms. Another Example of a molecular crystal is solid sulphur dioxide `(SO_(2))` in which the predominant attractive froce is dipole-dipole interaction, Intermolecular hydrogen bonding is mainly responsible for maintaining the three dimensional ice lattice. Other Examples of molecular crystals are iodine `(I_(2))`, phosphorous `(P_(4))`, and sulphur`(S_(8))` Because van der Waals forces and hydrogen bonding are generally quite weak compared with the covalent and ionic bonds, molecular crystals are more easily broekn apart than ionic and crystals indeed most molecular crystals melt below `100^(@)` Silion germanium and grey tin (a nonmetallic allotrope) are covalent crystals and have "Diamond " structure. |
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| 624. |
Which of the following is a molecular crystal?A. iceB. NaCIC. GraphiteD. SiC |
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Answer» Correct Answer - a ice is a molecular crystan in which the consthant units are molecules and the interparticle force are hydrogen bonds. |
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| 625. |
Tellurium forms oxides of the formula `TeO, TeO_(2) and TeO_(3)`. What is the nature of these tellurium oxides ?A. Monoclinic systemB. Tetragonal systemC. Rhombic systemD. Triclinic system |
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Answer» Correct Answer - B `TeO_(2)` belongs to tetragonal system. |
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| 626. |
A metal crystallizes into two cubic phases, face-centred cubic and body-centred cubic, which have unit cell lengths `3.5` and `3.0 A`, respectively. Calculate the ration of densities of fcc and bcc.A. 2B. 1.26C. 3.34D. 1.8 |
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Answer» Correct Answer - 2 `(rho_(1))/(rho_(2))=(z_(1))/(z_(2)).((a_(2))^(3))/((a_(1))^(3))` |
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| 627. |
Cesium atoms are the largest neturally occurring atoms. The radius of `Cs` atom is `2.6 Å`. The number of moles of `Cs` atoms to be laid side by side to give a row of `Cs` atoms `2.5 cm` long is `x xx 10^(-17)`. Find the value of `x`. |
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Answer» Correct Answer - 8 Diameter of Cs= `2xx2.6=5.2overset(@)A=5.2xx10^(-8)cm` Number of atoms in 2.50cm row= `(2.50)/(5.2xx10^(-8))=0.48xx10^(8)=4.8xx10^(7)`Cs atoms `therefore` Moles of Cs atoms= `(4.8xx10^(7))/(6xx10^(23))=0.8xx10^(-16)=8xx10^(-17)` `therefore xxx10^(-17)=8xx10^(-17)rArrx=8` |
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| 628. |
The `"OLIVINE"` series of minerals consists of crystal in which `Fe^(2+)` and `Mg^(2+)` ions may substitute for each other causing susbstitutional impurity defects without changing the volume of unit cell. In `"OLIVINE"` series of minerals, `O^(2-)` ions exist as fcc with `Si^(4+)` occupying one-fourth of `OVs` and divalent metal ions occupying one-fourth of `OVs` and divalent metal ions occupying one-fourth of `TVs`. The density of "forsterite" (magnesium silicate) is `3.21 g cm^(-3)` land that of "fayalite" (ferrous silicate) is `4.34 g cm^(-3)`. The formula of "fayalite mineral" isA. `Fe_(2)SiO_(4)`B. `FeSiO_(4)`C. `Fe_(2)SiO_(6)`D. `Fe_SiO_(3)` |
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Answer» Correct Answer - A For fcc, Number of `O^(2-)` ion=`8 ("corner") xx (1)/(8) "per corner share"` ltbr. `+ 6 ("faces") xx (1)/(2) "per face share"` `= 4` Number of `Si^(4+)` ions `= 1/4 xx "OV" = 1/4 xx 4 = 1//"unit cell"` Number of `Fe^(2+)` ions `= 1/4 xx "TV" = 1/4 xx 8 = 2//"unit cell"` So, formula of `"FAYLITE"` is `overset(+2xx2)(Fe_(2))Si^(4+)O_(4^(2-))` `rArr Fe_(2)SiO_(4)` |
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| 629. |
What is electrical conductivity due to in (a) metals,(b) ionic solids, and © semiconductors ? |
| Answer» (a) Due to flow of electrons. (b) Due to flow of ions in solution or melt and defects in the solid state. (c ) Due to the presence of impurities and defects. | |
| 630. |
The sharp melting point of crystalline solids compared to amorphous solids is due toA. a regular arrangement of consituent particles observed over a short distance in the crystal lattice.B. a regular arrangmenet of constituent particles observed over a long distance in the crystal latticeC. same arrangement of constituent particles in different directions.D. |
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Answer» Correct Answer - B A solid is said to be crystalline if the various constituent structural units (atoms, ions or molecuels) of which the solid is made, are arranged in a definite gerometrical pattern within the solid. The type of forces in crystalline solids are of long range order due to which they have sharp melting point. |
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| 631. |
In CsCl stricture, the coordination number of `Cs^(+)` isA. Equal of that of `Cl^(-)` , that is 6B. Equla to that of `Cl^(-)` , that is 8C. Not equla to that of `Cl^(-)` , that is 6D. Not equla to that of `Cl^(-)` , that is 8 |
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Answer» Correct Answer - B Radius ratio range `0.732-1.00` signifies co-ordination number 8 . In CsCl, co-ordination number ratio is 8 : 8. |
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| 632. |
For cubic - coordination the value of ratio isA. `0.000-0.225`B. `0.225-0.414`C. `0.414-0.732`D. `0.732-1.000 |
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Answer» Correct Answer - D For body centred cubic arrangement coordination number is 8 and radius is `0.732 - 1.000` . |
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| 633. |
Give reason : (a) Why is Frenkel defect found in AgCl but not in NaCl ? (b) What is the difference between phosphourus doped and Gallium doped semicoductors ? |
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Answer» (a) Frenkel defect is found in htose ionic compounds in which idifference in the size of cation and anion is large. This is so in case of AgCl but not in case of NaCl. Due to small size of silver cations `( Ag^(+))` they can fit into the interesitial sites but `Na^(+)` ions cannot fit not the interstitial sites. (b) Silicon doped posphorus gives n-type whereas silicon doped with gallium forms p-type semiconductors . |
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| 634. |
Why LiCl acquires pick colour when heated in Li vapours ? |
| Answer» This is beacause on heating electrons are trapped at the anionic at the anionic sites forming F -centes which absord energy from light and radiate pink colour. | |
| 635. |
For an ionic crystal of the formula `AX` and cooradition number `6`, the value of radius ratio will beA. greater than `0.73`B. In between `0.41 and 0.22`C. in between `0.73 and 0.41`D. Less than `0.22` |
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Answer» Correct Answer - c The srtructure arrangement of coordanation number `6` is octabedral and the radius ratio is `0.414 - 0.732` .The example of octabedral is `KCI` and `NaCI`. |
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| 636. |
An example of a non- stoichiometric compound isA. `Al_(2)O_(3)`B. `Fe_(3)O_(4)`C. `NiO_(2)`D. PbO |
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Answer» Correct Answer - B `Fe_(3)O_(4)` is a non-stoichiometric compound because in it the ratio of the cations to the anions becomes different from that indicated by the chemical formula. |
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| 637. |
An element with molar mass `2.7 xx 10^(-2) kg mol^(-1)` forms a cubic unit cell with edge length 405 pm . If its density is `2.7 xx 10^(3) kg m^(-3)` what is the nature of the cubic unit cell ? |
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Answer» Density (d) = `(Z xx M)/(a^(3) xx N_(A)) so , Z = ( d xx a^(3) xx N_(A))/(M)` Given , M = `2.7 xx 10^(-2) kg mol^(-1)` `a = 405 ` pm = `405 xx 10^(-12) m = 4.05 xx 10^(-10)` m `d = 2.7 xx 10^(3) kgm^(-3)` `N_(A) = 6.022 xx 10^(23) mol^(-1)` . `Z = ((2.7 xx 10^(3) kg m^(-3)) (4.05 xx 10^(-10) m)^(3) xx (6.022 xx 10^(23) mol^(-1)))/((2.7 xx 10^(-2) kg mol^(-1)))` `=3.99 = 4 ` Since , there are four atoms per unit cell , the cubic unit cell must be face - centred. |
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| 638. |
An element with molar mass 27 g ` mol^(-1)` forms a cubic unit cell with edge length ` 4.05 xx 10^(-8)` cm. If its density is ` 2.7 " g cm^(-3) ` , what is the nature of the cubic unit cell ? |
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Answer» Correct Answer - BCC `p = ( Z xx M)/(a^(3)xx N_(A)) or Z = (pxx a^(3) xx N_(A))/M = (( 2.7 " g cm"^(-3)) (4.05xx10^(-8)"cm")^(3)(6.02xx10^(23)"mol"-1))/( 27 " g mol"^(-1))=4` Hence , it has face -centred cubic unit cell. |
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| 639. |
If `NaCl` is doped with `10^(-3)` mol% of `SrCl_(2)`, what is the concentration of cation vacancies? |
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Answer» Correct Answer - `6.022xx10^(18)` Due to the addition of strontium chloride `(SrCl_(2))`, each `Sr^(2+)` ion replaces two `Na^(+)` ions but occupies only one lattice point in place of `Na^(+)` ion. This leads to one cation vacancy. Number of moles of cation vacancies is 100 mol of NaCl = `10^(-3)` Number of moles of cation vacancies in 1 mol `=(10^(-3))/(100)=10^(-5)mol` Total number of cation vacancies `=10^(-5)xxN_(0)` `=(10^(-5)mol)xx(6.022xx10^(23)mol^(-1)` `=6.022xx10^(18)` |
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| 640. |
If `NaCl` is doped with `10^(-2) mol% SrCl_(2)`, what is the concentration of the cation vacancies? |
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Answer» Doping of `NaCl` with `10^(-2) mol% SrCl_(2)` means that `100` mol of `NaCl` are doped with `10^(-2)` mol of `SrCl_(2)`. `:. 1 mol` of `NaCl` is doped with `SrCl_(2) = (10^(-2))/(100) = 10^(-4) mol` As each `Sr^(2+)` ion introduces one cation vacancy, therefore, the concentration of cation vacancies `= 10^(-4)` mol/mol of `NaCl` `= 10^(-4) xx 6.023 xx 10^(23) mol^(-1)` `= 6.02 xx 10^(19) mol^(-1)` |
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| 641. |
If `NaCl` is doped with `10^(-3) mol% GaCl_(3)`, what is the concentration of the cation vacancies? |
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Answer» `100 mol` of `NaCl` are doped with `10^(-3) mol` of `GaCl_(3)`. `:. 1 mol` of `NaCl` is doped with `GaCl_(3) = (10^(-3))/(100) = 10^(-5) mol` As one `Ga^(3+)` ion is introduced, three `Na^(o+)` have to be removed to maintain the electrical neutrality. So as one vacancyis filled by `Ga^(3+)`, two cation vacancies are formed. `:.` Concentration of cation vacancy `= 2 xx 10^(-5)` mol/mol of `NaCl` `= 2 xx 10^(-5) xx 6.023 xx 10^(23) mol^(-10)` `= 12.046 xx 10^(-18) mol^(-1)` `= 1.2046 xx 10^(-19) mol^(-1)` |
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| 642. |
The total of tetrahedral voids in the face centred unit cell is …………. .A. 6B. 8C. 10D. 12 |
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Answer» Correct Answer - B No. of atoms per unit cell in the face centred cubic unit cell = 4. No. of tetrahedral voids `=4xx2=8` |
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| 643. |
Sodium atom crystallizes in body centered cubic with a=4.29 `overset(@)A`. The radius of sodium atom isA. `18.6 overset(@)A`B. `1.86overset(@)A`C. `1.86`pmD. 1860pm |
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Answer» Correct Answer - B `4r=sqrt(3)arArr r=(sqrt(3)a)/(4)=(1.732xx4.29)/(4)=1.86overset(@)A` . |
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| 644. |
Cations are present in the interstitial sites in …………… .A. Frenkel defectB. Schottky defectC. Vacancy defectD. Metal deficiency defect. |
| Answer» Correct Answer - A | |
| 645. |
Schottky defect.A. thereisno effect on the densityB. density of the crystal increasesC. density of the crystal decreasesD. any of the above three can happen. |
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Answer» Correct Answer - C As a result of Schottky defect, the density of the crystal decreases. |
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| 646. |
Which compound will show the highest lattice energy ?A. KfB. NaFC. CsFD. RbF |
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Answer» Correct Answer - B `Na^(+)` being smallest in size, the ionic bond in NaF will be strongest. |
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| 647. |
Silicon is aA. ConductorB. SemiconductorC. Non conductorD. Metal complex |
| Answer» Correct Answer - 2 | |
| 648. |
Schottky defect is observed in crystals when ……………. .A. some cations move from their lattice site to interstitial sitesB. equal number of cations and anions are missing from the lattice.C. some lattice sites are occupied by electronsD. some impurity is present in the lattice. |
| Answer» Correct Answer - B | |
| 649. |
Non-stoichionmetric metal deficiency is shown in the salts of :A. all metalsB. alkali metals onlyC. alkaline earth metals onlyD. Transition metals only . |
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Answer» Correct Answer - D Metal deficiency defect is shown by transition metals because they possess variable valency. |
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| 650. |
Explain paramagnetism with suitable example . |
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Answer» Paramagnetic Substances : If the magnetic lines of forces are drawn into the substance the field (B) in the substances is greater than the applied(H) i.e. , `B gt H` . Such a substance is called paramagnetic substance . Paramagnetic substance moves from a weaker part of the field to a stronger part of the field . Paramagnetic substances are weakly attracted in a external Magnetic field . They exhibit paramagnetism due to the presence of unpaired electrons . E.g. : `Cr^(+3) , Sc^(+2) , K_(3) [Fe(CN)_(6)]` . |
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