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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.
| 501. |
What are the coordination number of `Zn^(2+)` and `S^(2-)` ions in ZnS? |
| Answer» C.N of `Zn^(2+)` = 4, `S^(2-)` = 4. | |
| 502. |
Name the three of crystalline solids having the formula AB. |
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Answer» (i) Zinc blends (ZnS type ) (ii) Rock salt (NaCl type) (iii) Cesium chloride (CsCl type) |
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| 503. |
If x = radius of `Na^(+) " & " y =` radius of `Cl^(-)` & a is the unit cell edge length for NaCl crystal, then which of the given relation is correct ?A. `x + y = a`B. `2x + 2y = a`C. `x + y = 2a`D. `x + y = sqrt2a` |
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Answer» Correct Answer - B `{:(2(r^(+) + r^(-)) = a,"or",r^(+) = x = " radius of " Na^(+)),(2(x + y) = a,,r^(-) = y = " radius of " Cl^(-)):}` |
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| 504. |
How many octahedral tetrahedral voids are per sphere in a unit cell ? |
| Answer» Tetrahedral voids = 2 | |
| 505. |
Amorphous solids areA. isotropic and supercooled liquidsB. anisotropic and supercooled liquidsC. isoenthalpic and superheated liquidsD. isotropic and superheated solids |
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Answer» Correct Answer - A |
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| 506. |
Which of the following statement is not true about the hexagonal close packing ?A. The coordination number is 12.B. It has 74% packing efficiency .C. Tetrahedral voids of the second layer are covered by the spheres of the third layer.D. In this arrangement spheres of the fourth layer are exactly aligned with those of the first layer. |
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Answer» Correct Answer - A In hexagonal close packing , arrangement is ABAB ….. Types and not ABC ABC ……type. Hence, (d) is not true. |
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| 507. |
How many voids per point are present in cubic close packed structures of spheres ? |
| Answer» Octahedral voids = 1 | |
| 508. |
In 3D close packed structures, for every 100 atoms, it containsA. 50 octahedral voidsB. 100 tetrohedral voidsC. 200 octohedral voidsD. 100 octahedral voids |
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Answer» Correct Answer - D In 3D close packed structure for every 100 atoms it contain 100 octahedral voids |
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| 509. |
Which of the following is ferromagnetic ?A. Calcium metalB. Iron metalC. sodium metalD. Zinc metal |
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Answer» Correct Answer - B |
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| 510. |
An element crytallizes in the cubic lattice and the edge of the unit cell is 430 pm. Calculation the number of atoms in a unit cell. [ Atomic mass of Na = 23.0 amu. Density of sodium = 0.9623 g ` cm^(-3) , N_(A) = 6.023 xx 10^(23) mol^(-1)` |
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Answer» Correct Answer - FCC |
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| 511. |
Graphite is an example of:A. ionic solidB. covalent solidC. metallic solidD. none of these |
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Answer» Correct Answer - B |
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| 512. |
An atomic solid crystalliuzen in a body centre cubic lattice and the inner surface of the atoms at the adjacent corner are separated by `60.3 "pm"` .If the atomic mass of A is 48, then density of the solid , is nearly :A. 2.7 g/accB. 5.07 g/ccC. 3.5 g/ccD. 1.75 g/cc |
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Answer» Correct Answer - D `a-2r=60.3` pm bcc `4r=sqrt(3)a, d=(2xx48)/(N_(0)xx(4.5)^(3)xx10^(-24))=1.75g//u` |
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| 513. |
`{:("Column-I","Column-II"),("Dry ice","Ionic solid"),("Silica","Molecular solid"),("Brass","Network solid"),("Wurtzite","Metallic solid"):}`A. A-q,B-r,C-s,D-pB. A-p,B-q,C-s,D-rC. A-r,B-q,C-s,D-pD. A-p,B-q,C-r,D-s |
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Answer» Correct Answer - 1 (A) Dry ice=Molecular solid (containing `H_(2)O` molecules held together) (B) Silica=Network solid (`SiO_(2)` forming a network through covalent bonds) (C) Brass=Metallic solid (copper+Zinc) (D) Wurzite=Ionic solid `overset(2+2-)((ZnS))` |
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| 514. |
which of the following is a network solid?A. `SO_(2)`(Solid)B. `I_(3)`C. DimondD. `H_(2)O` (s) |
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Answer» Correct Answer - C Iodine is a non-polar molecular solid in which iodine molecuels are held together by London force or dispresion force. This is soft and non-conductor of electricity. Water is a hydrogen bonded molecular solid in which H and O are held together by polar covalent bond and each water molecualr held together by hydrogen bonding. due to non-inoc nature, they are not electrical conductor. |
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| 515. |
1 g of X has atoms arranged in cubic packing so as to give best packing efficiency. The possible arrangement isA. simple cubicB. face centred cubicC. body certred cubicD. hexagonal close packing |
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Answer» Correct Answer - B Packing efficiency of ccp is 74% so it best packing is cubic packing |
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| 516. |
Which of the following is a network solid ?A. `SO_(2)` (Solid)B. `I_(2)`C. DiamondD. `H_(2)O` (Ice) |
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Answer» Correct Answer - C |
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| 517. |
In a lattice of X and Y atoms, If X atoms are present at corners and Y atoms at the body centre & one X atom is removed from a corner from each unit cell, then the formula of the compound will be:A. `X_(7)Y`B. `X_(8)Y_(7)`C. `X_(7)Y_(8)`D. `X_(7)Y_(7)` |
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Answer» Correct Answer - C At corner `= (1)/(8)` (for per atom) `rArr X_(1 - (1)/(8)) Y` (one X atom removed) `rArr X_(7//8)y` `rArr x_(7)y_(8)` |
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| 518. |
Solid which do not show the same physical properties in different directions are called:A. pseudo solidsB. isotropic solidsC. polymorphic solidsD. anisotropic solids |
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Answer» Correct Answer - D |
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| 519. |
which of the following statement is true for ionic solids?A. Ionic solids are soluble in non-polar solventB. Under the electric field cation and anions acquire translatory motion in opposite directionsC. Structural units have strong electrostatic force of arrtractionD. Structural units have dipole-dipole interactions |
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Answer» Correct Answer - C |
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| 520. |
which of the following is a network solid?A. `SO_(2)` (Solid)B. `I_(2)`C. DiamondD. `H_(2)O` (Ice) |
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Answer» Correct Answer - C In diamond, the constituent atoms are held together by strong covalent bonds. It is a giant moleculae. Thus , classified as network solid. Note : `SO_(2),H_(2)O" and "I_(2)` are examples of molecular solids. |
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| 521. |
When NaCl crystal is heated in sodium vapors, then it attains yellow colour. It is due toA. electrons trapped in cation vacanciesB. F-centres, which is electron trapped in anion vacancy created by `Cl^(-)`C. F-centres, which is cation trapped in cation vacancy created by `Na^(+)`D. interstitial defect caused by external impurity |
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Answer» Correct Answer - B When NaCl crystal is heated in sodium vapors, then it attains yellow colour. It is due to F-centres, which is electron trapped in anion vacancy created by `Cl^(-)` |
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| 522. |
The vacant space in B.C.C. unit cell isA. 0.32B. 0.1C. 0.23D. 0.46 |
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Answer» Correct Answer - A Packing efficiency `= (2 xx (4)/(3) pi R^(3))/(((4R)/(sqrt3))^(3)) = (sqrt3pi)/(8) = 68%` Vacent space `= 100 - 68 |
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| 523. |
Which one is called pseudo solid?A. `CaF_(2)`B. GlassC. NaClD. All |
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Answer» Correct Answer - B |
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| 524. |
Which one is called pseudo solid?A. glassB. NaClC. KCID. KCI and NaCl both |
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Answer» Correct Answer - A Glass is pseudo solids. |
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| 525. |
Why are solid rigid?A. Because of large intermolecular forcesB. Because of vibration motionC. Because of large intermolecular spaceD. All of the above |
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Answer» Correct Answer - A In solid state the constituent particles are not free to move. They can only oscillate about their mean positions due to strong attraction forces between the particles. That is why solids have a closely packed arrangementand rigid structure. |
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| 526. |
which of the following is not a characteristic of a crystalline solid ?A. Definite and characteristic heat of fusionB. Isotropic natureC. A regular periodically repeated pattern of arrangemet of constituent particles in the entire crystalD. A true solid |
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Answer» Correct Answer - B Crystalline solids are anisotropic in nature, i.e., have different properties in different directions. |
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| 527. |
Which of the following exists as covalent crystals in the solid state ?A. PhosphorusB. IodineC. SiliconD. Sulphur |
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Answer» Correct Answer - B Silicon has covalent network structure wheraes sulphur ` (S_(8))` , phosphorus `(P_(4))` and iodine `(I_(2))` are molecular solids. |
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| 528. |
What is the coordination number in a square close packed structures in two dimensions?A. 2B. 3C. 4D. 6 |
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Answer» Correct Answer - C Co-ordination no. is four in a square close packed arrangement. |
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| 529. |
Which of the following is an amorphous solid?A. Graphite (C )B. Quartz glass (`SiO_(2)`)C. Chrome alumD. Silicon carbide (SiC) |
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Answer» Correct Answer - B Quartz glass `(Sio_(2))` si an amorphous solid due to its short range order of constituent particles . Note Quartz is a a cryis a crystalline solid whilw quartz glass is an amorphous solid . |
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| 530. |
Which of the following statement about amorphous solids is incorrect ?A. They melt over a range of temperatureB. They are anisotropicC. There is no orderly arrangement of particlesD. They are rigid and incompressible |
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Answer» Correct Answer - D Amorphous solids are isotropic. i.e, physical properties like electrical conductively , refractive index, thermal expansion etc. are identical in all directions. |
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| 531. |
Which of the following statements about amorphous solid is incorrect ?A. They melt over a range of temperatureB. They are anisotropicC. There is no orderly arrangment of particlesD. They are rigid and incompressible |
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Answer» Correct Answer - C Amorphous solids have no orderly arrangement of particles i.e., they are isotropic |
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| 532. |
Why does table salt, NaCl, sometimes appear yellow in colour ? |
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Answer» Correct Answer - Yellow colour of NaCl is due to metal excess defect as some `Cl^(-)` ions ( anions) leave their lattice sites and occupied by unpaired electronws. These sites are called F -centres. These electrons absorb energy from bisible reigon for exictation so that complementary colour is yellow . |
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| 533. |
Which of the following is a covalent crystal?A. BenzeneB. UreaC. Zinc sulphideD. Silicon carbide |
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Answer» Correct Answer - 4 Sillion carbide `(SiC)`,also known as carborundum is a dark crystalline solid in which lattice points are occupied by `Si` and `C` atoms held together by strong covalent bonds.It is nearly as hard as diamond used as an abrasivw and as a refractory material .Made by heating silica (`SiO_(2))` witgh `C` in an electric furnace. Benzene is a nonpolar molecules solid, urea is a polar molecules solid and zinc sulphide is an ionic solid. |
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| 534. |
Glass is a:A. Micro-crystalline solidB. Supercooled liquidC. GelD. Polymeric mixture |
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Answer» Correct Answer - B Glass is a supercooled liquid , which forms a non-crystalline solid |
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| 535. |
Why is FeO (s) Not formed in stocihimetric composition ? |
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Answer» Correct Answer - This is because some `Fe^(2+)` ions in FeO are replaced by ` Fe^(3+)` ions. As ` 3 Fe^(2+)` ions are replaced by 2` Fe^(3+)` ions to maintain electrical neutality, there is less amount of metal as compared to stocihonmetric proportion . |
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| 536. |
which one of the following is a covalent crystal?A. Rock saltB. IceC. QuartzD. Dry ice |
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Answer» Correct Answer - C Rock salt is an ionic crystal , ice and dry ice is a molecular crystal and quartz `(SiO_2)` is a covalent or network crystal . |
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| 537. |
A crystalline solidA. changes abruptly from sold to liquidB. has no definite melting pointC. undergoes deformation of its geometry easilyD. has an regular 3-dimensional arrangement |
| Answer» Correct Answer - 3 | |
| 538. |
A compound AB crystallises in the b.c.c lattice with unit cell edge length of 390 pm. Calculate (a) the distance between the oppsitely charged ions in the lattice. (b) the radius of `A^(+)` ion if radius of `B^(-)` ion is 175 pm. |
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Answer» Correct Answer - (a) 195 pm (b) 128.1 pm (a) Distance between the oppositely charged ions in the lattice `=(("390 pm"))/(2)` = 195 pm. (b) For a cubic unit cell, `(r_(A^(+)))/(r_(B^(-)))=0.732` `r_(A^(+))=0.732xxr_(B^(-))=0.723xx("175 pm")=128.1 "pm"` |
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| 539. |
Crystalline solidA. Changes abrupty from solid to liquidB. Has no definite melting pointC. Undergoes deformation of its geometry easilyD. Has an irregular 3-dimensional arrangement |
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Answer» Correct Answer - A A crystalline solid is composed of atoms arranged in an orderly repetitive array. A crystalline solid changes abruptly form solid to liquid . E.g. Cu, Ag, Fe etc. , are crystalline solid |
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| 540. |
A compound `M_(p)X_(q)` has cubic close packing `(ccp)` arrangement of `X`. Its unit cell structure is shown below. The empirical formula of the compound is A. MXB. `MX_(2)`C. `M_(2)X`D. `M_(5)X_(14)` |
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Answer» Correct Answer - B No. of M atoms `=(1)/(4)xx4+1=1+1=2` No. of X atoms `=(1)/(2)xx6+(1)/(8)xx8+3+1=4` So formula `=M_(2)X_(4)=MX_(2)` |
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| 541. |
Which of the following exists as covalent crystals in the solid state?A. IodineB. SiliconC. SulphurD. Phosphorus |
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Answer» Correct Answer - B Silicon exists as covalent crystal in solid state, having network like structure , as in diamond. |
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| 542. |
`ZnO` is white cold and yellow when heated, it is due to the development ofA. Frenkel defectB. Metal defectC. Schonttky defectD. Metal deficiency defect |
| Answer» Correct Answer - b | |
| 543. |
Which of the following compounds is nonstoichiometric ?A. `FeO`B. `Cu_(2)O`C. `Cu_(2)S`D. All of these |
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Answer» Correct Answer - 4 Various lattice defects occur during crystllization. Crystal planes may be misaligned or sites in the crystal lattice may reamain vacant. It is also possible to have an unequal number of cation and anion vacancies in an ionic crystal. For example, iron (II) oxide.`FeO` usually crystallizes with some iron (II) sites left unoccupied. Enough of the remaining `Fe` atoms have `+3` charges to gives an electrically balanced crystal.As a result there are more oxygen atoms then `Fe` atoms in the crystal . Moreover, the exact composition of the crystal can vary, so the formula `FeO` is only approximate, Such a compound whose composition varies slightly from its idealized formula is said to be nonstoichiometric. Other Example of nonstoichiometric compounds are `Cu_(2)O` and `Cu_(2)S`. Each usually has less `Cu` than expected from the formula.The newly discovered ceramic materials having superconducting properties at relatively high temperatures are nonstoichiometric compound. An example is yttrium barium copper oxide ,`YBa_(2)CU_(3)O_(7-x)` where `x` is approximately `0.1`. It is a compound with `O` atom vacancies. |
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| 544. |
Which of the following exists as covalent crystals in the solid state?A. SiB. NaFC. AlD. At |
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Answer» Correct Answer - A Silicon is a covalent crystal in which constituent particles are atoms. |
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| 545. |
The arrangement of `X^(ɵ)` ions around `A^(o+)` ion in solid `AX` is given in the figure (not drawn to scale). If the radius of `X^(ɵ)` is `250 pm`, the radius of `A^(o+)` is A. 104pmB. 125pmC. 183pmD. 57pm |
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Answer» Correct Answer - A The given arrangement is octahedral void arrangement. `rarr (r_(A)^(+))/(r_(X^(-)))ge0.414rArrr_(A)^(+)ge0.414xx250` `r_(A)^(+)ge103.5`pm `& (r_(A)^(+))/(r_(A)^(-))lt0.732rArrr_(A)^(+)lt183`pm |
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| 546. |
Zinc oxide is white in colour at room temperature but turns yellow when heated on account ofA. metal excess defect due to anionic vacanciesB. metal excess defect due to the presence of extra cations at interstitial sites.C. metal deficiency defect due to absence of positive ionsD. metal deficiency defect due to extra interstitial negative ions |
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Answer» Correct Answer - 2 Zinc oxide loses oxygen reversibly at high temperature and turns yellow in colours `ZnO overset("heating")rarr Zn^(2+)+(1)/(2)O_(2)+2e^(-)` The excess metal is accommodated interstitially giving rise toe elctrons trappe din the neightbourhood,these electrons absorb energy from the visible light falling on the crystals. giving yellow colour to `ZnO`. The enhanced electrical conductivity of the nonstoichiometric `ZnO` arises from these electrons. |
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| 547. |
The packing efficiency of the two dimensional square unit cell shown below is: A. 0.3927B. 0.6802C. 0.7405D. 0.7854 |
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Answer» Correct Answer - D Contribution of circle from corner of the square =1/4 Effective no. of circles per square`=((1)/(4)xx4)+1=2` `P.F.=("Area occupied by circles")/("Area of the square")=` |
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| 548. |
The arrangement of `X^(ɵ)` ions around `A^(o+)` ion in solid `AX` is given in the figure (not drawn to scale). If the radius of `X^(ɵ)` is `250 pm`, the radius of `A^(o+)` is A. 104 pmB. 125 pmC. 183 pmD. 57 pm |
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Answer» Correct Answer - A Cation in octahedral voids `(r^(+))/(r^(-))=0.414` (without distortion), `(r^(+))/(250)=0.414` `r^(+)=0.414 250 =103.5 =104` (approx) |
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| 549. |
Zinc oxide is white but it turns yellow on heating . Explain. |
| Answer» When ZnO is heated, it loses oxygen according ot reaction : ` ZnO to Zn^(2+) + 1/2 O^(2) + 2^(e-) Zn^(2+)` ions are entrapped in the interstitial voids and electrons in the neighbouring interestitial voids to maintain electrical neutulity . This gives rise to metal excess defect. Due to presence of electrons in the intersitial voids( F-centres), the colour is yellow as the remaining colours of while light are absorbed by these electrons. | |
| 550. |
Co-ordination number (CN) of barium ion `(Ba^(2+))` in `BaF^(2)` is 8. What is the CN of `F^(-)` ion ? |
| Answer» C.N. of barium ion tells us that it is surrounded by eight fluoride ions (charge `8 xx (-1) = -8`). In order to balance out the eight negative charges, we need four barium ion (charge `4 xx (+2) = +8`). Hence, the C.N. of `F^(-)` ions must be 4 | |