Chemistry Interview Questions GK Questions

Chemistry Interview Questions GK Questions

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01.	Class 12 Chemistry Important Questions
02	Very Important Questions for Class 12 Chemistry
03	Important Questions for Class 12 Chemistry Chapter 1 The Solid State
04	Solid State Class 12 Important Questions and Answers
05	Chemistry Solid State Class 12 Important Questions and Answers PDF
06	Solid State Class 12 Important Questions With Answers PDF
07	Solid State Questions And Answers PDF
08	Solid State Questions for Class 12 Chemistry
09	Solid State Class 12 Important Questions With Answers
10	Top Solid State Chemistry Questions and Answers PDF

SOLID STATE

1. In the cubic arrangement the radius ratio is found to be 0.884. The structure of the crystal will be
   Ans. Body centered cubic
2. Radius ratio of NaCl crystal is 0.532. The structure of the crystal is
   Ans. Octahedral

3.Number of particles present per unit cell of HCP crystal is
Ans. Six

4. Iodine is an example of type of solid.
   Ans. Molecular
5. The point defect which decreases the density of a solid is called as
   Ans. schottky defect
6. Give an example of hcp and bcc crystal.
   Ans. hcp ZnS, ZnOP
   bcc = CsCI, CsBr
7. Find the number of atoms per unit cell in a face centered cubic structure having only single atoms at its lattice point.
   Ans. For Fcc unit cell, no of atoms per unit cell
   = 8(corners)x 1/8+6(faces)x 1/2= 1 +3 =4
8. Name the point defect responsible for colour in alkali metal halides.
   Ans. The defect is called as metal excess defect. Due to this F-centres are created which is responsible for colour in alkali metal halides.
9. Name the element with which Germanium may be doped to produce n-type semi-conductor
   Ans. Arsenic (Gr-15)
10. When Indium is added to Germanium which type of semiconductor is formed ?
    Ans. Indium (Gr-13) when added to Germanium (Gr-14) then p-type of semiconductor is formed.
11. Write the Bragg’s equation
    Ans. nμ = 2d sin ∅
    where n = order of diffraction
    A= wave length of monochromatic light
    d= distance between two parallel planes containing constituent
    ∅= angle of diffraction
12. Write two characteristies of ionic solid
    Ans. These are water soluble, possess high mp and bp, usually hard and brittle.
13. In molecular solid the constituent particles are held together by.
    Ans. vander Waal’s force of attraction.
14. Carborandum is a__type of solid while dry ice is a ___type of solid.
    Ans. Covalent, molecular.
15. Which type of crystalline solids are good conductor of electricity ?
    Ans. Metallic crystals
16. In a simple cubic crystal packing efficiency is
    Ans. 52.4%
17. In which type of cubic crystal arrangement packing efficiency is maximum ?
    Ans. Face centered cubic crystal (74%)
18. Which type of crystal defect decreases density of a crystal ?
    Ans. Schottky defect.
19. If there are “N tetrahedral voids, then number of octahedral voids is
    Ans. N/2
20. Octahedral void is created by lattice points
    Ans. Six
21. Number of atoms in FCC crystal is
    Ans. 1+3 =4 atoms
22. Which type of crystal defect increases the density of a solid 2
    Ans. interstitial defect.
23. do metallic solid and ionic solid differ in conducting property ?
    Ans. Metallic solids conduct electricity due to movement of electrons and conductivity decreases with increase in temperature. lionic solids conduct electricity due to movement of ions only in fused state or in aqueous solution. The conductivity increases with increase in
    temperature.
24. Which type of erystal defect does not change the density of solid ?
    Ans. Frenkel defect.
25. What type of semiconductor is formed when silicon is doped with arsenic ?
    Ans. n-type semiconductor
26. What is F-centres ?
    Ans. It is a centre where the electron is entrapped in the anion vacances. This type of crystal defect is also
    known as metal excess defect.
27. What type of semiconductor is formed when silicon is doped with Gallium ?
    Ans.p-type semiconductor
28. Write one application of semiconductor.
    Ans. Semiconductors are used in transistors to detect and amplify radio signals. There are also used in photovoltaic cell to convert light energy to electrical energy.
29. Name the type of structure possessed by unit cell of CsCl.
    Ans. Body centered cubic (bcc) structure.
30. How does electrical conductivity vary with temperature for semiconductors
    Ans. The electrical conductivity increases with increase in temperature for semiconductors due to increase in kinetic energy of electrons.
31. What type of crystal defects are shown by ZnS.
    Ans. Frankel defect is shown by ZnS as the cationic SIze is less than the anionic size.
32. What type of crystal defects are shown by AgBr?
    Ans. AgBr shows both Frenkel and Schottky defects.
33. How many Chloride ions are there around Sodium ion in sodium chloride crystal
    Ans. Six

34.How will you distinguish between tetrahedral void and octahedral void 2
Ans. Tetrahedral void is surrounded by four spheres which lie at the vertices of a regular tetrahedron.Octahedral void is surrounded by six spheres, which lie at the vertices of a regular octahedron.

35. What is co-ordination number?
    Ans. Co-ordination number is the number of nearest neighbours with which an atom is in contact. e.g. In a body centred cubic structure the co-ordination number is 8.
36. Write the equation by which you can find atomic mass of a metal from its density and dimensions of unit cell.
    Ans. M =Pa³Na/Z
    where p = density
    a edge length of unit cell
    z number of atoms in unit cell
    NÀ =Avogadro’s number
37. An ionic compound has a unit cell consisting of A ions at the corners of a cube and B ions on the centres of the faces of the cube. What is the empirical formula of the compound?
    Ans. Number of A ions per unit cell=x8 (corners) = 1 Number of B ions per unit cell =X6 (faces) = 3
    So the empirical formula of the compound is AB, .
38. What is n-type semiconductor
    Ans. When a silicon crystal is doped with atoms of
    Gr 15 elements (P, As, etc) then four valency electrons
    of each impurity atom form cOvalent bonds with silicon
    atoms. Since there is a free electron which is used for
    conduction, so it is called as n-type semiconductor.
39. Gold crystalises in a fcc structure, what is the
    edge length of the unít cell ? Given radius of gold
    atom is 0.144 nm
    Ans. For Fcc unit cell, r= √2a/4
    a = 4r/√2=2√2r
    = 2×1.414×0.144
    =0.4973nm
40. What type of forces operate in molecular solids?
    Ans. vander Waal’s force, dipole dipole interaction
    or hydrogen bonds may operate between the molecules
    of molecular solid.
41. Write two characteristic properties of molecular
    solid.
    Ans. These are generally soft and have low density. These are bad conductor of heat and electricity
42. Write two characteristic properties of ionic solid.
    Ans. These are soluble in water These are hard and brittle
    These are good conductor of electricity in molten state or aqueous solution.
43. What type of solids are electrical conductor and malleable ?
    Ans. Metallic solids
44. What type of solids are very hard and electrical insulator in solid state as well as in moten state?
    Ans. Covalent solids
45. What do you mean by packing efficiency ? In which type of crystal arrangements packing efficiency is more ?
    Ans. The percentage of total space filled by the particle in a crystal is called as packing efficiency. The packing efficiency is more in a face centred cubic structure (74%).
46. Khat type of stoichiometric defect is shown by ZnS?
    Ans. Frankel defect.
47. What type of stoichiometric defect is shown by AgBr ?
    Ans. Frankel defect as well as Schottky defect.
48. What is meant by point defect in crystals ?
    Ans. The defects in crystals arises due to the irregularity in arrangement of atoms or ions are called as point defects
49. If ‘a’ is the edge length of the unit cell of a fcc crystal, then what is the distance of closest approach between the two atoms in the crystal 2
    Ans. In a fec crystal 4r = √2a
    2r= a/√2 or d= a/√2
    where d= distance of closest approach between two atoms.
50. An a bcc crystal what is the relationship between
    atomic radius (r) and edge length (a) ?
    Ans. r=a(√3/4)
51. What is the packing efficiency in a bcc arrangement of crystals ?
    Ans. 68%

Important Questions for Class 12 Chemistry Chapter 1 The Solid State Class 12 Important Questions

Question 1.
Which point defect in crystals does not alter the density of the relevant solid?
Answer:
Frenkel defect.

Question 2.
Which point defect in its crystal units alters the density of a solid?
Answer:
Schottky defect.

Question 3.
Which point defect in its crystal units increases the density of a solid?
Answer:
Metal excess defect increases the density of a solid. It is due to presence of extra cations in the interstitial sites.

Question 4.
How do metallic and ionic substances differ in conducting electricity?
Answer:
The electrical conductivity in metallic substances is due to free electrons while in ionic substances the conductivity is due to presence of ions.

Question 5.
Which point defect of its crystals decreases the density of a solid?
Answer:
Schottky defect.

Question 6.
What is the number of atoms in a unit cell of a face-centred cubic crystal?
Answer:
The number of atoms in a unit cell of fcc-crysta! is 4 atoms.

Question 7.
Write a feature which will distinguish a metallic solid from an ionic solid.
Answer:
The electrical conductivity in metallic solid is due to free electrons while in ionic solid the conductivity is due to presence of ions.

Question 8.
Which point defect in crystals of a solid does not change the density of the solid?
Answer:
Frenkel defect.

Question 9.
Which point defect in crystals of a solid decreases the density of the solid?
Answer:
Schottky defect.

Question 10.
What type of interactions hold the molecules together in a polar molecular solid?
Answer:
Dipole-dipole forces of attractions hold the molecules together in a polar molecular solid.

Question 11.
What type of semiconductor is obtained when silicon is doped with arsenic?
Answer:
n-type semiconductor.

Question 12.
Write a distinguishing feature of metallic solids.
Answer:
Metallic solids possess high electrical and thermal conductivity due to presence of free electrons.

Question 13.
‘Crystalline solids are anisotropic in nature.’ What does this statement mean?
Answer:
It means that crystalline solids show different values of their some properties like electrical conductivity, refractive index, thermal expansion etc. in different directions.

Question 14.
Which stoichiometric defect in crystals increases the density of a solid?
Answer:
Interstitial defect in crystals increases the density of a solid.

Question 15.
What is meant by ‘doping’ in a semiconductor?
Answer:
Addition of a suitable impurity to a semiconductor to increase its conductivity is called doping.

Question 16.
Write a point of distinction between a metallic solid and an ionic solid other than metallic lustre.
Answer:
Metallic solid conducts electricity in solid state but ionic solids do so only in molten state or in solution or metals conduct electricity through electrons and ionic substances through ions. Metallic solids are malleable and ductile while ionic solids are hard and brittle.

Question 17.
How may the conductivity of an intrinsic semiconductor be increased?
Answer:
The conductivity is increased by adding an appropriate amount of suitable impurity. This process is called as intrinsic doping.

Question 18.
Which stoichiometric defect increases the density of a solid?
Answer:
Interstitial defect increases the density of a solid.

Question 19.
What are n-type semiconductors?
Answer:
n-type semiconductor : They are obtained by doping silicon with an element of group15, like P, As etc.

Question 20.
What type of stoichmetric defect is shown by AgBr and Agl ?
Answer:
AgBr shows both Frenkel defect and Schottky defect whereas Agl shows Frenkel defect.

Question 21.
What type of defect can arise when a solid is heated ?
Answer:
Vacancy defects can arise when a solid is heated.

Question 22.
Why does LiCl acquire pink colour when heated in Li vapours?
Answer:
This is due to metal excess defect due to anionic vacancies in which the anionic sites are occupied by unpaired electrons (F-centres).

Question 23.
How many atoms constitute one unit cell of a face-centered cubic crystal?
Answer:
4 atoms constitute one unit cell of a fee crystal.

Question 24.
What type of stoichiometric defect is shown by AgCl?
Answer:
Frenkel defect is shown by AgCl.

Question 25.
What type of substances would make better Permanent Magnets: Ferromagnetic or Ferrimagnetic?
Answer:
Ferromagnetic substances would make better I permanent magnets
Example : Fe, Co, Ni etc.

Question 26.
Calculate the number of atoms in a face centred cubic unit cell.
Answer:
In face centered cubic arrangement, number of lattice points are : 8 + 6.
∴ Lattice points per unit cell = 8×18+6×12 = 4

Question 27.
On heating a crystal of KC1 in potassium vapour, the crystal starts exhibiting a violet colour. What is this due to?
Answer:
The Cl ions diffuse to the surface and combine j with atoms which get ionized by losing electrons. ! These electrons are trapped in anions vacancies j and act as F-centre which imparts violet colour to the crystal.

Question 28.
Which type of ionic substances show Schottky defect in solids?
Answer:
Highly ionic compounds with high coordination rjuniber and small difference in size of cations and anions show schottky defect.

Question 29.
How many atoms per unit cell (z) are present in bcc unit cell?
Answer:
Number of atoms in a unit cell of a body centred cubic structure :
Contribution by 8 atoms on the corners
= 18 × 8 = 1
Contribution by the atom presents within the body = 1
∴ Total number of atoms present in the unit cell = 1 + 1 = 2 atoms

Question 30.
What type of stoichiometric defect is shown by NaCl?
Answer:
Schottky defect is shown by NaCl.

Question 31.
Write a distinguishing feature between a metallic solid and an ionic solid.
Answer:
The electrical conductivity in metallic substances is due to free electrons while in ionic substances the conductivity is due to presence of ions.

Question 32.
Why are crystalline solids anisotropic?
Answer:
Crystalline solids show different values of their some properties like electrical conductivity, refractive index, thermal expansion etc. in different directions.

Question 33.
What is meant by ‘antiferromagnetism’?
Answer:
Antiferromagnetism : These substances possess zero net magnetic moment because of presence of equal number of electrons with opposite spins.

Question 34.
Write a distinguishing feature of a metallic solid compared to an ionic solid.
Answer:
Metallic solid conducts electricity in solid state but ionic solids do so only in molten state or in solution or metals conduct electricity through electrons and ionic substances through ions. Metallic solids are malleable and ductile while ionic solids are hard and brittle.

Question 35.
What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3rd of tetrahedral voids?
Answer:
Formula is X₂Y₃.

Question 36.
What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 2/3rd of tetrahedral voids?
Answer:
Y atoms are N (No. of tetrahedral voids are 2N), No. of tetrahedral voids occupied by X are
23 × 2N = 4N3
X : Y = 4N : 3N
Formula : X₄Y₃

Question 37.
What is the no. of atoms per unit cell (z) in a body-centred cubic structure?
Answer:
Contribution by the atoms present at eight comers = 8 × 18 = 1
Contribution by the atoms present at centre = 1
Total number of atoms present in unit cell = 1 + 1 = 2

Question 38.
What type of stoichiometric defect is shown by AgCl?
Answer:
AgCl shows Frenkel defect.

Question 39.
What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction?
Answer:
Ferromagnetism is shown by a substance if magnetic moments of domains are arranged in same direction.

Question 40.
Give an example each of a molecular solid and an ionic solid.
Answer:
Molecular solid → Iodine (I₂)
Ionic solid → Sodium chloride (NaCl)