Chemistry

The Solid State

Question:

What is the two-dimensional coordination number of a molecule in square close-packed layer?

Answer:

In 2D, square close-packed layer, an atom touches 4 nearest neighbouring atoms. Hence, its CN=4

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The Solid State

Q 1.

Explain why does conductivity of germanium crystals increase on doping with gallium?

Q 2.

If NaCI is doped with 10-3 mol % SrCl2, what is the concentration of cation vacancies?

Q 3.

What is the coordination number in a square close packed structure in two dimensions?  (a) 2 (b) 3 (c) 4 (d) 6

Q 4.

Silver crystallises in fcc lattice. If edge length of the cell is 4.07 x 10-8 cm and density is 10.5 g cm-3, calculate the atomic mass of silver.

Q 5.

Assertion (A): The packing efficiency is maximum for the fee structure. Reason (R): The coordination number is 12 in fee structures.

Q 6.

What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?

Q 7.

Classify each of the following solids as ionic, metallic, modular, network (covalent), or amorphous:
(i) Tetra phosphorus decoxide (P4O10) (ii) Ammonium phosphate, (NH4)3PO4 (iii) SiC (iv) I2 (v) P(vii) Graphite (viii), Brass (ix) Rb (x) LiBr (xi) Si

Q 8.

The total number of tetrahedral voids in the face centered unit cell is
(a) 6 (c) 10
(b) 8 (d) 12

Q 9.

Which of the following statements are true about metals?
(a) Valence band overlap with conduction band
(b) The gap between valence band and conduction band is negligible
(c) The gap between valence band and conduction band cannot be determined
(d) Valence band may remain partially filled.

Q 10.

What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?

Q 11.

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.

Q 12.

The number of tetrahedral voids per unit cell in NaCl crystal is
(c) twice the number of octahedral voids
(d) four times the number of octahedral voids

Q 13.

Why do solids have a definite volume?

Q 14.

A compound forms hexagonal close-packed. structure. What is the total number of voids in  0. 5 mol of it? How many of these are tetrahedral voids?

Q 15.

Copper crystallises into a fee lattice with edge length 3.61 x 10-8 cm. Show that the calculated density is in agreement with its measured value of 8.92 gcm-3.

Q 16.

Which of the following represents correct order of conductivity in solids?
ncert-exemplar-problems-class-12-chemistry-solid-state-22

Q 17.

Why does the electrical conductivity of semiconductors increase with rise in temperature?

Q 18.

Under which situations can an amorphous substance change to crystalline form?

Q 19.

 A compound forms hexagonal close-packed. structure. What is the total number of voids in 0. 5 mol of it? How many of these are tetrahedral voids?

Q 20.

Analysis shows that nickel oxide has the formula Ni0.98 O1.00. What fractions of nickel exist as Ni2+ and Ni3+ ions?

Q 21.

Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?

Q 22.

Gold (atomic radius = 0.144 nm) crystallises in a face centred unit cell. What is the length of the side of the unit cell ?

Q 23.

Why is glass considered a supercooled liquid?

Q 24.

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?

Q 25.

What type of solids are electrical conductors, malleable and ductile?

Q 26.

Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

Q 27.

Define the term amorphous'. Give a few examples of amorphous solids.

Q 28.

What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

Q 29.

(i) What is meant by the term coordination number’?
(ii) What is the coordination number of atom
(a) in a cubic close-packed structure?
(b) in a body centred cubic structure?

Q 30.

How will you distinguish between the following pairs of terms:
(i) Cubic close packing and hexagonal close packing?
(ii) Crystal lattice and unit cell?
(iii) Tetrahedral void and octahedral void?

Q 31.

If the radius of the octahedral void is r and radius of the atoms in close-packing is R, derive relation between rand R.

Q 32.

Which of the following is not a characteristic of a crystalline solid?
(a) Definite 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

Q 33.

Which of the following arrangement shows schematic alignment of magnetic moments of antiferromagnetic substances?
ncert-exemplar-problems-class-12-chemistry-solid-state-4

Q 34.

Which of the following cannot be regarded as molecular solid?
(a) SiC (b) AIN
(c) Diamond (d) I2

Q 35.

Why are solids incompressible?

Q 36.

In a compound, nitrogen atoms (N) make cubic close packed lattice and metal atoms (M) occupy one-third of the tetrahedral voids present. Determine the formula of the compound formed by M and N?

Q 37.

Assertion (A): Total number of octahedral voids present in unit cell of cubic close packing including the one that is present at the body centre, is four. Reason (R): Besides the body centre, there is one octahedral void present at the centre of each ofthe six faces of the unit cell and each of which is shared between two adjacent unit cells.

Q 38.

Assertion (A): Semiconductors are solids with conductivities in the intermediate range from
ncert-exemplar-problems-class-12-chemistry-solid-state-51
Reason (R): Intermediate, conductivity in semiconductor is due to partially filled valence band.

Q 39.

Explain how many portions of an atom located at
(i)corner and (ii)body centre of a cubic unit cell is part of its neighbouring unit cell.

Q 40.

A compound is formed by two elements M and N. The element N forms ccp and atoms of the element M occupy 1/3 of the tetrahedral voids. What is the formula of the compound? (C.B.S.E. Foreign 2015)

Q 41.

 Wh ich of the following lattices has the highest packing efficiency (i) simple cubic (ii) body-centered cubic and (iii) hexagonal close-packed lattice?

Q 42.

Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.

Q 43.

 Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

Q 44.

Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

Q 45.

A cubic solid is made of two elements P and Q. Atoms Q are at the corners of the cube and P at the body centre. What is the formula of the compound ? What is the co-ordination number of P and Q?

Q 46.

Niobium crystallises in a body centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium, using its atomic mass 93u.

Q 47.

What are semi-conductors? Describe the two main types of semiconductors and contrast their conduction mechanisms.

Q 48.

Why are solids rigid?

Q 49.

Explain how much portion of an atom located at
(i)corner and (ii)body centre of a cubic unit cell is part of its neighbouring unit cell.

Q 50.

Which of the following lattices has the highest packing efficiency (i) simple cubic (ii) body- centred cubic and (iii) hexagonal close-packed lattice?