Chemistry

The Solid State

Question:

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

Answer:

Metallic solids

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The Solid State

Q 1.

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

Q 2.

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

Q 3.

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 4.

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 5.

What types of stoichiometric defects are shown by (C.B.S.E. Delhi 2013)
(i) ZnS
(ii) AgBr?

Q 6.

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

Q 7.

 Define the term ‘amorphous’. Give a few examples of amorphous solids.

Q 8.

 ‘Stability of a crystal is reflected in the magnitude of its melting points’. Comment. Collect melting points of solid water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?

Q 9.

Ferric oxide crystallises in a hexagonal dose- packed array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Derive the formula of the ferric oxide.

Q 10.

Aluminium crystallises in a cubic close packed structure. Its metallic radius is 125 pm.

  1. What is the length of the side of the unit cell?
  2. How many unit cells are there in 1.00 cm3 of aluminium?

Q 11.

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 12.

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

Q 13.

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

Q 14.

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 15.

Classify each of the following as being either a p-type or n-type semiconductor :

  1. Ge doped with In
  2. B doped with Si.

Q 16.

 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 17.

 (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 18.

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

Q 19.

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 20.

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 21.

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 22.

 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 23.

 Explain:
(i) The basis of similarities and differences between metallic and ionic crystals.
(ii) Ionic solids are hard and brittle.

Q 24.

Explain the following terms with suitable examples :

  1. Schottky defect
  2. Frenkel defect
  3. Interstitial defect
  4. F-centres.

Q 25.

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 26.

A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong?

Q 27.

 How many lattice points are there is one unit cell of each of the following lattices?
(i) Face centred cubic (if) Face centred tetragonal (iii) Body centred cubic

Q 28.

 Distinguish between :
(i) Hexagonal and monoclinic unit cells
(ii) Face-centred and end-centred unit cells.

Q 29.

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

Q 30.

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

Q 31.

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 32.

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 33.

Classify .the following solids in different categories based on the nature of intermolecular forces operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide

Q 34.

Give the significance of a ˜lattice point'.

Q 35.

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

Q 36.

What type of stoichiometric defect is shown by:
(i)ZnS (ii)AgBr

Q 37.

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

Q 38.

(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 39.

Name the parameters that characterise a unit cell.

Q 40.

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 41.

Classify each of the following solids as ionic, metallic, modular, network (covalent) or amorphous:
(i) Tetra phosphorus decoxide (P4O10) (ii) Ammonium phosphate, (NH4)3P04 (iii) SiC (iv) I2 (v) P4  (vii) Graphite (viii), Brass (ix) Rb (x) LiBr (xi) Si

Q 42.

Iodine molecules are held in the crystals lattice by
(a) London forces (b) dipole-dipole interactions
(c) covalent bonds (d) coulombic forces

Q 43.

 How can you determine the atomic mass of an unknown metal if you know its density and dimensions of its unit cell ? Explain your answer. (C.B.S.E. Outside Delhi 2011)

Q 44.

Why are solids rigid?

Q 45.

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 46.

Solid A is a very hard electrical insulator in. solid as well as in molten state and melts at  extremely high temperature. What type of solid is it?

Q 47.

A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy l/3rd of tetrahedral voids. What is the formula of the compound?

Q 48.

What type of substances would make better permanent magnets, ferromagnetic or ferrimagnetic. Justify your answer.

Q 49.

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 50.

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.