NCERT solutions Chemistry Textbook for Class 12 Part 1 chapter 1 The Solid State



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Chapter 1 - The Solid State

Pages 4 - 29

Why are solids rigid?

Q 1 | Page 4 |

Why do solids have a definite volume?

Q 2 | Page 4 |

Classify the following as amorphous or crystalline solids:

Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.

Q 3 | Page 4 |

Why is glass considered a super cooled liquid?

Q 4 | Page 4 |

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 5 | Page 4 |

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 6 | Page 6 |

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 7 | Page 6 |

Ionic solids conduct electricity in molten state but not in solid state. Explain

Q 8 | Page 6 |

Give the significance of a ‘lattice point’.

Q 10 | Page 12 |

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

Q 14 | Page 21 |

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 | Page 21 |

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

Q 17 | Page 22 |

An element with molar mass 2.7 × 10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 × 103 kg m−3, what is the nature of the cubic unit cell?

Q 18 | Page 22 |

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

Q 19 | Page 29 |

What type of stoichiometric defect is shown by:

(i) ZnS 

(ii) AgBr

Q 20 | Page 29 |

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

Q 21 | Page 29 |

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 23 | Page 29 |

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

Q 24 | Page 29 |

Pages 30 - 32

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

Q 1 | Page 30 |

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

Q 2 | Page 30 |

Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous.

(i) Tetra phosphorus decoxide (P4O10

(ii) Ammonium phosphate (NH4)3PO4 

(iii) SiC 

(iv) I2 

(v) P4 

(vii) Graphite

(viii) Brass

(ix) Rb

(x) LiBr

(xi) Si


Q 3 | Page 30 |

What is meant by the term 'coordination number'?

Q 4.1 | Page 30 |

What is the coordination number of atoms:

(a) in a cubic close-packed structure?

(b) in a body-centred cubic structure?

Q 4.2 | Page 30 |

How can you determine the atomic mass of an unknown metal if you know its density and the dimension of its unit cell? Explain.

Q 5 | Page 30 |

'Stability of a crystal is reflected in the magnitude of its melting point'. 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 6 | Page 30 |

How many lattice points are there in one unit cell of each of the following lattice?

(i) Face-centred cubic

(ii) Face-centred tetragonal

(iii) Body-centred

Q 8 | Page 31 |

Explain The basis of similarities and differences between metallic and ionic crystals.

Q 9.1 | Page 31 |

Explain Ionic solids are hard and brittle.

Q 9.2 | Page 31 |

Calculate the efficiency of packing in case of a metal crystal for simple cubic

Q 10.1 | Page 31 |

Calculate the efficiency of packing in case of a metal crystal for body-centred cubic

Q 10.2 | Page 31 |

Calculate the efficiency of packing in case of a metal crystal for face-centred cubic (with the assumptions that atoms are touching each other).

Q 10.3 | Page 31 |

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

Q 11 | Page 31 |

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

Q 12 | Page 31 |

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

Q 13 | Page 31 |

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

Q 14 | Page 31 |

Copper crystallises into a fcc lattice with edge length 3.61 × 10−8 cm. Show that the calculated density is in agreement with its measured value of 8.92 g cm−3.

Q 15 | Page 31 |

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

Q 16 | Page 31 |

What is a semiconductor

Q 17.1 | Page 31 |

Describe the two main types of semiconductors and contrast their conduction mechanism.

Q 17.2 | Page 31 |

Ferric oxide crystallises in a hexagonal close-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 19 | Page 31 |

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

Ge doped with In

Q 20.1 | Page 31 |

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

B doped with Si.

Q 20.2 | Page 31 |

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

Q 21 | Page 32 |

In terms of band theory, what is the difference Between a conductor and an insulator

Q 22.1 | Page 32 |

In terms of band theory, what is the difference Between a conductor and a semiconductor

Q 22.2 | Page 32 |

Define the following term

Schottky defect

Q 23.1 | Page 32 |

Explain the following terms with suitable examples: Frenkel defect

Q 23.2 | Page 32 |

Explain the following terms with suitable examples : Interstitials

Q 23.3 | Page 32 |

Explain the following terms with suitable examples: F-centres

Q 23.4 | Page 32 |

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

(i) What is the length of the side of the unit cell?

(ii) How many unit cells are there in 1.00 cm3 of aluminium?

Q 24 | Page 32 |

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

Q 25 | Page 32 |

What is ferromagnetism?

Q 26.1 | Page 32 |

Explain the following with suitable examples: Paramagnetism

Q 26.2 | Page 32 |

Explain the following with suitable examples: Ferrimagnetism

Q 26.3 | Page 32 |

Explain the following with suitable examples: Antiferromagnetism

Q 26.4 | Page 32 |

Explain the following with suitable examples:

12-16 and 13-15 group compounds.

Q 26.5 | Page 32 |

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