Table salt, NaCl, sometimes appear yellow due to excessive corrosion of the metal. Free electrons are trapped in anion gaps. When electrons absorb energy, they are excited and falls off the crystal.
Why is FeO (s) not formed in stoichiometric composition?
Composition of Fe2+ and O2 ions is 0:95:1 because few of the Fe2+ ions gets replaced by Fe3+ ions in the OH site of the FeO.
Why does white ZnO (s) become yellow upon heating?
On heating, ZnO gives Zn2+electrons and because of this electron and the conductivity of the crystal the white ZnO turns into yellow in colour.
Why does the electrical conductivity of semiconductors increase with a rise in temperature?
The energy gap between the valence bond and the conduction bond is small, at room temperature it does not generate electricity but raises electrons to obtain a sufficient amount of energy to be...
Which of the following statements are not true?
(i) Vacancy defect results in a decrease in the density of the substance. (ii) Interstitial defects increase the density of the substance. (iii) Impurity defect does not affect the density of the...
The value of the magnetic moment is zero in the case of antiferromagnetic substances because the domains ________.
(i) get oriented in the direction of the applied magnetic field. (ii) get oriented opposite to the direction of the applied magnetic field. (iii) are oppositely oriented with respect to each other...
Which of the following is not true about the voids formed in 3-dimensional hexagonal close-packed structure?
(i) A tetrahedral void is formed when a sphere of the second layer is present above triangular void in the first layer. (ii) All the triangular voids are not covered by the spheres of the second...
Which of the following represents correct order of conductivity in solids?
(i) κ metals >> κ insulators< κsemiconductors (ii) κmetals<< κinsulators < κsemiconductors (iii) κmetals κsemiconductors> κinsulators = zero (iv) κ metals< κ semiconductors...
The edge lengths of the unit cells in terms of the radius of spheres constituting fcc,bcc and simple cubic unit cell are respectively________
(i) 2√2r, 4r/√3, 2r (ii) 4r/√3, 2√2r, 2r (iii) 2r, 2√2r, 4r/√3 (iv) 2r, 4r/√3, 2√2r Correct Answer: (i) 2√2r, 4r/√3, 2r Explanation: In fcc, a = 2√2r In bcc, a = 4r/√3 In simole cubic,...
In the cubic close packing, the unit cell has ________.
(i) 4 tetrahedral voids each of which is shared by four adjacent unit cells. (ii) 4 tetrahedral voids within the unit cell. (iii) 8 tetrahedral voids each of them which are shared by four adjacent...
Which of the following defects is also known as dislocation defect?
(i) Frenkel defect (ii) Schottky defect (iii) Non-stoichiometric defect (iv) Simple interstitial defect Correct Answer: (i) Frenkel defect Explanation: In Frenkel defect, the atom is...
The correct order of the packing efficiency in different types of unit cells is ________.
(i) fcc < bcc < simple cubic (ii) fcc > bcc > simple cubic (iii) fcc < bcc > simple cubic (iv) bcc < fcc > simple cubic Correct Answer: (ii) fcc > bcc >...
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because ________.
(i) all the domains get oriented in the direction of the magnetic field. (ii) all the domains get oriented in the direction opposite to the direction of the magnetic field. (iii) domains get...
Which of the following is not true about the ionic solids?
(i) Bigger ions form the close-packed structure (ii) Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size (iii) Occupation of all the voids is not necessary...
Which of the following statements is not true?
(i) Paramagnetic substances are weakly attracted by the magnetic field (ii) Ferromagnetic substances cannot be magnetised permanently (iii) The domains in antiferromagnetic substances are oppositely...
Silicon doped with electron rich impurity forms ________.
(i) p-type semiconductor (ii) n-type semiconductor (iii) intrinsic semiconductor (iv) insulator Correct Answer: (ii) n-type semiconductor Explanation: N-Type semiconductor is created...
Which kind of defects are introduced by doping?
(i) Dislocation defect (ii) Schottky defect (iii) Frenkel defects (iv) Electronic defects Correct Answer: (iv) Electronic defects Explanation: The doping is done for low electron or...
What is the coordination number in a square close-packed structure in two dimensions?
(i) 2 (ii) 3 (iii) 4 (iv) 6 Correct Answer: (iii) 4 Explanation: Four is the coordination number in a square close-packed structure in two dimensions as the molecules in this structure...
In which of the following structures coordination number for cations and anions in the packed structure will be same?
(i) Cl- Ion form fcc lattice and Na+ ions occupy all octahedral voids of the unit cell. (ii) Ca2+ ions form fcc lattice and F- ions occupy all the eight tetrahedral voids of the unit cell. (iii) O2-...
Which of the following statement is not true about the hexagonal close packing?
(i) The coordination number is 12. (ii) It has 74% packing efficiency. (iii) Tetrahedral voids of the second layer are covered by the spheres of the third layer. (iv) In this arrangement spheres of...
The percentage of empty space in a body centred cubic arrangement is ________.
(i) 74 (ii) 68 (iii) 32 (iv) 26 Correct Answer: (iii) 32 Explanation: Calculation – Empty space in a body-centered arrangement = 100 – 68 Empty space in a body-centered arrangement =...
In which pair most efficient packing is present?
(i) hcp and bcc (ii) hcp and ccp (iii) bcc and up (iv) bcc and simple cubic cell Correct Answer: (ii) hcp and ccp Explanation: Given, Packing efficiency of the lattices: hcp = 74%...
Which of the following point defects are shown by AgBr(s) crystals? (A) Schottky defect (B) Frenkel defect (C) Metal excess defect (D) Metal deficiency defect
(i) (A) and (B) (ii) (C) and (D) (iii) (A) and (C) (iv) (B) and (D) Correct Answer: (i) (A) and (B) Explanation: AgBr shows the defects of Scottky and Frenkel. In AgBr, both Ag+ and...
The total number of tetrahedral voids in the face-centred unit cell is __________.
(i) 6 (ii) 8 (iii) 10 (iv) 12 Correct Answer: (ii) 8 Explanation: In the face-cantered cubic unit cell (FCC), a tetrahedral void is present in the diagonals of the body. There are two...
To get a n-type semiconductor from silicon, it should be doped with a substance with valence__________.
(i) 2 (ii) 1 (iii) 3 (iv) 5 Correct Answer: (iv) 5 Explanation: The n - semiconductor type is formed by adding a small amount of Group-V such as phosphorus (P) or arsenic (As) to the...
Which of the following is true about the charge acquired by p-type semiconductors?
(i) positive (ii) neutral (iii) negative (iv) depends on the concentration of p impurity Correct Answer: (ii) neutral Explanation: The P-type semiconductors have a larger concentration...
Schottky defect is observed in crystals when __________.
(i) some cations move from their lattice site to interstitial sites (ii) the equal number of cations and anions are missing from the lattice (iii) some lattice sites are occupied by electrons (iv)...
Cations are present in the interstitial sites in __________.
(i) Frenkel defect (ii) Schottky defect (iii) Vacancy defect (iv) Metal deficiency defect Correct Answer: (i) Frenkel defect Explanation: Ionic solids that contain significant...
Graphite cannot be classified as __________.
(i) conducting solid (ii) network solid (iii) covalent solid (iv) ionic solid Correct Answer: (iv) ionic solid Explanation: The graphite is an allotrope of carbon and its each atom is...
The lattice site in a pure crystal cannot be occupied by _________.
(i) molecule (ii) ion (iii) electron (iv) atom Correct Answer: (iii) electron Explanation: Pure crystal contains atoms, molecules or ions at lattice sites. Electrons can only enter...
Which of the following oxides shows electrical properties like metals?
(i) SiO2 (ii) MgO (iii) SO2(s) (iv) CrO2 Correct Answer: (iv) CrO2 Explanation: CrO2 is the oxide that shows the electrical property like metal whereas the rest does not show the...
Which of the following oxides behaves as conductor or insulator depending upon temperature?
(i) TiO (ii) SiO2 (iii) TiO3 (iv) MgO Correct Answer: (iii) TiO3 Explanation: TiO3 behaves as a conductor or insulator depending on the temperature due to the difference in the power...
Graphite is a good conductor of electricity due to the presence of __________.
(i) lone pair of electrons (ii) free valence electrons (iii) cations (iv) anions Correct Answer: (ii) free valence electrons Explanation: In graphite one carbon atom is attached to...
Which of the following is not the characteristic of ionic solids?
(i) A very low value of electrical conductivity in the molten state. (ii) Brittle nature. (iii) Very strong forces of interactions. (iv) Anisotropic nature. Correct Answer: (i) A very...
Which of the following solids is not an electrical conductor?
(A) Mg (s) (B) TiO (s) (C) I2 (s) (D) H2O (s) (i) (A) only (ii) (B) Only (iii) (C) and (D) (iv) (B), (C) and (D) Correct Answer: (iii) (C) and (D) Explanation: I2 a strong mole without polar...
Which of the following is a network solid?
(i) SO2 (Solid) (ii) I2 (iii) Diamond (iv) H2O (Ice) Correct Answer: (iii) Diamond Explanation: A solid network or covalent network solid is a chemical compound or element in which atoms are...
Iodine molecules are held in the crystals lattice by ____________.
(i) london forces (ii) dipole-dipole interactions (iii) covalent bonds (iv) coulombic forces Correct Answer: (i) london forces Explanation: London distribution force is a weak link...
The sharp melting point of crystalline solids is due to ___________.
(i) a regular arrangement of constituent particles observed over a short distance in the crystal lattice. (ii) a regular arrangement of constituent particles observed over a long distance in the...
Which of the following statement is not true about amorphous solids?
(i) On heating, they may become crystalline at a certain temperature. (ii) They may become crystalline on keeping for a long time. (iii) Amorphous solids can be moulded by heating. (iv) They are...
Illustrate with examples the limitations of Williamson synthesis for the preparation of certain types of ethers.
Williamson's synthesis is a flexible approach for making symmetrical and unsymmetrical ethers. However, careful reactant selection is required for the synthesis of unsymmetrical ethers. Because the...
Write IUPAC names of the following compounds:
Solutions: (i) 2, 2, 4 -Trimethylpentan – 3 – ol (ii) 5 – Ethylheptane – 2, 4 – diol
How are vitamins classified? Name the vitamin responsible for the coagulation of blood.
Vitamins are divided into two categories based on their solubility in water or fat. (a) Water-Soluble Vitamins: This category includes vitamins that are water-soluble. B vitamins (B1,B2, B12 etc.)...
What type of bonding helps in stabilizing the α-helix structure of proteins?
The H-bonds formed between the -NH group of each amino acid residue and the -OH group of the adjacent turns of the α-helix aid in helix stabilization.
Enumerate the reactions of D-glucose which cannot be explained by its open-chain structure.
(i) The glucose pentaacetate does not react with hydroxylamine. This demonstrates that glucose does not include a free -CHO group. (ii) Aldehydes produce hydrogen sulfite as a byproduct by giving...
What happens when D-glucose is treated with the following reagents? (i)HI (ii) Bromine water (iii)HNO3
(i) When D-glucose is heated with HI for a long time, n-hexane is produced. (ii) D-glucose is converted to D-gluconic acid when it is treated with Bromine water. (iii) After being treated with HNO3,...
What is the basic structural difference between starch and cellulose?
Starch consists of amylopectin and amylose subunits. Amylose has a long linear chain of alpha – D (+)glucose units linked together by a C1-C4 glycosidic bond (alpha -link). Figure :- Amylose While...
What are the hydrolysis products of (i) sucrose and (ii) lactose?
(i) One molecule of α-D glucose and one molecule of β-D fructose are produced when sucrose is hydrolyzed. (b) When lactose is hydrolyzed, it produces beta-D-galactose and beta-D-glucose
What is glycogen? How is it different from starch?
Glycogen, commonly known as animal starch, is a type of carbohydrate found solely in animals. It is made up of polysaccharides. Glycogen and starch are the two primary sources of glucose in humans....
Classify the following into monosaccharides and disaccharides. Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose
2-deoxyribose, galactose, ribose, and fructose are monosaccharides. Lactose and maltose are two disaccharides.