Chemistry
Question from maharashtra board chemistry book of 12th maharashtra board
- What are the consequences of Schottky defect? Consequences of Schottky defect : As the number of ions decreases, mass decreases. However, volume remains unchanged. Hence, the density of... 1
- What are paramagnetic substances? Give examples. Paramagnetic substances : The magnetic properties of a substance arise due to the presence of electrons. An electron while revolving around... 1
- Calculate the packing efficiency of metal crystal that has simple cubic structure. Packing efficiency of metal crystal in simple cubic lattice : Step 1 : Radius of sphere : In simple cubic unit cell, particles (spheres) are... 1
- How are the spheres arranged in first layer of simple cubic close-packed structures? How are the successive Three dimensional crystal structures are obtained by stacking of two dimensional layers. Simple cubic lattice is obtained by stacking of two... 1
- Calculate the number of atoms in fcc unit cell. Number of atoms in face-centred cubic (fcc) unit cell : In this unit cell, there are 8 atoms at 8 corners and 6 atoms at 6 face centres. Eac... 1
- Distinguish between ionic solids and molecular solids. Ionic solids are made of oppositely charged ions held by strong electrostatic forces, while molecular solids are made of molecules held by w... 1
- What are valence band and conduction band? Valence band : The atomic orbitals with filled electrons from the inner shells form valence bands, where there are no free mobile electrons s... 1
- What are ferromagnetic substances? The substances which possess Unpaired electrons and high paramagnetic character and when placed in a magnetic field are strongly attracted an... 1
- Mention two properties that are common to both hcp and ccp lattices. In hcp and ccp ciystal lattices coordination number is 12 and packing efficiency is 74%. 1
- A solid is hard, brittle and electrically nonconductor. Its melt conducts electricity. What type of solid is it? A solid crystalline electrolyte like NaCl is having above properties. NaCl is hard, brittle and electrically nonconductor. But its melt cond... 1
- The picture represents bands of MOs for Si. Label valence band, conduction band and band gap. Conduction band band gap valance band 1
- How does electrical conductivity of a semiconductor change with temperature? Why? Since the energy difference between valence band and conduction band in semiconductor is not large, the electrons from valence band can be p... 1
- What is the unit cell? Unit cell : It is the smallest repeating structural unit of a crystalline solid (or crystal lattice) which when repeated in different direct... 1
- The following pictures show population of bands for materials having different electrical properties Picture A represents metal conductor, Picture B represents insulator, Picture C represents semiconductor. 1
- Which of the three types of packing used by metals makes the most efficient use of fcc has the most efficient packing of particles while scc has the least efficient packing. 1
- What are the types of particles in each of the four main classes of crystalline solids ? In each of the four main classes of crystalline solids, the smallest constituents or particles of various solids are atoms, ions or molecule... 2
- Pb has fcc structure with edge length of unit cell 495 pm. Radius of Pb atom is Correct option is d. 175 pm 2
- A compound forms hcp structure. Number of octahedral and tetrahedral voids in 0.5 mole of substance is respectively a. 3.011×10²³, 6.022×10²³ 2
- Which of the following is not correct? a. Four spheres are involved in the formation of tetrahedral void. c. If the number of atoms is N the number of octahedral voids is 2N. 1
- The coordination number of atoms in bcc crystal lattice is a. 2 b. 4 c. 6 d. 8 correct option is d) 8 2
- In crystal lattice formed by bcc unit cell the void volume is a. 68 % b. 74 % c.32 % d. 26 % c.32 % correct option is c.32 % 2
- In Frenkel defect a. electrical neutrality of the substance is changed d. overall electical neutrality is preserved. 2
- Which of the following is n-type semiconductor? a. Pure Si b. Si doped with As c. Si doped with Ga b. Si doped with As 2
- Molecular solids are a. crystalline solids b. amorphous solids c. ionic solids d. metallic solids Answer: (a) crystalline solids Molecular solids such as ice, solid CO₂ (dry ice), iodine and naphthalene are made of molecules arranged in a... 1