CBSE NCERT Solutions for Class 12 Chemistry Chapter 1

Cbse Ncert Solutions For Class 12 Chemistry Chapter 1-Free PDF

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Class XII CBSE Chemistry The Solid State,Potassium sulphate Ionic solid. Potassium sulphate has 2K and SO 4 It consists of positively charged cations and. negatively charged anion When an ionic solid is dissolved in water the cations and. anions are separated and become free to move about in the water allowing the. solution to conduct electrical current,Tin Metallic solid. Metallic solids are solids composed of metal atoms that are held together by. metallic bonds These bonds are like huge molecular orbitals that span across the. whole solid This means the electrons in metallic solids are delocalized. Benzene Molecular non polar solid, Non polar molecular solid In these solids the atoms or molecules are held by weak. dispersion forces or London forces These solids are soft and non conductors of. electricity,Urea Polar molecular solid, Polar molecular solids In these types of solids the geometry is in such a way that. one side has a negative charge and the other has a positive charge The force. between them is a dipole dipole force of attraction The melting and boiling points. of these solids are higher than non polar molecular solids but still relatively low. Ammonia Polar molecular solid, Polar Molecular Solids In these types of solids the geometry is in such a way that.
one side has a negative charge and the other has a positive charge The force. between them is a dipole dipole force of attraction The melting and boiling points. of these solids are higher than non polar molecular solids but still relatively low. Water Hydrogen bonded molecular solid, Hydrogen bonded molecular solids contain polar covalent bonds between H and. F O or N atoms Strong hydrogen bonding binds molecules of such solids like H2 O. They are non conductors of electricity and are volatile liquids or soft solids under. room temperature and pressure,Zinc sulphide Ionic solid. Zinc sulphide has positively charged cation Zn 2 and negatively charged anion. S 2 When ionic solid is dissolved in water the cations and the anions get. separated and become free to move in the water allowing the solution to conduct. electrical current, Practice more on The Solid State Page 2 www embibe com. Class XII CBSE Chemistry The Solid State, Metallic solids are solids composed of metal atoms that are held together by. metallic bonds These bonds are like huge molecular orbitals that span across the. whole solid This means the electrons in metallic solids are delocalized. Graphite Covalent or network solid, A network solid or covalent network solid is a type of solid in which the atoms.
present are bonded by covalent bonds in a continuous network that extends. throughout the material In a network solid there are no individual molecules and. the entire crystal or amorphous solid may be considered a macromolecule. Rubidium Metallic solid,Argon Non polar molecular solid. Non polar molecular solids In these solids the atoms or molecules are held. together by weak dispersion forces or London forces These solids are soft and non. conductors of electricity,Silicon carbide Covalent or network solid. Silicon carbide makes a network structure by covalent bonds. 1 7 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. Solid A is hard and acts as an electrical insulator in molten as well as solid state It. can be either hydrogen bonded molecular solid or covalent solid Since it has a high. melting point it is a covalent or network solid Covalent Network solid examples. are diamond and quartz SiO2, 1 8 Ionic solids conduct electricity in the molten state but not in a solid state Explain. Ionic solids dissociate to give free ions and electricity is conducted by ions in an. aqueous or molten state In the solid state ions are held together by strong. electrostatic forces and are not free to move So it is a bad conductor of electricity. in the solid state, 1 9 What type of solids are electrical conductors malleable and ductile. Metallic solids are solids composed of metal atoms that are held together by. metallic bonds These bonds are like huge molecular orbitals that span across the. whole solid This means the electrons in metallic solids are delocalized So they. are a good conductor of electricity and they are malleable and ductile. 1 10 Give the significance of a lattice point, Practice more on The Solid State Page 3 www embibe com.
Class XII CBSE Chemistry The Solid State, The space lattice is strictly a geometrical concept and represents a three. dimensional translational repetition of the centres of the units of pattern in the. crystal The unit of the pattern can be anything i In metals or inert gases each. lattice point may represent the position of each atom ii In a crystal of methane. each lattice point may represent the centre of a methane molecule iii In ionic. crystals the lattice points may represent ions or ion pairs. 1 11 Name the parameters that characterise a unit cell. A unit cell is characterized by the following six parameters. i The three edges dimensions a b and c, ii Angles between the edges between edges b and c between edges a. and c and between edges a and b,1 12 Distinguish between. i Hexagonal and monoclinic unit cells,ii Face centred and end centred unit cells. i Hexagonal unit cell,For a hexagonal unit cell,System Axial angles Diagram.
Hexagonal a b c, Practice more on The Solid State Page 4 www embibe com. Class XII CBSE Chemistry The Solid State,The hexagonal closest packed. structure is described by a,hexagonal unit cell which has a. diamond shaped or hexagonal,base with sides of equal length. a b The base is,perpendicular to the longest side,length c of the unit cell An atom.
is centred on each corner of the,unit cell An atom is also centred. inside the unit cell and two atoms,whose centre lies outside the unit. cell extended into the unit cell,Monoclini The crystal in the monoclinic. a b c 90o system is described by vectors of,c unit cell. unequal length as in the case of,the orthorhombic system These.
vectors form a rectangular prism,with a parallelogram as its base. Two pairs of vectors are therefore,perpendicular while the third pair. produces an angle other than 90,Face centred unit cell End centred unit cell. A face centred unit cell has constituent An end centred unit cell has particles at. particles which are present at the corners the corners and one at the centre of any. and one at the centre of each face two opposite faces. Practice more on The Solid State Page 5 www embibe com. Class XII CBSE Chemistry The Solid State,Total number of particles in a face. Total number of particles in an end,centred unit cell 8 1 8 6 1 2.
centred unit cell 8 1 8 1 2, 1 13 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. i An atom at the corner of a cubic unit cell is shared by eight adjacent unit. Thus 8 th portion of the atom is shared by one unit cell. ii An atom at the body centre of a cubic unit cell is not shared by its. neighbouring unit cell The atom is therefore only part of the unit cell in. which it is present i e its contribution to the unit cell is 1. 1 14 What is the two dimensional coordination number of a molecule in square close. packed layer, A molecule is in contact with four of its neighbours in a two dimensional square. close packed layer Therefore a molecule s two dimensional coordination number. in a close packed square layer is 4, 1 15 A compound forms a hexagonal close packed structure What is the total number. of voids in 0 5 mol of it How many of these are tetrahedral voids. Number of atoms in 1 mole of close packed structure NA 6 022 1023. Practice more on The Solid State Page 6 www embibe com. Class XII CBSE Chemistry The Solid State, Number of atoms in 0 5 moles of close packed structure 0 5 6 022 1023. 3 011 1023, Therefore number of octahedral voids number of atoms per unit cell.
3 011 1023, And number of tetrahedral voids twice the number of atoms per unit cell. 2 3 011 1023 6 022 1023, Therefore total number of voids octahedral voids tetrahedral voids. 3 011 1023 6 022 1023 9 033 1023, 1 16 A compound is formed by two elements M and N The element N forms ccp and. atoms of M occupy 1 3 of tetrahedral voids What is the formula of the. Suppose the atoms of the elements N form the ccp lattice. The amount of tetrahedral voids generated here is twice that of number of atoms of. the element N i e 2N, The Question states that the atoms of element M occupy one third of the tetrahedral. The number of atoms of M is equal to 2N 1 3 2 3 of the number of atoms. Thus the formula of the compound is M2 3 N M2 N3, 1 17 Which of the following lattices has the highest packing efficiency.
i simple cubic,ii body centred cubic and,iii hexagonal close packed lattice. The packing efficiency of hexagonal close packing is. Volume of the atoms 6 3 r 3,Valume of unit cell 24 2 r 2 3 2. volume occupid by atoms unit cell, The packing efficiencies of simple cubic volume of unit cell. a 3 2r 3 3 8 r3, Practice more on The Solid State Page 7 www embibe com. Class XII CBSE Chemistry The Solid State, The packing efficiencies of body centred cubic lattices 4 4 4r.
1 18 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. Given Density of the element d 2 7 103 g m 3,Molar mass M 2 7 10 2 kg mol 2. Edge length a 405 pm 405 10 12 meter 4 05 10 10 meter. It is known that Avogadro number NA 6 022 1023 mol 1. To find The nature of the cubic unit cell, For this we should know the number of atoms per unit cell N. Using the formula,N d a3 NA M, 2 7 103 kgm 3 4 05 10 10 m 3 6 022 1023 mol 1 2 7 10 2 kg mol 1. N 4 implies that four atoms of the element are present per unit cell Therefore. the nature of the cubic unit cell is face centred cubic fcc or cubic close packed. 1 19 What type of defect can arise when a solid is heated Which physical property is. affected by it and in what way, When a solid is heated there will be a vacancy defect If some of the lattice sites. are vacant a solid crystal is said to have a vacancy defect Vacancy deficiency. results in a decrease in solid density, 1 20 What type of stoichiometric defect is shown by.
Practice more on The Solid State Page 8 www embibe com. Class XII CBSE Chemistry The Solid State,i ZnS shows Frenkel defect. When an ion is missing from its correct lattice sites causing a vacancy or a. hole and occupies an interstitial site electrical neutrality as well as the. stoichiometry of the compounds are maintained Since cations are smaller. it is more common to find the cations occupying interstitial sites This type. of defect is present in ionic compounds which have a low coordination. number a large difference in the size of cation and anions compounds. having highly polarising cation and easily polarisable anion. Red ball indicate Z 2 ion,Blue ball indicate S 2 ion. ii AgBr shows both Frenkel defect and Schottky defect. AgBr is an ionic crystal having Ag Br When an equal number of cations. and anions are missing from their lattice it creates a Schottky defect. This type of defect is shown by highly ionic compounds which have high. coordination number and a small difference in the sizes of cations and. Practice more on The Solid State Page 9 www embibe com. Class XII CBSE Chemistry The Solid State,Red ball indicate Ag ion. Blue ball indicate Br ion, Frenkel defect This type of defect is present in ionic compounds which. have low coordination number larger difference in the size of cation and. anions and compounds having highly polarising cation and easily. polarisable anion,Red ball indicates Ag ion,Blue ball indicates Br ion.
1 21 Explain how vacancies are introduced in an ionic solid when a cation of higher. valence is added as an impurity in it, Let us take an example of NaCl doped with SrCl impurity When SrCl2 is added to. solid NaCl as an impurity two Na ions will be replaced and one of the sites will. be occupied by Sr 2 while the other will remain vacant Thus we can say that when. a cation of higher valance is added as an impurity to an ionic solid two or more. cations of lower valency are replaced by a cation of higher valence to maintain. electrical neutrality Therefore some cationic vacancies are created. Practice more on The Solid State Page 10 www embibe com. Class XII CBSE Chemistry The Solid State, 1 22 Ionic solids which have anionic vacancies due to metal excess defect develop. colour Explain with the help of a suitable example. Taking the example of NaCl when NaCl is heated in an atmosphere of sodium. vapours the sodium atoms get deposited on the surface of the crystal and the. chloride ions from the crystal diffuse to the surface to form NaCl with the deposited. Na atoms During this process the Na atoms on the surface lose electrons to form. Na ions and the released electrons diffuse into the crystal to occupy the vacant. anionic sites These electrons get excited by absorbing energy from the visible light. and impart yellow colour to the crystals The colour develops because of the. Class XII CBSE Chemistry The Solid State Practice more on The Solid State Page 1 www embibe com CBSE NCERT Solutions for Class 12 Chemistry Chapter 1 Back of Chapter Questions 1 1 Why are solids rigid Solution The particles of solids are close to each other and they are tightly bonded having

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