Written as per the revised syllabus prescribed by the Maharashtra State Board of Secondary and Higher Secondary Education, Pune.

Transcription

1 Writtn as pr th rvisd syllabus prscribd by th Maharashtra Stat Board of Scondary and Highr Scondary Education, Pun. Prfct Chmistry I STD. XII Sci. Salint Faturs Exhaustiv covrag of syllabus in Qustion Answr Format. Covrs answrs to all Txtual Qustions, Intxt Qustions and Numricals. Includs marking schm for Board Qustions from 2013 to Covrs rlvant NCERT Qustions. Includs Board Qustion Paprs of 2016 and Quick Rviw for instant rvision and summary of th chaptr. Exrcis, Multipl Choic Qustions and Topic Tst at th nd of ach chaptr for ffctiv prparation. Important inclusions: NCERT Cornr and Apply Your Knowldg. Rlvant NCERT Qustions and Answrs for xtra practic ar availabl in downloadabl PDF format at Printd at: Dainik Saamana, Navi Mumbai Targt Publications Pvt. Ltd. No part of this book may b rproducd or transmittd in any form or by any mans, C.D. ROM/Audio Vido Casstts or lctronic, mchanical including photocopying; rcording or by any information storag and rtrival systm without prmission in writing from th Publishr _12260_JUP P.O. No.87724

2 Indx Ch. No. Chaptr Nam Marks Pag No. 1 Solid Stat Solutions and Colligativ Proprtis Chmical Thrmodynamics and Enrgtics Elctrochmistry Chmical Kintics Gnral Principls and Procsss of Isolation of Elmnts pblock Elmnts Board Qustion Papr - March Board Qustion Papr - July Board Qustion Papr - March Board Qustion Papr - July Logarithmic Tabl 532 Modrn Priodic Tabl 536 'Chaptrs 8 to 16 ar a part of Std. XII: Prfct Chmistry - II' Not: All th Txtual qustions ar rprsntd by * mark. All th Intxt qustions ar rprsntd by # mark.

3 01 Solid Stat Subtopics 1.0 Prominnt scintists 1.1 Introduction 1.2 Classification of solids 1.3 Classification of crystallin solids 1.4 Unit cll and two and thr dimnsional lattics 1.5 Packing in solids 1.6 Dnsity of unit clls 1.7 Packing in voids of ionic solids 1.8 Dfcts in crystal structur 1.9 Elctrical proprtis 1.10 Magntic proprtis 1.0 Prominnt scintists Scintists William Hnry Bragg ( ) (British physicist, chmist and mathmatician) William Lipscomb ( ) (Amrican inorganic and organic chmist) Isablla Karl (1921) (Amrican X-ray crystallographr) Contributions i. Drivd th Bragg quation n = 2d sin to xplain why clavag of crystal rflct x-ray bam of wavlngth at an angl. ii. Shard th Nobl Priz in 1915 with his son William Lawrnc Bragg for dtrmining crystal structurs of NaCl, ZnS and Diamond. i. Dtrmind structur of boron hydrid using tchniqu of x-ray crystallography. ii. Rcivd th Nobl Priz in chmistry in 1976 for his work on structur and bonding of boron hydrid and its drivativs. i. Dvlopd mthod for dtrmining th molcular structur by x-ray diffraction. ii. Workd on crystallography of matrials in th fild of organic chmistry and biochmistry. 1.1 Introduction Q.1. Undr what conditions dos a substanc xist in solid stat? Ans: i. Mattr can xist in thr stats namly, solid, liquid and gas. Undr a givn st of conditions of tmpratur and prssur, th most stabl stat of a substanc dpnds upon th nt ffct of two opposing forcs: intrmolcular forcs and thrmal nrgy. ii. Intrmolcular forcs tnd to kp th constitunt particls (atoms, ions or molculs) closr, whras thrmal nrgy tnds to kp thm apart by making thm mov fastr. iii. Th comptition btwn molcular intraction nrgy du to intrmolcular forcs and thrmal nrgy dtrmins whthr a givn substanc undr a givn st of condition is a gas, a liquid or a solid. iv. At sufficintly low tmpratur, th thrmal nrgy is low and molcular forcs ar vry strong. As a rsult, th intrmolcular forcs kp th constitunts so clos that thy cling to on anothr and occupy fixd positions and th substanc xists in solid stat. 1

4 Std. XII Sci.: Prfct Chmistry - I Q.2. Explain th convrsion of stats of mattr from on form to th othr with th changing conditions of tmpratur and prssur. Ans: i. Mattr can b changd from on stat to anothr by changing tmpratur and prssur. ii. Mattr xists in solid stat at rlativly lowr tmpratur. iii. Whn th solid is hatd to its mlting point, thrmal nrgy ovrcoms th intrmolcular forcs of attraction. Th solid mlts and changs into liquid. Th liquid on hating to its boiling point vapourizs to form gas. iv. Whn gass ar coold undr high prssur, thy condns into liquid stat. Th liquid thus formd on cooling changs into solid. hat hat Solid stat Liquid stat Gasous stat 2 cool cool Q.3. Dfin a solid. Ans: A solid is dfind as that form of mattr which posssss rigidity and hnc posssss a dfinit shap and a dfinit volum. *Q.4. Giv charactristics of solid stat. Ans: Th solid stat is charactrizd by th following proprtis: i. Solids hav dfinit mass, volum, shap and dnsity. Usually, th dnsity of solid stat is gratr than th dnsity of liquid and gasous stat. Watr and mrcury ar xcptions. Th dnsity of ic (solid stat of watr) is lowr than th dnsity of liquid stat of watr. Th dnsity of mrcury (which xists in liquid stat) is vry high (13.6 g ml 1 ). ii. Solids ar usually hard, incomprssibl and rigid. Som solids lik sodium, potassium and phosphorous ar xcptions; thy ar soft. Solids cannot b comprssd bcaus th intrmolcular distanc of sparation btwn nighbouring molculs is vry small. iii. In a solid stat, intrmolcular forcs of attraction btwn th constitunt particls ar strongr than iv. thos prsnt in liquid and gasous stats. All pur solids hav charactristic mlting points which dpnd on th xtnt of intrmolcular forcs prsnt in th solid stat. Strongr th intrmolcular forcs of attraction, highr is th mlting point of th solid. Wakr th intrmolcular forcs of attraction, th lowr is its mlting point. Hnc, dpnding on th intrmolcular forcs of attraction, mlting points of th diffrnt solids rang from almost absolut zro (hlium) to a fw thousand Klvin (diamond). v. Thintrmolcular forcs of attraction hold th constitunt particls of th solids tightly. Hnc th particls cannot changthir positions and rmain stationary at on position. Thrfor, solids cannot flow lik liquids. Chck Your Grasp Why do solids hav a dfinit volum? (NCERT) Th intrmolcular forcs btwn th constitunt particls (atoms, ions or molculs) of solid stat ar vry strong. Thrfor, thy ar strongly hld at fixd positions and particls cannot sparat from on anothr. Hnc, solids hav a dfinit volum. 1.2 Classification of solids *Q.5. Giv th classification of solids. Ans: Solids ar classifid as crystallin and amorphous on th basis of th prsnc or absnc of ordrly arrangmnt of thir constitunt particls (atoms, ions or molculs). i. Crystallin solids: A crystallin solid is a homognous solid in which th constitunt particls (atoms, ions or molculs) ar arrangd in a dfinit rpating pattrn. Crystallin solids ar furthr classifid as: a. Isomorphous form: 1. Two or mor substancs having th sam crystal structur ar said to b isomorphous (iso-sam, morphous-form) and th phnomnon is calld isomorphism. 2. Th constitunt atoms of isomorphous substancs ar in th sam atomic ratio. Th molcular formula and chmical proprtis of th isomorphous substancs ar similar.

5 Chaptr 01: Solid Stat 3. Following ar som xampls of pairs of isomorphous substancs and thir atomic ratios: Sr. no. Isomorphous substancs Atomic ratios Sr. no. Isomorphous substancs Atomic ratios i. NaF and MgO 1:1 iii. K 2 SO 4 and K 2 SO 4 2:1:4 ii. NaNO 3 and CaCO 3 1:1:3 iv. Cr 2 O 3 and F 2 O 3 2:3 4. Som substancs ar not isomorphous vn though thy hav sam atomic ratio, similar molcular formula and similar chmical proprtis. This is bcaus thy hav diffrnt crystal structurs. g. Sodium chlorid (NaCl) and potassium chlorid (KCl) b. Polymorphous / Allotropic form: 1. A singl substanc that crystalliss in two or mor forms undr diffrnt conditions is calld polymorphous (poly-many, morphous-form) and th phnomnon is calld polymorphism. 2. Th polymorphic forms ar also calld allotropic forms. g. i. Diamond, graphit and fullrn ar thr polymorphic forms of carbon. ii. Rhombic sulphur and monoclinic sulphur ar two allotrops of sulphur. iii. Silicon dioxid and calcium carbonat also hav allotrops. ii. Amorphous solids / Psudo solids / Supr coold liquids: Th substancs that appar lik solids but do not hav wll dvlopd prfctly ordrd crystallin structur ar calld amorphous (no form) solids. g. Tar, glass, plastic, rubbr, buttr, tc. *Q.6. Explain crystallin solids and amorphous solids. Ans: i. Crystallin solids: a. A crystallin solid usually consists of a larg numbr of small crystals, ach of thm having a dfinit charactristic gomtrical shap. Ths tiny crystals ar calld unit clls. b. A unit cll is a basic rpating structural unit of a crystallin solid. c. Crystallin solids hav long rang ordr which mans that thr is a rgular pattrn of arrangmnt of particls (atoms, ions or molculs) which rpats itslf priodically ovr th ntir crystal. g. Sodium chlorid and quartz Crystallin quartz ii. Amorphous solids: a. Th arrangmnt of constitunt particls (atoms, molculs or ions) in amorphous solids has only short rang ordr. b. In such an arrangmnt, a rgular and priodically rpating pattrn is obsrvd ovr short distancs only. c. Such portions ar scattrd and in btwn, arrangmnt is disordrd. g. glass, rubbr, plastics and amorphous silicon. Amorphous quartz glass Q.7. Dfin th trm anisotropy. [Mar 17] Ans: Anisotropy: Th ability of crystallin solids to chang valus of physical proprtis whn masurd in diffrnt dirctions is calld anisotropy. [Dfinition 1 Mark] 3

6 Std. XII Sci.: Prfct Chmistry - I #Q.8. Explain th trms anisotropy and unit cll. Ans: i. Anisotropy: a. Th ability of crystallin solids to chang valus of physical proprtis whn masurd in diffrnt dirctions is calld anisotropy. b. For crystallin solids, th physical proprtis lik rfractiv indx, lctrical conductanc, dilctric constant, tc., ar diffrnt in diffrnt dirctions. As th dirction changs (MN, OP, QR, tc.), th composition of th mdium changs. This rsults in anisotropy. Q O P 4 ii. Unit cll: a. Crystallin solids ar aggrgats of many small, tiny crystals. Ths tiny crystals ar calld unit clls. b. A unit cll is a basic rpating structural unit of a crystallin solid. Q.9. *Distinguish btwn crystallin solids and amorphous solids. Giv xampls. OR Distinguish btwn crystallin solids and amorphous solids. [Mar 13, 14, 17] Ans: Proprty Crystallin solids Amorphous solids i. Shap Thy hav dfinit charactristic gomtrical shap du to th ordrly rgular long rang Thy hav irrgular shap and lack charactristic gomtrical shap du arrangmnt of constitunt particls. to th short rang ordrly ii. Mlting point Thy hav sharp and charactristic mlting point. arrangmnt of constitunt particls. Thy do not hav sharp mlting point. Thy gradually softn ovr a rang of tmpratur. iii. Clavag proprty Whn cut with a sharp dgd tool, thy split into two pics and th nwly gnratd surfacs ar plain and smooth. Whn cut with a sharp dgd tool, thy cut into two pics with irrgular surfacs. iv. Hat of fusion Thy hav a dfinit and charactristic hat of fusion. Thy do not hav dfinit hat of fusion. v. Anisotropy Thy ar anisotropic, i.., hav diffrnt Thy ar isotropic, i.., hav sam physical proprtis in diffrnt dirction. physical proprtis in all dirctions. vi. Natur Thy ar tru solids. Thy ar psudo solids or supr vii. Ordr in arrangmnt of constitunt particls g. M Particl Particl 2 Anisotropy in crystallin solid Thy hav long rang ordr. R coold liquids. Thy hav only short rang ordr. Coppr, silvr, iron, zinc sulphid, common Glass, rubbr, plastics, tc. salt, potassium nitrat, tc. [Any four distinguishing points ½ Mark ach] N

7 Chaptr 01: Solid Stat Q.10. Classify th following as amorphous or crystallin solids: Polyurthan, naphthaln, bnzoic acid, tflon, potassium nitrat, cllophan, polyvinyl chlorid, fibr glass, coppr. (NCERT) Ans: Amorphous solids: Polyurthan, tflon, cllophan, polyvinyl chlorid, fibr glass. Crystallin solids: Bnzoic acid, potassium nitrat, coppr, naphthaln. *Q.11. What is a glass? Ans: i. Silicon dioxid is fusd with sodium oxid and boron oxid to form an optically transparnt matrial known as glass. Th colour of glass is du to addition of a trac amount of transition mtal oxid. ii. Diffrnt typs of glass ar manufacturd by changing its composition. Almost ight hundrd diffrnt typs of glasss ar manufacturd. iii. Quartz glass is obtaind from only silicon dioxid. iv. Pyrx glass is obtaind by fusing togthr 60 to 80% SiO 2, 10 to 25% B 2 O 3 and rmaining amount of Al 2 O 3. Q.12. Giv th compositions of diffrnt typs of glass. Ans: i. Quartz glass is obtaind from only silicon dioxid. ii. Pyrx glass is obtaind by fusing togthr 60 to 80 % SiO 2, 10 to 25% B 2 O 3 and rmaining amount of Al 2 O 3. iii. Whn 75% SiO 2 is fusd with 15% Na 2 O and 10% CaO, sodalim glass is obtaind. iv. Rd glass contains trac amount of gold and coppr. Yllow glass contains UO 2. v. Blu glass contains CoO or CuO. Grn glass contains F 2 O 3 or CuO. Q.13. Why is glass considrd a supr coold liquid? (NCERT) Ans: Glass is an amorphous solid. Ths amorphous solids do not hav rgular arrangmnt of constitunt particls for a longr distanc, unlik th crystallin solids. Th structur of th amorphous solids rsmbl that of liquids, du to which thy xhibit th proprty of liquids such as fluidity. Thus, ths amorphous solids tnd to float vry slowly undr gravity. Thy do not mlt at dfinit sharp mlting point, rathr gradually softn with th incras in tmpratur. Thus, glass is considrd as a psudo solid or supr coold liquid. Chck Your Grasp What maks a glass diffrnt from a solid such as quartz? Undr what conditions could quartz b convrtd into glass? (NCERT) Quartz is a crystallin solid with long rang ordr whras glass is an amorphous solid with short rang ordr. Whn quartz is hatd, it can b convrtd into glass at som tmpratur. 1.3 Classification of crystallin solids Q.14. Nam th diffrnt typs of crystallin solids on th basis of diffrnt forcs prsnt in thm. Ans: Dpnding upon th natur of intrmolcular forcs prsnt in th constitunt particls, crystallin solids ar classifid into th following four classs: i. Molcular solids ii. Ionic solids iii. Mtallic solids iv. Covalnt solids Q.15. Explain th following trms: *i. Molcular solids ii. Polar molcular solids iii. Non-polar molcular solids *iv. Hydrogn bondd molcular solids *v. Ionic solids *vi. Mtallic solids *vii. Covalnt solids Ans: i. Molcular solids: a. Molcular solids ar crystallin solids in which th constitunt particls ar molculs of th sam compound. b. Ths ar furthr subdividd into th following thr catgoris: 1. Polar molcular solids 2. Non-polar molcular solids 3. Hydrogn bondd molcular solids 5

8 Std. XII Sci.: Prfct Chmistry - I ii. iii. iv. Polar molcular solids: a. In ths crystallin solids, th constitunt particls ar covalntly bondd polar molculs. b. Polar molculs possss prmannt dipol momnt and in solid stat thy ar hld togthr by strong dipol-dipol intraction. c. Thr is a sparation of positiv and ngativ chargs bcaus of th polar natur of molcul. Hnc, th polar molculs arrang thmslvs in such a way that opposit chargs of th nighbouring molculs ar brought closr. Charactristics: a. Thy ar soft. b. Thy do not conduct lctricity. c. Th mlting points of th solids ar rlativly low, as th bonding is rlativly wak. g. Solid SO 2, solid NH 3 and solid HCl. Non-polar molcular solids: a. Ths crystallin solids compris of ithr atoms or molculs formd by non-polar covalnt bonds. b. In ths solids, th atoms or molculs ar hld by wak disprsion forcs or London forcs. Charactristics: a. Thy ar soft. b. Thy do not conduct lctricity. c. Thy hav vry low mlting points (lowr than polar molcular solids) and ar usually in liquid or gasous stat at room tmpratur and prssur. Iodin (I 2 ) xists in solid stat vn at room tmpratur. g. Non-polar molculs lik CO 2, H 2, Cl 2, CH 4 and wakly polar molculs lik CO and othr hydrocarbons form non-polar molcular solids at rlativly lowr tmpraturs. Hydrogn bondd molcular solids: a. Ths crystallin solids consist of hydrogn atom covalntly bondd to strongly lctrongativ atom lik oxygn, nitrogn or fluorin. b. In ths molculs, th hydrogn atoms acquir additional positiv charg and form additional bond with strongly lctrongativ atoms in th vicinity. This additional bond is calld hydrogn bond. Charactristics: a. Thy do not conduct lctricity. b. Ths solids xist as liquids or gass at room tmpratur and prssur. c. On cooling, th liquids solidify. g. H 2 O, NH 3. 6 v. Ionic Solids: a. Ionic solids ar crystallin salts formd by th thr dimnsional arrangmnt of cations and anions bound by lctrostatic forcs. b. Two typs of lctrostatic forcs ar prsnt. On is th forc of attraction btwn th ions carrying opposit chargs. Th othr is th forc of rpulsion btwn th ions carrying sam chargs. c. Th arrangmnt of ions dpnds on following factors: 1. Sizs of th cation and anion 2. Th chargs on th ions 3. Th as of polarisability of th anion Ionic Crystal

9 Chaptr 01: Solid Stat Charactristics: a. Ths solids ar hard and brittl in natur. Thy hav high mlting and boiling points. b. Sinc th ions ar not fr to mov about, thy ar lctrical insulators (non-conductors) in th solid stat. c. Howvr, in th moltn or fusd stat or whn dissolvd in watr, th ions bcom fr to mov about and thrby conduct lctricity. d. Whn sharing forc is applid, ionic crystals distort and th crystal structur is fracturd. g. NaCl, ZnS, CuCl, tc. shar forc shar forc Distortion and Fractur of Ionic Crystal on th application of Sharing Forc vi. Mtallic solids: a. Mtallic solids ar th crystallin solids formd by atoms of th sam mtallic lmnt. b. Mtals ar ordrly collction of positiv ions (calld krnls) in th sa of dlocalisd lctrons. c. Ths lctrons ar mobil and ar vnly sprad throughout th crystal. Each mtal atom contributs on or mor lctrons towards th sa of mobil lctrons. d. Th forc of attraction btwn positivly chargd mtallic ion and ngativly chargd sa of dlocalisd lctrons is calld mtallic bond. Mtallic bonds ar strongr than ionic and covalnt bonds. Charactristics: a. Mtallic solids ar good conductors of hat and lctricity du to th prsnc of mobil lctrons. b. Mtallic solids ar toughr than othr solids du to prsnc of strong mtallic bonds. Th natur of mtallic bonds is such that any shap can b givn to th mtallic articl. c. Th mtallic solid contains svral layrs of th mtallic ions arrangd ovr on anothr. Ths layrs can slid on othr layrs. Hnc, th mtallic solids ar mallabl and ductil. Thy can b hammrd or rolld into thin shts of dsird thicknss and can b drawn into thin wirs of rquird siz. d. Alloys can b formd by fusing th mixtur of mtals. Alloys show all proprtis of mtals.. Mtallic solids posss mtallic lustr du to which th surfac appars gry or silvry. g. Th surfac of gold appars yllow whras th surfac of coppr appars rddish. Mtallic solid Positiv Mtal Ions in a Sa of Mobil Elctrons Shar forc Shar forc Sliding of th layrs of th mtallic solid (without undrgoing fractur) on th application of sharing forc 7