TAP CHi KHOA HOC DHSP TPHCM s6 3(68) nam 2015 |̂ MOT SO BIEN PHAP NANG CAO NANG LlTC GIAI BAI TOAN DOT CHAY CAC HOfP CHAT HUtJ CO NGUYEN HLfU TAI" TOM TAT Bdi todn dot chdy cdc hgp chdt hint ca khd ph[.]
TAP CHi KHOA HOC DHSP TPHCM s6 3(68) nam 2015 ^| MOT SO BIEN PHAP NANG CAO NANG LlTC GIAI BAI TOAN DOT CHAY CAC HOfP CHAT HUtJ CO NGUYEN HLfU TAI" TOM TAT Bdi todn dot chdy cdc hgp chdt hint ca khd bien chuang trinh Hoa hgc thong De giiip hgc sinh gidi quyet bai todn ndy chung toi dua mgt sd bien phdp ndng cao ndng Igc lap edng thirc va phuang trinh hoa hgc, dong thdi qua giup hge sinh co khd ndng dua nhirng moi tuang quan giita cdc chdt v&i cdc thudt todn Irong phdn img ddt chdy cdc hgp chdt huu ca Tir khda: bai todn ddt chdy, hpp ehdt hdu co, cdng thuc hda hpc, phuang trinh hda hpc ABSTRACT Some measures to improve students* ability in solving the problem of burning organic compounds The problem of burning organic compounds is quite common in high school's general chemistry In order to help students solve the problem, several measures lo improve students' ability in building formulas and chemical equations are proposed, simultaneously, learners can find out correlations between substances and algorithms the burning of organic compounds Keywords: the burning problem, organic compound, chemical formulas, chemical equations Bat v4n 6k Qua thyc td giang day, chung tdi nhdn thay giai bai todn ddt chay cac hpp chdt huu CO, rat nhieu hpc sinh khdng phdt hidn mdi lien he giua eae chat vdi du lieu cda dd bai ndn thudng dat qua nhieu an vd dan ddn bd tdc khdng gidi dupe bdi toan Nhung bdi todn ddt chdy cac hop chat huu ca thudng cd cac dac didm chung, Id; Cd thd sd dyng cung mpt edng thuc, edng mpt phuang trinh hda hpe Id ed thd giai dupe de ddng Cau true cua ndng lyc giai bdi todn dot chdy edc hpp chat hdu co bao gom; Ndng lyc lap cdng thuc phdn td eac hpp chdt huu co, ndng luc lap phuang trlnh hda hpc ciia phdn dng ddt chay ede hpp ehdt hdu co, ndng lyc xdy dung edc cdng thde tinh todn lidn quan den ede ehdt tu phuong trinh hda hpc cua phdn dng ddt ehay Hidn nay, rdt it tdi lieu nghidn euu chuydn sdu vd vdn dd nay; chinh vi vdy chung tdi da dua m^t sd bien phdp nang cao nang luc giai bai todn ddt ehdy ede hop chdt huu eo, nhdm giup cde em hpe sinh gidi quyet eae bai todn mpt each nhanh ban ddng thdi ren luyen ndng lue phat hidn vd gidi quydt vdn dd, td giup cdc em cang tu tin vd ydu thich vide gidi toan hda hoe * ThS, Trubrg Ti^u hpc, Trung hpc ca sd v^ Trung hpc ph6 th6ng NgO Thd-i Nhi^m; Email tainguyen0406@gmail.com 106 TAP CHi KHOA HOC DHSP TPHCM NguySn BUu Tai Mot so bif n phap nang cao ndng lyc giai bai toan dot chay cac hop chat hihi ccr 2.1 Giup hgc sinh ndm vimg each Igp cdng thttc phan tir cda cdc hpp chdt hiru cff Cong thiic phan tii cua hgp chat huu co bieu thi so lugng nguyen tii ciia mdi nguyen to phan tii Dl lap cong thuc phan tu chung cua cac hgp chat him co cSn CO nhieu thong tin Trong do, co nhimg thong tin hien thi r6 rang co thi nhan thiic dugc nhu phin nguyen t6, s6 lugng nguyen tir cua m6i nguyen t6, ben canh CO nhimg thong tin doi hoi hgc sinh phai co nang luc phat hien vjn dl moi nhan thiic dugc nhu so lien ket Tt, so vong Viec lap dugc cong thuc phan tir chung ciia cac hgp chat hiiu eg se giiip cho hgc sinh vilt dugc phuang trinh hoa hgc ciia phan ling dit chay 2.1.1 Cdch lap cdng thtrc phdn tir ciia cdc hidrocacbon a Cdch l&p cdng thirc phdn tie cda ankan * Cdch Gia sii phan til ankan gIm n nguyen tu C T6ng s6 h6a tri cua C la 4n, so hoa hrj ciia C dung dl lien kit giiia C vol la 2(n-l) vi co (n-1) lien kit C-C S6 hoa tri cua cacbon diing de lien kit voi hidro la 4n - 2(n-l) = 2n+2 Vay cong thirc phan tu chung cua ankan la C„H2„+2 (n > 1) * Cdch Budc I Viet cong thiic phan tit cua mgt vai chat kl tilp metan bjng each them mgt ho§c nhilu nhom CHj, thi dy CH, hay HjCHj, CjHj hay H2CH2CH2, CjHg hay H2CH2CH2CH2 Budc Tim quy ludt bidn ddi sd nguyen tu C vd H day ehdt: d day Id H2(CH2)n Vay cdng thuc phan td chung eua ankan la CnH2n+2b Cach lap cdng thirc phan tu- cua cac hidrocacbon khdc ankan Buac Tim sd lien kdt TC vd vdng eua hidrocacbon Buac Tinh so nguydn tu H giam di so vdi ankan tuong ung: Dd hinh vdng (monoxicloankan) bode lidn kdt % tu ankan phai mat 2H => Hidrocacbon cd tdng sd lien ket n va vdng bdng k sd ed sd nguyen td H kem hon ankan la 2k => Cdng thuc phan tu cua hidrocacbon Id CnH2n+2-2kThidu Lap edng thde phan td chung day ddng dang cua vinyl axetilen Budc } Tim sd lidn kdt n va vdng eua hidrocacbon Day ddng dang eua vinyl axetilen la nhung hidrocacbon mach hd (tue khdng ed vdng) cd lien kdt TI phdn tu Budc Tinh sd nguydn tu H giam di so vdi ankan tuong ung Vi phan td hidrocacbon cd lidn kdt n nen sd nguyen tu H gidm di so vdi ankan tuong ung la => edng thde phan tu chung cua hidrocacbon Id CnH2n+2-6 hay CnH2n4 (n >4)- 107 TAP CHi KHOA HOC DHSP TPHCM s6 3(68) ndm 2015 2.1.2 Cdch lap cong thicc phdn tic ciia cdc hgp chdt hint ca co chiea nhom chirc Budc } Tim tdng sd lien kdt n va vdng ciia todn bp phan tu rdi lap edng thuc phan tu hidrocacbon tuong ung Ndu hpp ehdt huu eo ed k lien kdt n vd vdng thi hidrocacbon tuong dng se ed edng thuc la CnH2n+2-2kBuac Xdc djnh sd nguydn td oxi, nito, halogen de thdm vdo cdng thuc hidrocacbon vda lap Chu y: Dd dam bao hda tri eua eae nguydn td (eaebon cd hda tri bdn, hidro cd hda tri mpt, oxi cd hda tri hai, nito cd hda tri ba, halogen cd hda tri mdt), ndu thdm oxi thi khdng thay ddi sd nguyen td hidro nhung ndu thdm nito thi phdi them hidro (thi dy thdm nguydn td nito phdi them nguydn td hidro), them halogen thi phdi bdt hidro (thi dy them nguydn tu phai bdt nguyen tu hidro) Thi dg Lap edng thde phan td ehung cua cac amino axit no, mgeb hd ehua nhdm -NH2 vd nhdm -COOH phan tu Buac } Tim tdng sd lidn kdt TI va vdng eua toan bp phdn tu amino axit Vi amino axit no, mach hd nen phdn gdc eua nd khdng ed Hen ket n vd vong nhung ed lidn ket % nhdm ehuc -COOH => cdng thuc phan td hidrocacbon tuong dng la CnH2n+2-2 hay CnH2n Budc Xae dinh sd nguydn td O, N dd them vao edng thuc hidrocacbon vda lap Chu y dd ddm bdo hda tri eua eac nguydn td, ndu thdm nito thi phdi them hidro Phdn tu amino axit cd nhdm -NH2 va nhdm -COOH ndn cd nguyen td O va nguydn tu N Nhu vdy phdi thdm nguydn tu H => Cdng thdc phan tu chung cua amino axit no, mach hd chua nhdm -NH2 vd nhdm -COOH Id CnHsn+iOjN (n > 2) 2.2 Giup hgc sinh hf thong hda cdc phuong trinh hoa hgc cua phdn irng dot chdy nhirng hgp chdt hiru cff quan trgng Ban chat eua cdc bdi todn hda hpc phan Idn ddu the hien mdi quan he giua eac chat phdn ung Vide quan sat phuong trinh hda hpc cda phdn ung se gidp hpc sinh rut cdc cdng thdc tinh toan lien quan ddn cac chdt, tu giup hpc sinh gidi nhanh cac bdi tap Sau ddy la phuong trinh hda hpc cua phan ung ddt chay cdc hpp chat hdu co quan trpng 2.2.} Phuang trlnh hoa hgc cua phdn ung dot chdy cdc hidrocacbon C^H^ +(x+^O^ -^ xCO-, + ^ H^O Dot chdy ankan C,//,„, C A „ 2++( ^( ^^) ^ nCO^ + {« + \)Hfi Dot chdy xicloankan, anken C^H,,+—0,->nCO,+nh Ddt chdy ankadien ankin 108 TAP CHi KHOA HOC OHSP TPHCM NguySn Hieu Tdi C„«2„-! + ( ^ ^ ) , ->nCO, +(,n-l)H,0 Bdt chdy hidrocacbon cd Ttnhir vinyl axetilen C.,,-4 +(^^^)02 ->-nCO,+in-2)Hfi Ddt chdy ddy ddng ddng cita benzen CM2,.t + (^Y^)O, -> nCO, + (« - 3)//,0 Ddt chdy axetilen, vinyl axetilen, benzen, stiren CH, +—0, -^nCO,+-H,0 " " • - 2.2.2 Phuang trinh hoa hgc ciia phdn img ddt chdy cdc hpp chdt huu ca cd chua nhom chirc C.HO + (x + ^ - - ) , -^ xCO, + ^ H,0 ' • " CMO.N,+(_x + ^ )0,^xCO,+^H,0+-N, y f ' ' 2 ' Dot chdy ancol, ete no, dom chirc, mach C,H,,^ft + —0^^ nCO, +(n + \)H,0 Ddt chdy ancol, ete no, hai chirc, mach hd C,fl,,^,0, + ( ^ ^ ) , -> nCO, +{n + l)H,0 Ddt chdy ancol, ete no, ba chirc, mach hd CMinM + ( ^ ^ ^ ) , -^ nCO, +(n + \)Hfi Ddt chdy andehit, xeton no, dan chuc, mach ha; ancol, ete dan chuc,mgch co mgt lien ket ddi C=C C^H.fi + (^Y^)O, -> nCO, + nHfi Dot chdy andehit, xeton dan chirc, mach ha, co mdt lien kit ddi C-C: ancol, ete dan chirc, mach ha, cd mgt lien ket ba C=C hodc hai lien kit ddi C=C C,H„_,0 + (~^)0^ ~*nCO, +(n-\)Hfl Ddt chdy axit, este no, dan chirc mach hd: tgp chitc andehit - ancol no, mach C„H^fiT, + ( ^ ^ ) , -> nCO^ + nHp TAP CHi KHOA HQC DHSP TPHCM 55 ^(68) nam 2015 Bdt chdy axit, este dan chiic, mach hd, co mdt lien kit ddi C=C: andehit no, hai chirc, mach C,H„_,0, + ( ^ ^ ) , -> nCO, + (« - l)Hfi Bdt chdy amin no, dan chuc, mach hd C,H,„,N + (,^)0, -^„CO,_ + (.^)Hfi+^N, Dot chdy amino axit no, mgch ha, co nhom -NH2 vd nhom -COOH CA,^AN +( ^ n ^ nCO, +(^)H,0+^N, Ddt chdy mudi ciia axit cacboxylic, thi dii: C^2n+iCOONa 2C,Hj,,,C00Na + (3ô +1)02 ->ã Na.CO, + (2« + ])C02 + (In + l)Hfi 2.3 Xdy dtpig mgt so cdng thirc tinh todn quan trgng lien quan den cdc chdt tie phieffng trinh hda hgc cua phan teng dot chay cdc hgp chdt hieu cff (1) Tit phuang trinh hoa hgc cua phan img d6t chay hgp chit huu eg A chiia C,H,0,N: CM ON, +(;t + ^ - - ) , -^xCO, • ' • ' ' ' ' ta eg cac cong thiic: n,.Q +^H,0+-N, ' ' , 2nf,f, (a)so nguyen tu cacbon = —'-, so nguyen tii hidro = —'— «., "A < 2n„ so nguyen tu mta = nCO, + (n - \)Hfi C„Hi,-fit + ^^""^^O; ->ã "CO2 + (ô - 2)^20 tec6Ko^=-H^o 2.^ Giup A(?c sinh ndm vO-ng cdc budc gidi mgt bdi todn ddt chdy cdc hgp chat hieu cff Giai bai toan dot chay cac hgp chit hiru co c6 the theo trinh tu buac: Budc Tim cong thirc phan tir ciia cac hgp chat hiru eg dem dgt chay tir viec phara tich dac dilm clu tag ciia chiing Buac Viet phuang trinh hoa hgc cua cac phan irng Budc Van dung cac cgng thirc tinh tgan phii hgp dl thuc hien y6u cau cua bai toan Mgt s6 bai tap ap dyng Bai tap H6n hgp M gom andehit no, don chirc X va axit cacbgxylic dan chiic Y eg s6 lien kit Ji nhg hon 3, diu mach ho Dit chay hit x moi M, cin vira dii 0,22 moi O2, thu 111 TAP CHi KHOA HOC BHSP TPHCM Sd 3(68) nim 2015 dugc 0,18 moi CO; va 0,15 moi HjO Tinh phin phin tram s6 moi cua X hon hgp M Giai: Budc I Ddt cdng thirc phdn tie ciia cdc hap chdt hiru ca Andehit no, don chiic mach ho X co dang C„H2„0 (n > 1) Axit Y don chiic, mach ho co s6 lien kit it < 3, co dang C„H2„02 (n > 1) ho}c C„H2„.202(n>3) _ Vi dit chay hSn hgp gom andehit X va axit Y cho n„,„ < «, „, ,trong andehit X cho n^„_ = n„j, => axit Y phai co dang C„H2„.202 Buac Viit phuang trinh hda hgc ciia cdc phdn irng CH,0 + ( ^ ^ ) , ->nCO,+nH,0 C.Hi,-20i + ^^""'^02 -> "CO, + (n - \)Hfi Budc Xdy dung cdc cdng thuc tinh todn lien quan den cdc chdt cdn tim Tir phuong trinh hoa hgc cua phan img dot chay, ta co: "ax,iY= ",„, -"«,„ =0,18-0,15 = 0,03 (moi) Dua vao su bao toan nguyen to oxi, ta co: HQ Lrong andehit X •*" " Irong axit V + tlQ oxiphanung^no CO, "*" " O H^O = ^ riandtfhil don chirc X "*" 2na.xit Y "*" 2n(,^ ~ 2n(.^,_ + n „ ^ „ => n.„d,H„ ,„„ ,i, X = 2.0,18 + 0,15 - 2.0,03 - 2.0,22 = 0,01 (moi) - ^ 0/ - 0,01.100 , - > /•n™dch,.trongM-^J^jy:p^^-25 Bdi tgp (Di thi TSBH ndm 2011) Dot chay hoan toan 3,42 gam hon hcrp axit acrylic, vinyl axetat, metyl acrylat vk axit oleic, roi hap thu to^n bg san pham chay vao dung djch Ca(0H)2 (du) Sau phan img thu dugc 18 gam ket tiia va dung dich X Khoi lugng X so v6i khoi lugng dung djch Ca(0H)2 ban diu d3 thay doi nhu the nao? A Giam 7,38 gam B TSng 2,70 gam C, Tang 7,92 gam D Giam 7,74 gam GidL Budc Dgt cdng thiic phdn tir chung ciia cdc hgp chdt hint ca Axit acrylic CH2=CHC00H, vinyl axetat CH3COOCH=CH2, metyl acrylat CH2=CHCOOCH3, axit oleic CH3-[CH2],-CH=CH-[CH2]7-COOH diu chiia C, H vJ nguyen tit oxi, diu co lien kit Tt phan tir Vi vay co the dat cong thirc phan tii chung ciia chung la C„H2„.202 112 TAP CHl KHOA HOC DHSP TPHCM Nguyin Huu Tdi Budc Viit phircmg trinh hda hgc cita cdc phdn img C„H„ ,0, + ^^"~'*0,-»>iCa - - +(n-l)H,0 CO, + Ca(OH), -> CflCOj i + / / , Birdc Xdy dimg cdc cdng thirc tinh todn lien quan den cdc chdt cdn tim + Tir phucmg trinh hoa hgc ciia cac phan img ta co: 18 "co = «< „ra = = 0,18 (mol) '''"> 100 3 =>3,42+-n„^o.32 = 0,18.44 + n„^o.18 => n„.„ = 0,15 (mol) + Khoi lugng dung dich X tang hay giam so voi dung dich Ca(0H)2 ban diu tiiy thugc vao tong khIi lugng CO2, H2O them vao dung dich va khIi lugng ket tiia CaCOs tach ">,o, +n