kĩ thuật giải quyết nhanh gọn đề thi đại học môn hóa

K600T ThS.NGUYEN DINH DO GIAI Q U Y E T NHA XUAT B A N D A I HOC QUOC GIA HA NOI THS.NGUYIN DilMH DO GIAI Q U Y E T NHANH GON DE THI D A I HOC mon THI/ ViEN TJNHBIMH TMUAN Ha Npi NHA XUAT BAN DAI HOC QUOC GIA HA NQI Cac em hoc s i n h t h a n men De l a m t o t bai t h i D a i hoc la mong muon cua t a t ca cac em t r o n g cac mua t h i Doi v(5i m o n Hoa, day l a i la v a n de bijfc thiet I d n , v i le n o i dung de t h i Hoa t r a i dai ca ba k h o i 10; 11; 12 k h i e n k l i o i lifgrng k i e n thijfc di/cfng n h i i la ca mot b i e n trofi m e n h mong, vo t a n That ra, Hoa hoc la m o n hoc r a t nhe n h a n g ne'u cae em biet hoc c6 phqo'ng phap, v i le t a t ca phan ufng hoa hoc hay t i n h chat hoa hoc cua cac chat deu dUofc xac d i n h thee cac qui luat Do v a n de la n a m dtfOc cac qui luat t h i t a deu c6 the de dang diT doan t i n h chat hoa hoc m o t chat, hay de dang viet r a san pham phan ijfng giffa cac chat m a k h o n g can phai hoc thuoc san p h a m nhir cac em l a m tiio'ng bay lau N o i khac d i , hoc Hoa khong can phai hoc thuoc long, k h o n g can p h a i nhcr n h i e u nhiJng dieu ma chi can qua suy luan c6 the de dang n h a n r a chung (chang h a n t r o n g mot nhom A k h i d i tCf t r e n xuong difdi t h i ban k i n h nguyen tii" cac nguyen to bat buoc phai tang dan, do'n gian v i so Idp electron cua nguyen tuf cac nguyen to tang dan) Nguyen tSc hoc Hoa la the, vay neu k h o n g c6 k y t h u a t l a m b a i t h i trac nghiem khach quan t h i diem so' se k h o n g n h i i y so v(5i thiic life Do la thifc te ma bat cuf hoc sinh nao cung c6 the n h a n ra, va day c h i n h la l y ddi ciia tap sach Chuc cac em t i m thay n i e m vui t r o n g hoc tap, va n h a t la p h a i dat diftfc ket qua m y m a n n h a t t r o n g t h i cuf Tac gia Nguyin Dlnh 06 O CHLTdNG I KY THa6T Gl^l DE THI TR^C NGHIEM Mot dieu khong the phu nhan la du ndm rat chSc cac k i e n thijTc sach giao khoa, nhieu t h i sinh vSn khong the giai quyet t r o n ven cac cau hoi cac de t h i Dai hoc Mot thqc te la da so cac cau trSc nghiem ly thuyet cung nhif bai tap ma t h i sinh xem la rSc r o i , d i bi mat diem cac de t h i , hoac cac cau ma t h i sinh mii mcr hay ma ho ve hqdng giai l a i c6 the giai quyet rat tot bang phtfang phap loai triT Vay the nao la phqang phap loai trif? De de h i n h dung, h-ay xem mot v i du sau khong lien quan den Hoa hoc: Trong so cac nhiem ky long thong My tie xUa den nay, vi tong thong nhdt doc than den cud'i dai Id: A Bill Clinton B Jone F C James Buchanan D Abraham Kennedy Lincoln Dap an dung cho cau hoi t r e n la C (James Buchanan) Nhiftig ro rang, cau tra Idi khong phai xuat phat iii sii hieu biet ve than the James Buchanan, vi v i tong thong thijf 15 ciia Hop chung quoc Hoa ky la mot ten tuoi kha xa la vdri chung ta Cach lam d day la dung phqang phap loai trif: Trifdc tien loai triT B i l l Clinton v i han chiing t a nh6 hai vg chong tong thong B i l l Clinton ti/ng CO chuyen ghe tham Viet Nam (nam 2000) Tiep theo, tong thong Jone F Kennedy cung nam danh sach loai trii, vi vu am sat ong vao nam 1963 tai pho' Dallas, tieu bang Texas k h i dang cung phu nhan t h a m vieng tieu bang nay, la mot sii kien chan dong the gidi thcfi va hien c6 le khong khong biet Cuo'i cung, loai trCf not Abraham Lincoln cupc hon nhan day bait hanh ciia v i tong thong da dqcfc ghi l a i qua kha nhieu giai thoai Ro rang James Buchanan phai la sii liia chon cuo'i cung! Chung ta tiep tuc xem mot v i du c6 le gan gui hon v i du tren, va van la mot v i du khong lien quan den Hoa hoc: Hoa iCac Gidp Than hay c6 ten Hoa uac Patenotre (Pa-ta-not), Id hoa Udc cuo'i Cling nha Nguyen ky vai thuc dan Phap Hoa Uac Gidp Than dugc ky vdo nam ndo ditai day? A 194S B 1789 C 1752 D 1884 Khong dijng cong thufc doi nam duong lich sang nam am lich, ro rang phai loai trii nam 1948, v i trieu dai riEa Nguy§n ket thuc k h i vua Bao D a i tuyen bo' thoai v i , trao an kie'm cho dai dien chinh phu Viet nam dan chii cong hoa vao nam 1945 Cung nhanh chong loai trii nam 1789, v i day la nam vua Quang Trung keo quan Thang Long tieu diet quan Thanh Luc trieu dai nha N g u y i n chtfa diigc t.hie't lap, v i chi k h i Anh mcri x L f n g ngoi vua, lay nien hieu N g u y i n Hoan toan ttfctng t i i n h i f tren, N g u y i n chi c6 the bat dau tCf sau nam nien hieu Gia Long nam 1802) danh bai ducfc nha Tay Scfn, la Gia Long, md dau trieu loai trCr nSm 1752, v i trieu 1789 (Nguyen Anh len ngoi Nguyen dai nha dai nha vua, lay Vay liia chon cuo'i cung phai la D (nam 1884) Bay gid, ta bat tay vao mot v i du thuoc ve l i n h vifc Hoa hoc: Co ancol sau: CH3OH (I); CH3CH2CH2OH (II); CHsCmCHsJOH (III) TM tu tang dan nhiet soi cda ancol tren theo chieu til trdi sang phdi la: A (II); (I); (III) B (I); (III); (II) C (II); (III); (I) D (Ill); (I); (II) Se CO rat nhieu h o c sinh lung tung k h i doc v i du tren, sach giao khoa hoan toan khong de cap den nhiet s o i cua ancol dong phan, cu the d day la cac ancol C H C H C H O H va CH3CH(CH3)OH Tuy vay de dang nhan phai loai trCf A (ancol I C k h o n g the c6 n h i e t soi cao h a n ancol 3C); Cung l i do, phai loai trCr C va D, nen nhanh chong t i m dtfcJc dap an dung la B (thUc te nhiet soi cua ancol C H O H ; C H C H C H O H ; C H C H ( C H ) O H Ian luat la 64,7°C; 97,2°C va 82,3°C) Vf du sau day la mot dien hinh ro net cho viec sijf dung phucfng phap loai tni: Cho bot Fe vdo dung dich gSm AgNOs vd Cu(N03)2 Sau cac phan ring xdy hoan toan, thu dugc dung dich X gom hai mudi vd chat rdn Y gom hai kim loai Hai muoi X vd hai kim loai Y Idn lilat Id: D Cu(N03)2; AgNOg va Cu; Ag C Fe(N03)2; Fe(N03)3 va Cu; Ag B Cu(N03)2; Fe(N03)2 va Ag; Cu A Cu(N03)2; Fe(N03)2 va Cu; Fe (Dai hoc 2013 khoi A) Khong mat nhieu thcfi gian de nhan dap an can t i m la B That vay, ta loai trii A, v i Fe t r o n g Y phai tac dung vdi Cu(N03)2 t r o n g X nen sau phan ufng khong the thu difac nhOfng chat nhtf the; tiicrng tii la loai triT C vi Cu t r o n g Y phai tac dung vdi Fe(N03)3 t r o n g X, va cuoi cung loai trCr D vi Cu t r o n g Y phai tac dung vdi AgN03 t r o n g X Ro r a n g phifcfng phap loai triT hgp da to r o tfu the t r o n g giai trac nghiem! t r o n g trLfcfng Can biet them rang phifcfng phap loai tnlf khong phai chi dimg cho cac cau trac nghiem ly thuyet Trong mot so' bai toan ma hudng di mu mcJ, chiia the dinh h i n h t h i phucfng phap loai trif cung g i u p ta loai bo cac phifong an sai, ti^ xac dinh diicfc dap an ciia bai toan Cac em hay quan sat v i du sau: Hoa tan hodn todn m gam Al bdng dung dich HNO3 lodng, thu dugc 5,376 lit (dktc) hSn hgp X gom N2, N2O vd dung dich chiia 8m gam mudi Tl khoi cua X so vdi H2 bdng 18 Gia tri cua m Id A 17,28 B 19,44 C 18,90 D 21,60 (Dai hpc 2013 - khoi A) r Rat nhieu hoc sink nhanh chong xdc dinh dugc buac ddu tien d ddy la phdi tim so mol tilng Do Id huang di diing! Theo dU kien dd cho, ta cd so mol N2 = so mol NoO = 0,12 mol Tuy nhien huang di tiep ddi vdi mot so em cd the Id chua ro rang, dd ta dung philang phdp loai triC: Be y rdng tong so mol electron md N*^ dd nhan de too N2 vd NoO = 0,12.10 + 0,12.8 = 2,16 mol, do: 17 28 - Loai tril A, vi neu chon m = 17,28 thi nAi -—'— = 0,64 mol Khi dd 27 rieiectron Ai cho = 0,64.3 = 1,92 mol < 2,16 mol 18 90 — • Loai trii C, vi neu chon m = 18,90 thi nAi =—'—0,70 mol Khi dd 27 neiectron Ai cho = 0,70.3 = 2,10 mol < 2,16 mol 19 44 - Loai trie B, vi neu chon m = 19,44 thi UAI =— = 0,72 mol.Khi dd 2.1 n-eiectron doAi cho = 0,72.3 = 2,16 chitng to khdng tgo NH4NO3 Do dd rn.,nu6i = rn + 62(10.0,12 + 8.0,12) ^ 8m m - 19,13-^19,44 Vdy chon D Cdch khdc Nhif tren da noi, ta chi dung phuang phap loai triT k h i hiTdrng giai bai toan mcf ho, chifa xac dinh Neu da n&m dtfcfc phiicfng phap giai toan ve k i m loai tac dung vori H N O a , bai n a y di/gc giai theo bao toan electron nhuf sau: Ta cd so mol N2 = sd mol N2O = 0,12 mol Gid sit mud'i ihu diigc gom ~ mol AKNOsJs vd x mol NH4NO3 27 + x - m x = 720 T a c d 213 — Bao todn electron cho — = 0,12.10 + 0,12.8 + - ^ « 11 720 m = 21,6 Hoac v i du sau t h i phi/ang phap loai trCf the h i e n ro lAi diem giai trac nghiem: Hidro hda hodn todn 0,025 mol hdn hgp X gom hai andehit can 1,12 lit H2 (dkc) Mat khdc, cho cung lUgng X tren phdn ling vdi mot lUgng dU dung dich AgNOs NH3 thi thu dugc 8,64 gam Ag Cong thiCc can tgo cda hai andehit X Id: A OHC-CH2-CHO B H-CHO vd vd OHC- OHC-CH2-CHO CH2-CH2CHO C C H s C - C H O vd D CH2=CH-CH0 vd OHCCH2-CHO OHC-CHO Gidi Ta CO so lien ket n truns "H 0,05 binh = — ^ = — = nen loai trie B, C "KK 0,025 hh ' Mat khdc so mol Ag = 0,08 tiic ux •' nAg = : 3,2 nen phdi loai tril A Yqy chon D D i e u dac b i e t l a d nhCfng cau l y t h u y e t h a y b a i t o a n m a dcr l i e u da cho l a k h o n g d a y d u t h i phifcfng p h a p l o a i t n f t o r o l a m o t sir l i i a chon t o i UU T h a t vay, t a x e t v i d u sau: X la chat hOu ca tdc dung vai Na diC cho so mol H2 bay b&ng so mol NaOH can diing de trung hba het cUng luang X tren Cong thiCc phan tit cila X Id A C4H8O2 C C7H12O2 B CeHi403 D CgHioOz De d a n g loai trtr B v i CGHMOS k h o n g p h a n tfng di/oc vcri N a O H Cung loai tvii A, C v i C4H8O2 v a C7H12O2 g i a i phong so m o l H2 = — so m o l N a O H Vdy chon D Hoac a v i d u sau, c6 v6 so' h n h o p ancol t h o a m a n de b a i n e n n e u sa da vao g i a thie't se k h o n g t h e c6 k e t qua: Cho hon hap X gom hai ancol Dot chdy hodn todn 0,3 mol hSn hap X thu dugc 22 gam CO2 Mat khdc 0,3 mol X tdc dung vai Na dU diiac 5,6 lit H2 (dkc) Hai ancol dd cho Id: A CH3OH vd C2H5OH C C2H/OH)2 B CH3OH vd C3HdOH)2 D CH3OH vd C3H6(OH)2 vd C3H5(OH)3 T a l o a i t r i f n g a y A , B v a C h n h o p c6 so C t r u n g b i n h = so' n h o m O H = 1,66 V a y c h o n D , tufc ancol t r e n l a C H O H v a C3H5(OH)3 trung binh - ^ B A I TAP AP D U N G Cho b o t M g va Fe vao d u n g d i c h g o m A g N v a Cu(N03)2 Sau k h i cac p h a n ufng x a y r a h o a n t o a n , t h u difcfc d u n g dich X g o m b a m u o i v a c h a t r a n Y g o m h a i k i m l o a i B a m u o i t r o n g X v a h a i k i m l o a i t r o n g Y I a n li/cft l a : A M g ( N ) ; Fe(N03)2; F e ( N ) v a Fe; Cu B Cu(N03)2; A g N O s ; F e ( N ) v a A g ; Cu C M g ( N ) ; F e ( N ) ; Cu(N03)2 v a A g ; Cu D Mg(N03)2; Fe(N03)2; Cu(N03)2 v a A g ; Cu Gidi Ro rang dap an can tim Id D That vdy, ta loai trit A, vi Fe vd Cu Y phdi tdc dung vai FefNOsJs X nen sau phdn ring khong the thu dugc nhQng chat nhii the; tuang tu Id loai trie B vi Cu Y phdi tdc dung vai FefNOsJs vd AgNOs X, vd cuoi cung loai trit C vi Cu Y phdi tdc dung vai Fe(N0s)3 X Vdy chon D C h o h o n hcfp g o m F e v a M g v a o d u n g d i c h A g N O a , k h i c a c p h a n uTng x a y r a h o a n t o a n t h u diicfc d u n g d i c h X ( g o m h a i muo'i) v a c h a t rfin Y ( g o m h a i k i m loai) H a i muoi t r o n g X l a : A Mg(N03)2 v a Fe(N03)2 B Fe(N03)2 v a AgNOa C Fe(N03)3 v a Mg(N03)2 ' D AgNOg v a Mg(N03)^_ Gidi Chu y rdng rdn Y d day Id Ag vd Fe (dang bdi tap cho hdn hap kim loai vdo dung dich gom hdn hap cdc muoi thi rdn thu dugc phdi Uu tien Id cdc kim loai CO tinh khit yeu nhdt) Do di ddng loai trii cdc phitang dn B, C, D vd lua chon dap dn A Vdy chon A T h i n g h i e m n a o s a u d a y chufng to t r o n g p h a n tuf glucozcf c6 n h o m h i d r o x y l ? A Khijf h o a n t o a n glucozcf t h a n h h e x a n B C h o glucozcf t a c d u n g vdri C u ( O H ) C T i e n h a n h p h a n ufng t a o e s t e c i i a g l u c o z a vdri a n h i d r i t a x e t i c D T h i f c h i e n p h a n ufng t r a n g b a c Gidi Loai trie A vi day Id thi nghiem de chiing minh phdn td glucoza c6 6C khong phdn nhdnh Loai trii B vi ddy la thi nghiem de chiing minh phdn tit glucoza c6 cdc nhom OH ditng ke Loai triiD vi ddy la thi nghiem de chitng minh phdn tic glucoza c6 nhom -CHO Vdy chon C C h o p h a n ijfng : N ( k ) + H ( k ) < > 2NH3 ( k ) ; AH = -92 k J H a i bien phap deu l a m c a n b a n g c h u y e n d i c h theo c h i e u t h u a n l a A g i a m n h i e t v a g i a m a p s u a t B t a n g n h i e t v a t a n g a p s u a t C g i a m n h i e t v a t a n g ^p s u a t D t a n g n h i e t v a g i a m a p s u a t Gidi Loai trii A vi gidm dp suat thi can bdng se chuyen dich theo chieu Loai trie B, D vi tang nhiet dp thi can bdng se chuyen dich theo chieu nghich nghich Vdy chon C Cho phircfng t r i n h hoa hoc: 2X + 2NaOH > 2CH4 + K2CO3 + NagCOg Chat X la A CH2(COOK)2 B CH2(COONa)2 C C H C O O K D CHgCOONa Gidi Loai trii A, B vi khong bdo tocin H a ve Loai trii D vi Xphdi chiia nguyen to K Vdy chon C Cac polime thuoc loai tcf nhan tao la A tot visco; ta nilon-6,6; tcf capron B tcf t a m ; tcf vinilon; tcf visco C ta nilon-6,6; ta capron; len D ta visco; ta xenluloza axetat; ta dong-arnoniac (Dai hoc 2012 - khoi B) Gidi Chii y rdng vai dang bdi tap nay, chi can phdt hicn mot loai ta niSi ddy da cho khong phdi Id to nhdn tao thi ta loai trii Vdy di ddng loai trii A, B, C vd chon D (ta nilon-6,6; tdni; len Id ta thien ta capron; ta vinilon Id ta tong hap, ta nhien) Vdy chon C Trong cac polime: ta thm, scfi bong, ta visco, ta nilon-6, ta nitron, nhOTng polime CO nguon go'c t\i xenluloza la D sgi bong va ta visco C sgi bong, ta visco va ta nilon-6 B ta visco va ta nilon-6 A ta t k m , sgi bong va ta n i t r o n (Dai hoc 2013 - khoi B) Gidi Tuang nitron; tu nhu can a tren, ta loai trii A, B, C vd chon D (ta tdm; ta ta nilon-6 khong c6 nguon goc til xenluloza) Vdy chon D Cho cac phat hiiu sau: (a) Trong bang tuan hoan cac nguyen to hoa hoc, crom thuoc chu k i 4, nhom VIB (b) Cac oxit cua crom deu la oxit baza (c) Trong cac hgp chat, so oxi hoa cao nhat cua crom la -H6 (d) Trong cac phan tfng hoa hoc, hgp chat crom(III) chi dong vai tro chat oxi hoa (e) K h i phan ufng vdi k h i CI2 dii, crom tao hgp chat crom(III) Trong cac phat bieu tren, nhijfng phat bieu dung la: A (a), (b) va (e) B (a), (c) va (e) C (b), (d) va (e) D (b), (c) va (e) (Dai hoc 2013 - khoi A) to Gidi De y rdng b) Id phdt bieu sai nen loai trie A, C, D (CrO Id oxit baza; CrOs la oxit axit; CrsOs Id oxit liiang tinh) Vay chon B Cho cac chat : caprolactam (1), isopropylbenzen (2), acrilonitrin (3), glyxin (4), v i n y l axetat (5) Cac chat c6 kha nang t h a m gia phan uTng trung hcfp tao polime la A (1), (2) va (3) B (1) (2) va (5) C (1), (3) va (5) D (3), (4) va (5) Gidi Vi caprolactam (1) cho dugc phan iXng triing hgp, nhitng isopropylbenzen (2) khong cho dugc phan iCng triing hgp nen loai trit D, A, B Vay chon C 10 Cho can bang hoa hoc sau: 2SO2 (k) + O2 (k) < > 2SO3 (k) ; AH < Cho cac bien phap : (1) tang nhiet do, (2) tang ap suat chung cua he phan ufng, (3) nhiet do, (4) diing them chat xuc tac V2O5, (5) giam nong SO3, (6) giam ap suat chung cua he phan ufng NhOfng bien phap nao lam can bang tren chuyen dich theo chieu thuan? A (2), (3), (4), (6) B (1), (2), (4) C (1), (2), (4), (5) D (2), (3), (5) Gidi Chu y rdng chat xuc tdc (4) khong Idm can bdng chuyen dich nen loai trie A, B, C Vgy chon D 11 Cho bon dung dich c6 cung nong mol sau day: (1) H N C H C O O H , (2) C H C O O H , (3) CH3CH2NH2 va (4) C2H3COOH Day xep theo thuf tiT p H tang dan la: A (3), (1), (2), (4) B (4), (1), (2), (3) C (2), (3), (1), (4) - D (4), (2), (1), (3) Gidi Khong it hoc sinh boi roi a cdu hoi ndy khong ndm dUgc luc axit cua axit chita no C2H3COOH Id mgnh hay yeu han so vai axit CH3COOH phiiang phap loai trie nhu Hay dung sau: Vi dung dich CH3CH2NH2 c6 moi truang baza nen pH cua dung dich ndy phdi Ian nhdt so dung dich Vgy loai trii A, C NhiCng dung dich NHoCH^COOH c6 pH xdp xi Id 7, dung dich CH3COOH phdi CO pH < nen loai trie tiep B Vgy chon D 12 Cho hSn hcfp X gom Fe203, ZnO va Cu tac dung \6i dung dich H C l (diT) thu di/cfc dung dich Y va phan khong tan Z Cho Y tac dung vc;i dung dich NaOH (loang, du) thu d'Jgc ket ttia: A Fe(0H)3 va Zn(0H)2 B Fe(0H)2 Cu(0H)2 v^ Zn(0H)2 C Fe(0H)3 D Fe(0H)2 Cu(0H)2 11 - Loai tritA (c6 so n trung binh Id 1) - Loai trie B (c6 3Fe^" + NO + 2H2O 0,05mol Fe'" + Ag" Fe^" 0,0125 m o l Vay + Ag 0,0125 m o l m k e t t L i a = m A g c i + niAg = 0,2.143,5 + 0,0125.108 = 30,05 g a m + C a c h d u n g d i n h l u a t bao t o a n e l e c t r o n CHO NHAN Fe Fe +3 + 0,05mol Cu 3e NO: + 4H" + 0,15mol — 3e -> N O 0,05mol > Cu"^ + 2e 0,025mol Vay Ag" + 0,05mol + 2H20(*) 0,0375mol e > 0,0125mol Ag 0,0125mol = 0,2.143,5 + 0,0125.108 - 30,05 gam Vay chpn B mkettik = niAgci + m A g •Lu:u V + C a n cuf vao v i t r i cac cap o x i hoa khuf t r o n g day d i e n hoa, thuf t i i cac p h a n ufng oxi hoa khuf x a y r a k h i cho X vao d u n g d i c h AgNOa dii k h i g i a i theo each t h o n g thtfctog p h a i l a : 3Fe'" + H " + Fe > NO: 2+ -> Fe 3+ + 3Fe^" + NO + 2H2O Ag + each g i a i t h e o bao t o a n e l e c t r o n , chii y r k n g N O , t h i nghiem da d u n g dtf n e n t o a n bo H " t r o n g t h i n g h i e m da p h a n ufng h e t t h e o (*) + Co t h e n h a n r a (*) tii p h t f o n g t r i n h i o n x a y r a t r o n g b a i : Fe + 4H" + NO, > Fe^" 3Fe^" + H " + N O : + N O + 2H2O > 3Fe^" + N O + H O 28 V i d u 6: H o n h o p X chufa b a a x i t cacboxylic deu d o n chufc, m a c h h d , g o m mot axit no v a h a i a x i t k h o n g no deu c6 m o t l i e n ke't d o i ( C = C ) Cho m g a m X tac d u n g viTa du vdi 150 m l d u n g d i c h N a O H M , t h u dtfcfc 25,56 g a m hon hap muo'i D o t chay h o a n t o a n m g a m X , h a p t h u t o a n bo s a n p h a m chay bang d u n g d i c h N a O H dii, kho'i Itfcfng d u n g d i c h t a n g t h e m 40,08 g a m T o n g khoi lifcfng cua h a i a x i t cacboxylic k h o n g no t r o n g m g a m X l a A 15,36 g a m B 9,96 g a m C 18,96 g a m D 12,06 (Dai • Nhdn gam hoc 2013-kh6i A) xet K h o n g v a n d u n g di/gc d i n h l u a t bao t o a n nao de r i i t n g d n h o n I d i g i a i b a i toan, ngoai viec d u n g bao t o a n n g u y e n to' C v a H de suy r a so m o l C O v a H O thu difoc dot X t h a y v i v i e t cac p h a n ufng chay • Giai Goi cong thufc a x i t no l a C n H n ; cong thufc t r u n g b i n h a x i t chifa no l a CmH2m - O Goi a l a so' m o l a x i t no; b l a so' m o l a x i t chifa no a = 0,15 a + b = 0,3 Ta CO he; a(l n + ) + b ( m + ) = , 44(na + b m ) +18(an + b m - b) = 40,08 -t=> b = 0,15 an + b m = , Rut r a n + m = 4,6 C h i j y r a n g t a p h a i c6 m > n e n c h i c6 n = ; m = 3,6 l a p h u hcfp Vay m2 axit khong no = b ( m + 30) = 0,15(14.3,6 + 30) = 12,06 (gam) V a y chon D • Luu y K h o n g p h a i b a t cuf b a i t o a n H o a nao c u n g v a n d u n g d i n h l u a t bao t o a n k h i giai T h o n g thircfng, cac d a n g t o a n ve tdc p h a n urng h o a hoc; t o a n ve h a n g so can b a n g K o ; t o a n ve h i d r o x i t \\idng t i n h ; t o a n ve xac d i n h p H cua d u n g d i c h ; toan ve cac l o a i h a t co b a n (p; n ; e) h a u n h i i k h o n g sijf d u n g d e n c a c d i n h luat bao t o a n V i d u 7: Cho m g a m h n hcfp X g o m a x i t a x e t i c , a x i t fomic v a a x i t oxalic tac d u n g vdi N a H C O g (dH) t h i t h u dUgrc 15,68 l i t k h i C O ( d k t c ) M a t k h a c , dot chay h o a n t o a n c u n g lifcfng X t r e n can 8,96 l i t k h i O2 ( d k t c ) , t h u dtfoc H O v a 35,2 g a m C O G i a t r i cua m l a A 33,2 • Nhdn B 40,8 C 31,2 D 29,6 xet D a so' hoc s i n h n h a n r a n g a y b a i t o a n difoc g i a i t h e o d i n h l u a t bao t o a n kho'i li/Ong, n h i / n g v a n de l a chifa c6 so' g a m H O s i n h r a k h i dot c h a y X 29 De y rang CO2 sinh id hon hop X tac dung vdri NaHCOs tuan theo quy luat: axit dan chufc giai phong CO2 theo t i le mol : ; axit n h i chufc giai phong CO2 theo t i le mol : 2, tufc axit c6 phan tuf va axit c6 phan tijr Ian iLfgt giai phong CO2 theo cac t i le tiicfng uTng : va : nen bai toan cung lien he den d i n h luat bao toan nguyen to O • QMi -( Dung d i n h luat bao toan kho'i lifong kem dinh luat bao toan nguyen to' Goi a, b, c la so mol C H C O O H , HCOOH va C2H2O4, ta c6: a + b + 2c - Bao toan oxi cho: 2a + 2b + 4c + 2.0,4 = 2.0,8 + n„ o 8,96 22,4 = 35,2 + 10,8 O 0,7 0,6 (mol) o m ^ ^ „ = 10,8 Vay bao toan kho'i li/cfng cho m + 32 gam m - 33,2 Vay chon A Bai toan cung c6 the giai theo each thong thiic;ng la goi so" mol Ian lu'cft cac axit la a, b, c roi viet cac phiiong t r i n h phan ufng xay CJ day can chii y de'n phan Lfng chay v i c6 lien quan den so mol O2 : CH3COOH + 2O2 — 2H2O + 2H2O 2CO2 + 4CO2 2H00C-C00ri + O2 2CO2 2HC00H + O2 ^ , 15,68 a + b + 2c = - ^ — 22,4 K h i ta c6 he: za- b + 2H2O ^ =0,7 a-0,1 c _ 8,96 -=0,4 2 " b = 0,2 22,4 c = 0,2 35 2a + b + 2c = ^ = 0,8 44 Vay m = 60a + 46b + 90c = 33,2 (gam) Tuy nhien each giai to be' tSc k h i them vao h6n hcfp X mot so axit cacboxylic khae nhir C2H5COOH ; CH2=CH-C00H ; HOOC-CH=CH-COOH , vi he phtfcfng t r i n h luc khong the giai dLfcre gia t r i cac nghiem so Trong k h i do, vdri each giai dung dinh luat bao toan khoi liigfng ket hgp vori dinh luat bao toan nguyen to or tren, ta bie't rang du hon hop c6 them vao bao nhieu axit cacboxylic di chang niJa t h i gia t r i m van kion co dinh la 33,2 Day cung la nhtfgc diem cua each giai cac bai toan Hoa theo phifcfng phap thong thtfcfng ma khong thong qua dinh luat 30 Chinh V ] vay viec biet ke't hop dinh luat se cho ket qua nhanh chong hon so voi chi dung mot dinh luat Day la dieu ma cac hoc sinh can nam k h i giai cac bai toan Hoa hoc phtiTc tap, chua ke qua cac em se phat t r i o n kha nang t u hoc Hoa len nhieu Ian Thong thtfcmg k h i ket hop d i n h luat, t h i dinh luat bao toan khoi liTong difoc dung song song vdi dinh luat bao toan nguyen to' se cho ket qua tot nha't Cung CO triJcfng hop dinh luat bao toan electron du'Oc dimg kem vori d i n h luat bao toan nguyen to Ta se xet them mot so v i du cho viec ket hop d i n h luat qua cac bai toan diTdi day: Vi d u 8: Nung 4,2 gam h6n hop X gom Fe, A l , Zn, Mg va Cu oxi mot thcfi gian difoc 4,68 gam hon hop rSn Y Hoa tan hoan toan Y H S O dac, nong dii difoc 0,896 lit (dice) S O la san pham khijf nhat So mol H2SO4 da phan u"ng la A 0,18 B 0,14 C 0,16 D 0,11 • Nhdn xet + Goi a la so mol H S O can t i m , nhd bao toan nguyen to S se t i n h di/gc so mol S (tijfc so mol ion SO^, ) c6 muoi, sau dung bao toan kho'i Itfong se tim doge a Cu the l a bao toan S cho n,, = n S/muoi , = n „ „ , , - n _ , , = (a - 0,04) S O : /mu(')i M.SOj SO, ^ mol ' + Cung C O the giai theo bao toan electron bai toan c6 xay cac qua t r i n h oxi hoa khijf Tuy nhien can lOu y rang khong goi a, b, c, d , e la so mol k i m loai ban dau, Chi can dai dien kim loai da cho la k i m loai M (voi so' mol la a; hoa t r i x) de giam hdt an so' o Giai + Dung dinh luat bao toan khoi loong kem dinh luat bao toan nguyen to Ta C O 4,68 + 98a = 4,2 + 96(a - 0,04) + 64.0,04 + 18a a = 0,11 mol Vay chpn D + Dung dinh luat bao toan electron kem dinh luat bao toan nguyen to' De y rang k i m loai M cuoi bai da h i oxi hoa toan bo t h a n h M"""; O2 cuoi bai bi khCf va S^*^ cudi bai bi khuf Theo de so mol O2 da phan ufng - ^ 0,015 (m.ol) Cac qua t r i n h cho, nhan electron: Clio M a mol > NHAN + xe xa mol + O2 0,015mol S'^ + 4e > T+2 0,06mol 2e 0,04mol > S'* 0,08mol Vay xa = 0,06 + 0,08 = 0,14 31 [...]... todn oxi de loai trie nhit sau: 0,4.2 + 0 , 2 5 - 0 , 2 2 - Loai trie A vi x = 0,2 thi so O trung = 4,33 (vd li) binh 0,15 vi x = 0,375 thi so O trung binh = ^'^"^ ^ 0 , 2 5 — 0 , 3 7 5 2 _ ^ 0,15 - Loai trilB 0 4" "2/ ( Q 25 0 - Loai trie C vi x = 0,225 thi so O trung binh = ——'—' Vdy chon Liiu 2 ~ ~ ^ D y - Cong thiic tinh so O trung binh = hon hiip - Vi A chiea 20; B chiea 40 trong 2 < so O trung... het, mdi tdi lugt Fe phdn ilng Vdy: Loqi tril A, do Mg con thi Fe chila phdn ling nen khong trong dung dich Y, ddn den T khong the cd Fe203 the cd muoi sdt Loqi trii B,-do Mg ud Fe phdn iCng het thi long khoi liiang magie oxit va sdt oxit tqo thdnh trong T phdi Ian hon tdng khdi liicmg Mg va Fe ban ddu, tOc m' > m Loqi trii C, do Fe con trong Z thi CuCl2phdi het, ddn den T khong the cd CuO Vdy chgn D... l x = 0,08 4x + 2 y - 0 , 3 6 [y = 0,02 - Loai trii A , vi neu X chiem 83,33% khoi lugng hdn hap thi ta phdi c6: -0,08.30 = = 24 (vd It) ^ 0,02 - Loqi Irii C, vi neu X chiem 75% khoi luang hon hap thi ta phdi c6: 0,08.30,10D_^„^3g = " = 40 (vd It) 0,02 - Loqi trie D, vi neu X chiem 90% khoi lugng hon hap thi ta phdi c6: 0 , 0 O 0 1 0 0 _ Q ^ ^ 3 3^ = ^ = 1X23 M ^ (volt) 0,02 Vdy chgn B hiiu y - Khong... phdi loai trit C, vi neu trung binh Id 2) Nhung di so C trung Vay chon binh Y Id C3H6 thi X budc phdi Id 2, khi do phdi Id HCHO c6 n ^ ^ = n^,,^^^, (trdi gid (do so C thiet) D 31 H 6 n h g p M g o m a n k a n A v a a n k e n B D o t chay h o ^ n t o a n 7,84 Ut (dkc) hcri M dtfgc 55 g a m CO2 v a 27 g a m H2O C o n g thijfc p h a n tuf A , B I a n lifgt l a C 4 H 1 0 va C C H 4 va A B C3H6 D C4H8 C 2... Cu A Zn, Fe, Cu Gidi Chu y rdng thii tii phdn ling cua cac kim loqi vdi dung dich CuCl2 Id Mg >Al>Zn> Fe 12 Vdy: Loqi trie B, vi dung Loai Id dich Z khi do chi chiia Id hon hap W nhu de yeu khong phai trie A, vi dung dich MgCl2, ddn den W chi Id MgO, cdu MgClo vd Z khi do chiia AICI3, ddn den W ciing chi MgO Load trilD, vi Y khong Vdy chgn the gom Zn; Cu (do Y con Zn thi ciing buoc phai con Fe) C 1... rdng ancol HOCH=CHOH khong ben dd chuyen thdnh andehit glycolic HOCH2CHO Do dd este E phdi cd dang RCOOCH=CHOOCR, tiic E phdi cd so C chdn (loai trit A, B) Mat khdc vai cong thicc RCOOCH=CHOOCR phdn ti} (loqi trit D) Vqy chon C thi E phdi cd it nhdt 3 n trong 22 Dot chay hoan toan mot liicfng ancol X tao ra 0,4 mol CO2 0,5 mol H2O X tac dung vdri Cu(0H)2 tao ra dung dich mau xanh lam Oxi hoa X bang... i a i quyet r a t n h a n h gon T h a t vay xet thcfi d i e m ban dau v a liic k e t thiic t h i n g h i e m , t a t h a y c h i c6 Fe v a Cu da cho e l e c t r o n de t r d t h a n h Fe'^ v a Cu^'^; tifcfng t\i l a N^^ t r o n g N O ^ v a Ag"" da n h a n electron de t h a n h N"^^ v a A g • Gidi + Cach t h o n g thifcfng F c : 0,05 m o l C u : 0,025 m o l Theo de t a c6 • H - : 0 2 5 m o l NO^ :... 1,66 = so nhom OH , nen: - Loai trie A (c6 so nhom OH trung binh Id 1) - Loai trie B (c6 so nhom OH trung binh khac - Loai trii: C (c6 2 < so C trung Vdy chgn 1 binh so C trung binh) < 3) D 15 m 2 1 Thiiy phan este mach hd E (chi chufa chufc este) trong moi trufcfng axit thu diigc hon hap san pham chi gom mot axit cacboxyUc va andehit glycoHc H O C H 2 C H O Cong thufc phan tuf cua E la A C7H10O4... cho ta he: 8 l a + 9 9 b + 125c = 24 a + b + c = 0,4 Gidi ra b < 0 (loai) Gidi rah (loai) c = 0,05 - Loai trii D vi M Id Ca cho ta he: 56a + 7 4 b + 100c = 24 a + b + c = 0,4 < 0 c = 0,05 Vdy chgn Liiu nhanh A y: Co the nhu khong can dung da kien so gam hdn hap la 24 gam ud gidi sau: M C O H ) ^ vd M C O , , ta c6 Ggi a, b, c Idn lugt Id so mol MO, a + b + c = 1,12 22,4 100.39,2 100.98 ^ = 0,4 Af = 24... hien tinh thdy "sau mot thai gian mot trong chon thai gian luang khi hud'ng cho luang hSn hgp A tdc dung vai ke't tua thu duac dd vuat qud x gam" thu duac hon hgp A deu cho dugc phdn dd vUat qua y lit", thi tat cd cdc ling vai chat B Van dung ngay ddp dn can tim Id A md khong can thong dieu ndy c6 qua tinh toan nhu chat hay chat the tren 33 X l a h o n hcfp g o m 2 ancol no, m a c h h d D o t chay h