www.vietmaths.comSee on vietmaths.com- 1 -CNG HO X HI CH NGHA VIT NAM c lp - T do - Hnh phc ----------------------------------------------------- TI SNG KIN KINH NGHIM S YU L LCH -H v tn: L c Tng -Ngy, thng, nm, sinh: 01 04 1986-Nm vo ngnh: 01 04 2009 -Chc v: Gio vin -n v cng tc: Trng THPT Chng M B -H o to: Chnh qui -Trnh chuyn mn: C nhn s phm Ho Hc -B mn ging dy: Ho Hc -Ngoi ng:Ting Anh www.vietmaths.comSee on vietmaths.com- 2 --PHN I TNG QUAN I. L do chn ti: -HohclmnkhoahccbntrongcctrngTHCSvTHPT.yl mn cc em mi c trang b kin thc t khi hc lp 8 bc THCS. Tuy nhin, y cngl mnthngxuyns dngthitt nghipTHPTvlmttrong ba mn bt buc trong k thi tuyn sinh vo H, C, THCN khi A, B. - K t nm 2007, B Gio Dc v o To chuyn cu trc thi tuyn sinh ihc,caongmnhottlunsangtrcnghim100%.iucngng ngha trong vng 90 pht, hc sinh phi tht bnh tnh la chn phng n tr li ti u nht trong thi gian ngn nht.Nm bt c iu , cc ging vin i hc, cao ng, cc chuyn gia v cc nh gio c nhiu kinh nghim xut bn rt nhiu sch vtiliuthamkhovccphngphpgiinhanhtrcnghim.Mtviphng phpphiknl:botonkhilng,botonelectron,botonintch, phngphpngcho,trungbnh,thvmtphngphpkhhuhiul phng php qui i. - Vi xu th trc nghim khch quan hin nay th nhanh v chnh xc l hai yu t rt quan trng trong khi lm bi kim tra cng nh trong cc k thi. V vy, vn dng ccc phng phpgii nhanhcha mk nng bm mytnhcnggp phn vo vic gii nhanh bi tp trc nghim. Trong vic bm my tnh cng th hin c phng php gii v kh nng t duytru tng ca hc sinh khi lm bi. Nuc dp quansthcsinhkhilm bichngtakhngkhi ngcnhinc nhng hc sinh bm my tnh nhanh nh chp v c hc sinh bm my chm nh ra.-Hnthna,thngquaccthiihc,caonghinnaytinhnthy trong thi c nhiu bi tp lin quan n axit nitric. V gii nhanh nhng bi tp chng ta thng p dng phng php bo ton electron v phng php qui i.-Qua3nmgingdytrngTHPTkthpvinhngkinthctchlu c khi ngi trn ging ng i hc ti mnh dn a ra tng Rn luyn k nng bm my tnh gii nhanh bi ton trc nghim v axitnitric. II. Mc ch nghin cu - Nghin cu nhng dng bi ton v axit nitric thng gp trong cc thiwww.vietmaths.comSee on vietmaths.com- 3 -tuyn sinh i hc, cao ng. - xut nhng tng gii nhanh bi ton axit nitric trn my tnh,gp phn nng cao cht lng ging dy b mn trng ph thng v l hanh trang vng chc cc em chun b bc vo k thi TSH. - Bn thn c c hi nghin cu, tm hiu v vn dng cc tng vo cng tc ging dy ca bn thn sau ny. III. Nhim v nghin cu - Nghin cu ni dung axit nitric lp 11. ng thi tm ra nhng dng bi tp in hnh thng gp trong cc thi TSH. - Nghin cu phng php bo ton electron, phng php qui i v vn dng phng php gii bi tp trc nghim. - Tm ra hng gii quyt nhanh cc bi ton da vo k nng bm my tnh. IV. i tng nghin cu - Tin hnh nghin cu trn i tng hc sinh trng THPT Chng M B H Ni kt lun nhng tng, gi thuyt m ti a ra cn b sung g khng. V. Phng php nghin cu + Bc 1: Trn c s nm vng ni dung trng tm bi axit nitric lp 11 v nghin cu k nhng cu hi thi TSH lin quan n bi tp axit nitric, tc gi la chn, su tm nhng bi tp trc nghim c gii nhanh bng phng php bo ton electron v phng php qui i. + Bc 2: a ra nhng tng gii nhanh nhng bi tp chn bc 1 trn my tnh (Casio fx 500MS, ..). + Bc 3: Tin hnh thc nghim s phm trn i tng hc sinh. + Bc 4: Thu thp v x l s liu, rt ra kt lun. VI. Phm vi v thi gian nghin cu ca ti. - Do iu kin thi gian v hn ch ca mt sng kin kinh nghim nn ti chcthnghincutrnphmvihp(thcnghim1trngTHPTnitcgi cng tc) v ch nghn cu nhng bi tp nh c kh nng gii nhanh trn my tnh. - Phm vi p dng: + Kim loi, hn hp kim loi tc dng vi HNO3 hoc hn hp HNO3 v H2SO4 c + Bi ton kim loi, oxit tc dng vi axit HNO3. + Bi ton kim loi, hp cht vi lu hunh tc dng vi HNO3 www.vietmaths.comSee on vietmaths.com- 4 -PHN II: NI DUNG SNG KIN KINH NGHIM I. Tnh hnh thc t trc khi thc hin ti. -Quanhngnmgingdytitrngphthngvnhiunmigiaskhi ngi trn gh ging ng i hc, ti nhn thy rt nhiu hc sinh c loay hoay vit rt nhiu phng trnh phn ng khi cho hn hp kim loi hoc oxit kim loi tc dng vi axit HNO3. iu , s mt nhiu thi gian lm bi v i khi khng lm ra c kt qu.- V vy, s dng phng php qui i v bo ton electron l nhng cng c ti u gii nhng quyt nhng bi ton dng ny. - Mti tng hc sinh khc chng ta cng hay gp l qu lm dng my tnh (ci g cng bm v bm qu chi li), do s rt tn thi gian lm bi. -Vvy,tnglrtquantrng,giphcsinh nhhngccchgiinhanhbitontrnmytnhthayvccemphivitrtnhiutrnnhp,iuny hon ton khng hp l trong bi thi trc nghim. - T thc t trn, tc gi xin trnh by nhng gii php, tng gii nhanh nhng bi ton axit nitric trn my tnh. II. Bin php thc hin ti. II.1. Nhng kin thc cn trang b.-Xc nh c y cc cht kh, cht oxi ho. -Vit c cc qu trnh kh v qu trnh oxi ho. -p dng nh lut bo ton electron.-X l cc d kin bi ton: s mol, th tch kh, khi lng.. Cc kin thc v phn ng oxi ho kh hc sinh c trang b lp 10. Trong khun kh ti, ti ch xin cp ti cc bc gii nhanh bi ton axit nitric trn my tnh trong thi TSH. II.2. Nhng im cn lu . II.2.1. Phng php bo ton electron. -Ch p dng cho bi ton xy ra cc phn ng oxi ho kh. -Xc nh v vit y cc qu trnh kh, qu trnh oxi ho. -nh lut bo ton electron: e nhng = e nhn. www.vietmaths.comSee on vietmaths.com- 5 -II.2.2. Php php qui i - Phm vi p dng:+ Kim loi, oxit kim loi tc dng vi dung dch HNO3. + Kim loi v hp cht kim loi vi lu hunh tc dng vi HNO3 - Hng qui i: Mt bi ton c th c nhiu hng qui i khc nhau: + Qui i hn hp nhiu cht v hai hay ch mt cht. V d: Hn hp: Fe, FeO, Fe2O3, Fe3O4

+ Qui i hn hp nhiu cht v cc nguyn t tng ng: V d: Hn hp: Fe, FeS, FeS2, Cu, CuS, CuS2, Cu2S, S Fu, Cu, S + Bng kinh nghim ca mnh, tc gi nhn thy hng qui i v cc nguyn t tng ng l n gin v d hiu hn c. V vy, trong cc v d di y tc gi ch trnh by hng qui i ny. - Khi p dng phng php qui i, cn phi tun th 3 nguyn tc: + Bo ton nguyn t + Bo ton s oxi ho + S electron nhng, nhn l khng thay i. II.3. Mt s cng thc p dng cn nh: II.3.1.Tnh khi lng mui - Phm vi p dng: + kim loi tc dng vi HNO3 hoc H2SO4 c+ Vi HNO3: nNO3 to mui = ne nhn = 2 2 2 4 33. 8 10 8NO NO NO N NHNOn n n n n + + + +. Fe, FeO Fe, Fe2O3 Fe2O3, FeO FeO mmui = mkim loi + 2 2 2 4 362 (3. 8 10 ) 80NO NO NO N NHNOn n n n n + + + + mmui = mkim loi + mgc axit (1.1) (1.2) www.vietmaths.comSee on vietmaths.com- 6 -+ Vi hn hp H2SO4 c v HNO3: (thng khng to mui amoni)

Tuy nhin, trong cc bi tp ta cng thng gp phn ng ch to mui sunfat. Dng ny ta cn: + NO3- phn ng ht + Khi lng mui bng khi lng ca kim loi v SO42- II.3.2. Tnh s mol HNO3 phn ng. (2) Vi nNO3 to mui kim loi = ne nhn = 2 2 2 4 33. 8 10 8NO NO NO N NHNOn n n n n + + + += n.nKL

(vi n l ho tr KL) nNO3 to kh v mui amoni = 2 2 2 4 32 2 2NO NO NO N NHNOn n n n n + + + + Th (2) tr thnh: (2.1) T s mol axit phn ng ta c th tnh c C%, CM, th tch v khi lng dung dch mmui = mkim loi +2 2 2 4 3 262 (3. 8 10 8 ) 96NO NO NO N NHNO SOn n n n n n + + + + + naxit nitric phn ng = nto mui + nto kh v mui amoni naxit nitric phn ng = 2 2 2 4 34 2 10 12 10NO NO NO N NHNOn n n n n + + + + (1.3) www.vietmaths.comSee on vietmaths.com- 7 -III. Nhng bi tp minh ho DNG 1: PHNG PHP BO TON ELECTRON Bi 1: H 2008 KB: Th tch dung dch HNO3 1M long t nht cn dng ho tan hon ton mt hn hp gm 0,15 mol Fe; 0,15 mol Cu (Bit phn ng ch to ra cht kh NO): A. 0,8 litB. 1,0 litC. 1,2 litD. 0,6 lit Li gii: - tng -Da vo LBT electron tnh c nNO -Da vo (2.1) tnh c naxit nitric phn ng = 4nNO Vdd axit phn ng -V th tch dung dch HNO3 cn dng t nht nn Fe ch t n ho tr II. -Gi Vdd HNO3 phn ng 2 0,15 2 0,15431 + == 0,8 (lit) Bi2:HotanmgamFe3O4vodungdchHNO3longdthuckhNOduy nht.NuemkhNOthotratrnviO2va hpth hontontrong nc c dung dch HNO3. Bit th tch oxi phn ng l 0,336 lit (ktc). Gi tr ca m l: A. 34,8gB. 13,92gC. 23,2gD. 20,88g Li gii: - tng -Ch c Fe v O thay i s oxi ho, N khng thay i s oxi ho. -Da vo LBT electron tnh c s mol Fe3O4 (1.3 4Fe On= 4.2On) -Tnh m = 232. 4.2On -Gi 0, 336232 4 13, 92( )22, 4m g = =Bi 3:Cho hn hpgm 4kimloic hotrkhngi:Mg,Ni,Zn,Al cchia lm 2 phn bng nhau: -Phn 1: tc dng vi dung dch HCl d thu c 3,36 lit H2 www.vietmaths.comSee on vietmaths.com- 8 --Phn2:HotanhttrongdungdchHNO3longdthucVlitmtkh khng mu ho nu ngoi khng kh (cc th tch o kc).Gi tr ca V l: A. 2,24 litB. 3,36 litC. 4,48 litD. 5,6 lit Li gii: - tng -Vcckimloichotrkhnginnsmolelectronnhngtrong2th nghim ging nhau s mol electron nhn 2 th nghim cng bng nhau. -Kh khng mu, ho nu ngoi khng kh l NO. -T ta c: 22 3H NOn n = hay 22 3H NOV V = -Php tnh. VNO = V = 23, 36 2, 24( )3lit =Bi 4: Chia m gam hn hp X gm Fe, Al thnh 2 phn bng nhau:-Phn 1: Ho tan hon ton trong dung dch HCl d thu c 7,28 lit H2. -Phn 2:Hotan httrong dung dchHNO3 dthu c 5,6litNO duynht. Cc th tch kh o ktc.Khi lng Fe, Al trong X l: A. 5,6g v 4,05gB. 16,8g v 8,1g C. 5,6g v 5,4g D. 11,2g v 8,1g Li gii: - tng -p dng LBT electron tm s mol Al(x mol); Fe (y mol) trong X -Tc dng vi HCl th Fe t s.o.x.h l +2 cn tc dng vi HNO3 d th Fe t s.o.x.h l +3. + P1: 2.Fe + 3. Al = 2. H2 + P2: 3. Fe +3. Al = 3. NO Fe + Al= NO ( Vit tt s mol)-mFe = 2. 56x; mAl = 2.27y -Php tnh 2x + 3y = 2. 7,28/22,4 x = 0,1 mol x + y = 5,6/22,4y = 0,15 mol Vy: mFe = 2 0,1 56 = 11,2(g) v mAl = 20,1527 = 8,1(g) www.vietmaths.comSee on vietmaths.com- 9 -Bi 5:HotanagamAltrong dung dchHNO3longthythotra 4,48lit hn hp kh NO, N2O, N2 c t l mol ln lt l 1:2:2. Gi tr ca a l: A. 14,04gB. 70,2gC.35,1gD. p s khc Li gii: - tng -Tnh s mol mi kh. -p dng LBT electron tnh nAlmAl = a. -Php tnh - mol (NO) = 1 4, 480, 045 22, 4 = ; mol(N2O) = mol (N2) = (0,2 0,04)/2 = 0,08- mAl = a = 3 0, 04 10 0, 08 8 0, 0827 14, 04( )3g + + =Bi 6: Ly 9,94g hn hp X gm Al, Fe, Cucho tan trong lng d dung dch HNO3 long thy thot ra 3,584 lit kh NO (ktc) duy nht. Khi lng mui khan to thnh: A. 39,7gB. 29,7gC. 39,3gD. 40,18g Li gii: - tng -p dng cng thc (1.2) tnh khi lng mui khan. -Php tnh mmui nitrat = 9,94 + 62 3 3,584/22,4 = 39,7(g) Bi 7: Cho 3 kim loi Al, Fe, Cu tan ht trong 2 lit dung dch HNO3 thu c 1,792 lit (ktc)hnhpkhgmNOvN2OctkhisoviHel9,25.NngCM ca dung dch HNO3 ban u l (Bit He = 4) A. 0,28MB.1,4MC. 1,7MD. 1,2M Li gii: - tng - Thh Mta nhm c mol (NO) = mol (N2O) - p dng cng thc (2.1) tnh mol (HNO3 phn ng) CM (HNO3). -Php tnh - mol (NO) = mol (N2O) = 1 1, 7920, 042 22, 4 =- 4 0, 04 10 0, 040, 28( )2MC M + = = www.vietmaths.comSee on vietmaths.com- 10 - Bi 8: H 2007 KA: Ho tan hon ton 12g hn hp Fe v Cu ( t l mol 1:1) bng axit HNO3 thu c V lit hn hp kh X gm NO v NO2 v dung dch Y (ch cha 2 mui v axit d). T khi ca X so vi H2 l 19. Gi tr ca V l: A. 2,24B. 3,36C. 4,48D. 5,6 Li gii: - tng -Tnh mol(Fe) v mol(Cu) - Thh Mta nhm c mol (NO) = mol (NO2) = a mol- p dng LBT electron tnh Vhh kh = 22,4 2 a -Php tnh -Vhh kh

12(2 3)64 5622, 4 2 5, 6( )4lit ++= =Bi9:HYDcHN2000.Hotan4,431ghnhpAlvMgtrongdungdch HNO3longthu c dung dchX(khngcha muiamoni)v 1,568lit(ktc) hn hp kh khng mu c khi lng 2,59g trong c mt kh ho nu trong khng kh. S mol HNO3 phn ng l: A. 0,51B. 0,455C. 0,55D. 0,49 Li gii: - tng- kh khng mu ho nu ngoi khng kh kh NO - T hh Mkh suy ra kh khng mu cn li l N2O v mol (NO) = mol (N2O). - Tnh s mol mi kh (a mol) - T (2.1) tnh s mol HNO3 phn ng = 4 nNO + 10 2NOn=14 a -Php tnh - 2, 59 22, 4371, 568hh M= = mol (NO) = mol (N2O)-mol (HNO3) = 1, 568(4 10) 0, 49( )2 22, 4mol + = Bi 10: Ho tan hon ton m gam hn hp gm 3 kim loi bng dung dch HNO3 thu c1,12lit hn hpkhX(kc)gmNO2vNO.TkhihicaXsoviH2l 18,2. Th tch dung dch HNO3 37,8% (d = 1,242g/ml) cn dng l www.vietmaths.comSee on vietmaths.com- 11 - A. 20,18 mlB. 11,12 mlC. 21,47 mlD. 36,7 ml Li gii: - tng- Gii h phng trnh tm mol mi kh (NO: x mol; NO2: y mol) - p dng cng thc (2.1) tnh mol HNO3 phn ng. - Tnh th tch dung dch HNO3 phn ng. -Php tnh x+ y = 1,12/22,4 x = 0,03 30x + 46y = 18,2 2 0,05y = 0,02- Vdd axit phn ng

(4 0, 03 2 0, 02) 6337,8%21, 47( )1, 242ml + = =Bi 11: Ho tan 15,2g hn hp A gm Fe v Cu vo 500ml dung dch HNO3 long d thu c 2,24 lit kh NO (00C v 2 at). trung ho axit cn d phi dng va 80g dung dch NaOH 20%. Nng mol/l ban u ca dung dch HNO3 ban u l:A. 3,6MB. 1,8MC. 2,4MD. p s khc Li gii: - tng-Tnh mol kh NO theo cng thc PV/RT -p dng cng thc (2.1) tnh mol HNO3 phn ng vi kim loi. -Tnh mol HNO3 d = nNaOH tnh mol HNO3 ban u CM -Php tnh CM dd axit nitric = 2, 24 2 80 20%40, 082 273 402, 4( )0, 5M +=Bi12:H2009KA:Cho3,024gmtkimloiMtanhttrongdungdchHNO3 long thu c 940,8 ml kh NxOy (ktc, sn phm kh duy nht) c t khi so vi H2 l 22. Kh NxOy v kim loi M l: A. NO v MgB. N2O v FeC. NO2 v AlD. N2O v Al Li gii: - tng- T Mkh kh N2O www.vietmaths.comSee on vietmaths.com- 12 - -LBT electron tm MKL = f(n) vi n l ho tr ca kim loi ( 1 3 n s s ) -Xc nh kim loi. -Php tnh - 3, 02490, 9408822, 4KLM nn= = Chn n = 3 v MKL = 27 (Al) Bi 13: Ho tan hon ton 2,6g kim loi X bng dung dch HNO3 long, lnh thu c dung dch Y. Cho Y tc dng vi dung dch NaOH un nng thy thot ra 224 cm3 kh (kc). Kim loi X l: A. Mg B. AlC. ZnD. Fe Li gii: - tng-Dung dch sau phn ng tc dng vi NaOH c kh nn sn phm kh phi c mui NH4NO3 4 3 3NHNO NHn n = -LBT (e) tm mol R = f(n) vi n l ho tr ca kim loi ( 1 3 n s s ). - Tm MKL = f(n) Chn n thch hp v xc nh R. -Php tnh - 2, 632, 50, 224822, 4KLM nn= = Chn n = 2 v MKL = 65 (Zn) Bi 14: Ho tan 15,6g hn hp kim loi R c ho tr khng i vo dung dch HNO3 long d. Khi phn ng kt thc thu c 896ml kh N2. Thm vo dung dch mi thu c mt lng dung dch NaOH nng d c 224ml mt cht kh. (Cc th tch kh o ktc). Kim loi R l: A. ZnB. CuC. AlD. Mg Li gii: - tng-Dung dch sau phn ng tc dng vi NaOH c kh nn sn phm kh phi c mui NH4NO3 4 3 3NHNO NHn n = -LBT electron tm mol R = f(n) vi n l ho tr ca kim loi ( 1 3 n s s ). - Tm MKL = f(n) Chn n thch hp v xc nh R. www.vietmaths.comSee on vietmaths.com- 13 - -Php tnh 15, 632, 50,896 0, 22410 822, 4 22, 4KLM nn= = + Chn n = 2 v MKL = 65 (Zn) Bi15:Hotan 4,95g hn hpXgmFevKimloiRc hotrkhng itrong dungdchHCldthuc4,032litH2.Mtkhc,nuhotan4,95ghnhptrn trong dung dch HNO3 d thu c 0,336 lit NO v 1,008 lit N2O. Tm kim loi R v % ca n trong X:(Cc th tch kh o ktc). A. Mg v 43,64% B. Zn v 59,09% C. Cr v 49,09%D. Al v 49,09% Li gii: - tng - Gi Fe (x mol) v R (y mol); ho tr R l n (1 3 n s s ) -LBT electron Gii h phng trnh tm x v ny. -T khi lng hn hp v khi lng Fe mR MR = f(n). - Chn n thch hp v xc nh R. -Php tnh 2x + ny=2 4,032/ 22,4x = 0,045 3x + ny =3 0,336/22,4 + 8 1,008/22,4 ny = 0,27 - 4, 95 0, 045 5690, 27KLM nn = = Chn n = 3 v MKL = 27 (Al) Bi16:Cho3,6gMgtanhttrongdungdchHNO3longdsinhra2,24litkhX (sn phm kh duy nht ktc), Kh X l: A. N2OB. NO2C. N2D. NO Li gii: - tng- Gi s 1 mol X trao i n mol electron - p dng LBT electron tm n v chn kh X. -Php tnh www.vietmaths.comSee on vietmaths.com- 14 - 3, 622432, 2422, 4n= = X l kh NO.Bi 17: H 2009 KA: Ho tan 12,42g Al bng dung dch HNO3 long d c dung dch X v 1,344 lit (ktc) hn hp kh Y gm N2O v N2, t khi ca Y so vi H2 l 18. C cn dung dch X thu c bao nhiu gam mui khan: A. 106,38gB. 34,08gC. 97,98gD. 38,34g Li gii: - tng- Da vohh Mnhm nhanh s mol mi kh.- Chng minh: e nhng > e nhn to kh phn ng to mui amoni. - m mui khan = 3 3 4 3( ) Al NO NHNOm m +-Php tnh - ne nhng = 3 12,42/27 = 1,38 > (10 + 8) 1,344/(2 22,4) = 0,54 - mmui khan thu c = 12, 42 1, 38 0, 54(27 62 3) (18 62) 106, 38( )27 8g + + + =Bi 18: Ho tan hon ton 8,4g Mg vo 1 lit dung dch HNO3 va . Sau phn ng thu c 0,672 lit kh N2 (ktc) v dung dch Y. C cn dung dch Y thu c 55,8g mui khan. Nng mol/l ca dung dch HNO3 dng: A. 0,76MB. 0,86MC. 0,96MD. 1,06M Li gii: - tng-SosnhkhilngmuiMg(NO3)2vkhilngmuikhanthuc,CMR phn ng c to mui NH4NO3. - Tnh s mol NH4NO3 - mol HNO3 phn ng= to mui kim loi + to kh N2 + to mui NH4NO3 -Php tnh -Khi lng Mg(NO3)2 = 8, 4(24 2 62) 51, 8( ) 55, 8( )24g g + = < to mui NH4NO3 www.vietmaths.comSee on vietmaths.com- 15 - -CM HNO3 phn ng =8, 4 0, 672 55, 8 51, 82 2 224 22, 4 800, 86( )1M + + = Bi 19: H 2010 KB: Nung 2,23g hn hp X gm 3 kim loi Fe, Al, Zn trong oxi sau mt thi gian thu c 2,71g hn hp Y. Ho tan ht Y vo dung dch HNO3 d c 0,672 lit kh NO kc (sn phm kh duy nht). S mol HNO3 phn ng: A. 0,12B. 0,14C. 0,16D. 0,18 Li gii: - tng-p dng LBTKL tnh khi lng O s mol O (a mol) -Trong bi ton ny, cc kim loi, O, N thay i s o.x.h -p dng LBT electron tm s mol electron nhng (chnh l s mol HNO3 to mui) - S mol HNO3 phn ng = to mui + to kh-Php tnh S mol HNO3 phn ng =[2, 71 2, 23 0, 6722 316 22, 4 + ] 0, 6720,18( )22, 4mol + = DNG 2: PHNG PHP QUI I Bi 1: H KB 2007: Nung m gam bt Fe ngoi khng kh thu c 3g hn hp cht rn X. Ho tan ht hn hp X trong dung dch HNO3 d thu c 0,56 lit kh NO l sn phm kh duy nht (kc). Gi tr ca m l: A. 2,22B. 2,52C. 2,32D. 2,62 Li gii: - tng-Qui i 3g hn hp X thnh 3g hn hp Fe (x mol) v O (y mol) -T khi lng hn hp v p dng phng php bo ton electron lp h. -Php tnh 56x + 16y = 3 x = 0,045 3x 2y= 3 0,56/22,4 y = 0,03 www.vietmaths.comSee on vietmaths.com- 16 - - mFe = 56x = 56 0,045 = 2,52g Bi 2: t chy 5,6g bt Fe trong bnh ng O2 thu c 7,36g hn hp X gm 4 cht rn.Hotan hnhpXbngdung dchHNO3thucV ml(ktc)hn hpkhY gm NO v NO2. T khi ca Y so vi H2 bng 19. Th tch V l: A. 672B. 336 C. 448D. 896 Li gii: - tng-Davohh M nhmnhanhtlsmolmikh.(Trnghpnysmol2kh bng nhau) nhn hp = 2nNO - Qui i 7,36g hn hp X thnh Fe (x mol) v O (y mol) - BTKL tnh khi lng O t tnh s mol Fe v O -pdngLBTelectron(3.Fe 2.O= 3.NO+1.NO2)tnhs molNOvNO2 th tch hn hp hn hp. -Php tnh Vhh kh = 5, 6 7, 36 5, 63 256 162 22, 4 0, 896( ) 896( )3 1lit ml = =+ Bi 3: 6,72g Fe trong khng kh thu c m gam hn hp X gm 4 cht rn. ho tan X cn dng va ht 255ml dung dch HNO3 2M thu c V lit kh NO2 (sn phm kh duy nht kc). Gi tr ca m v V l: A. 8,4 v 3,360B. 10,08 v 3,360C. 8,4 v 5,712D. 10,08 v 5,712 Li gii: - tng-p dng cng thc (2.1) tnh s mol NO2 th tch NO2 -p dng LBT electron (3.Fe 2.O = 1. NO2) s mol O (a mol) -m = 6,72 + 16.a -Php tnh -VNO = 6, 7222, 4 (2 0, 255 3 ) 3, 36( )56lit =- 6, 723 0,15566, 72 16 10, 08( )2m g = + =www.vietmaths.comSee on vietmaths.com- 17 - Bi 4: H 2008KA: Cho 11,36g hn hp X gm: Fe; FeO; Fe2O3 v Fe3O4 phn ng ht vi dung dch HNO3 long d c 1,344 lit kh NO (kc) v dung dch Y. Khi lng mui khan thu c khi c cn dung dch Yl: A. 49,09gB. 35,50gC. 38,72gD. 34,36g Li gii: - tng - Qui i X thnh 11,36g hn hp Fe (x mol) v O (y mol) - LBT electron (3.Fe 2.O = 3.NO) kt hp vi mhn hp X gii h tm x, y. - Khi lng mui Fe(NO3)3 = 242x. -Php tnh -56x + 16y = 11,36 x = 0,16 3x 2y = 3 1,344/22,4y = 0,1 -Khi lng Fe(NO3)3 = 242 0,16 = 38,72(g) Bi 5: Ho tan ht m gam hn hp Fe; FeO; Fe3O4 trong dung dch HNO3 c nng d c 448ml kh NO2 (kc). C cn dung dch sau phn ng c 14,52g mui. Gi tr ca m: A. 3,36B. 4,64C. 4,28D. 4,80 Li gii: - tng- L bi ton ngc so vi bi 4. - Qui i hn hp v Fe (x mol) v O (y mol). Vi mol Fe(NO3)3 = mol Fe=x - Da vo khi lng mui tm x. - Da vo LBT electron (3.Fe 2.O = 1. NO2)y = 23.2Fe NO - m = 56x + 16y -Php tnh 14, 52 0, 448314, 52 242 22, 456 16 4, 64( )242 2m g = + =Bi 6: Cho m gam hn hp X gm Fe v Fe3O4 tc dng vi 200ml dung dch HNO3 3,2M. Sau phn ng c 2,24 lit kh NO (kc) duy nht v cn li 1,46g kim loiwww.vietmaths.comSee on vietmaths.com- 18 - khng tan. Gi tr ca m: A. 17,04B. 19,20C. 18,50D. 20,50 Li gii: - tng- Qui i X thnh Fe (x mol) v O (y mol) - V kim loi d nn Fe ch t Fe+2. - p dng cng thc (2) tm s mol HNO3 to mui s mol Fe (x mol) - LBT electron (2.Fe 2.O = 3.NO) s mol O = y = 2. 3.2Fe NO - Tm m = 1,46 + 56x + 16y. -Php tnh - 2, 24 2, 24 2, 240, 2 3, 2 0, 2 3, 2 322, 4 22, 4 22, 41, 46 56 16 18, 5( )2 2m g = + + =Bi 7: Cho 5,584g hn hp Fe v Fe3O4 tc dng va vi 500ml dung dch HNO3 long. Sau khi phn ng hon ton thu c 0,3136 lit kh NO duy nht v dung dch X. Nng dung dch HNO3 phn ng l:A. 0,472MB. 0,152MC. 3,040MD. 0,304M Li gii: - tng-Qui i hn hp thnh 5,584g Fe(x mol) v O (y mol) -LBT electron (3.Fe 2.O = 3.NO) kt hp vi mhn hp tm x, y -p dng cng thc (2) tm s mol HNO3 phn ng CM -Php tnh 56x + 16y = 5,584 x = 0,074 3x 2y = 30,3136/22,4y = 0,09 - 0,31363 0, 07422, 40, 472( )0, 5MC M += =Bi8:H2009KB:Cho61,2ghnhpCuvFe3O4tcdngvidungdchHNO3 long, un nng v khuy u. Sau khi phn ng xy ra hon ton thu c 3,36 lit kh NOduynht(ktc), dungdchYvcnli2,4gkimloi.CcndungdchYthu c m gam mui khan. Gi tr ca m: www.vietmaths.comSee on vietmaths.com- 19 - A. 151,5gB. 97,5gC. 137,1gD. 108,9g Li gii: - tng-QuiihnhpthnhCu(xmol);Fe(ymol)vO(4y/3mol)smol Fe3O4 l y/3 - V kim loi Cu d nn Fe t n Fe+2 - LBT electron (2.Cu + 2.Fe 2.O = 3.NO) kt hp vi khi lng hn hp, gii h tm x, y. - mmui khan = 3 2 3 2( ) ( ) Cu NO Fe NOm m + = 188x + 180y -Php tnh -64x + 232y/3 = 61,2 2,4x = 0,375 2x+ 2y 8y/3 = 30,15 y = 0,45 - mmui khan = 188x + 180y = 188 0,375 + 180 0,45 = 151,5(g) Bi9:Cho13,92ghnhpCuvmtoxitsttcdngvidungdchHNO3long c 2,688 lit kh NO duy nht (kc) v 42,72g mui khan. Cng thc oxit st: A. FeOB. Fe2O3 C. Fe3O4 D. khng xc nh Li gii: - tng- Qui i hn hp thnh Cu (a mol); Fe (b mol); O (c mol) - p dng LBT electron (2.Cu + 3.Fe 2.O = 3.NO) kt hp vi khi lng hn hp v khilng mui,gii h phng tnh tm a, b, c.- Gi CTTQ ca oxit l FexOy, tm t l x : y = b : cCng thc oxit st. -Php tnh - 64a + 56b + 16c = 13,92a = 0,15 2a + 3b 2c = 3 2,688/22,4 b = 0,06 188a + 242b = 42,72c = 0,06 - V b : c = 0,06 : 0,06 = 1 : 1 nn oxit l FeO (p n A). Bi10:ChomgamhnhpXgmFeO;CuOvFe3O4csmolbngnhautc dng hon ton vi lng va 250ml dung dch HNO3 c dung dch Y v 3,136 lit hn hp NO2; NO (ktc), t khi ca hn hp kh so vi H2 l 20,143. Gi tr ca m v nng mol/lca dung dch HNO3 phn ng l:A. 46,08g v 7,28MB. 23,04g v 7,28Mwww.vietmaths.comSee on vietmaths.com- 20 - C. 23,04g v 2,10MD. 46,08gv 2,10M Li gii: - tng- Gi s mol mi oxit l x. Qui i hn hp thnh Fe (4x); Cu (x); O (6x) - Gii h phng trnh tm s mol NO2 v NO. - LBT electron (3.Fe + 2.Cu 2.O = 3.NO + NO2), gii phng trnh tm x. - m = (72 + 80 + 232)x = 384x.- mol HNO3 phn ng = to mui + to kh = (12x + 2x) + 0,14 CM -Php tnh -a + b = 3,136/22,4 a = 0,09 46a + 30b = 20,133 2 3,136/22,4 b = 0,05 -12x + 2x 12x = 3. 0,05+ 0,09 x = 0,12 -m = (72 + 80 + 232)x = 384 0,12 =46,08(g) -Nng mol HNO3 phn ng = 14 0,14 14 0,12 0,147, 28( )0, 25 0, 25xM+ += =Bi 11: Ho tan hon ton 30,4g hn hp rn X gm Cu, CuS, Cu2S v S bng dung dchHNO3thotra20,16lit khNOduynht(kc)vdungdch Y.ThmBa(OH)2 d vo dung dch Y thu c bao nhiugam kt ta: A. 81,55gB. 29,40gC. 110,95gD. 115,85g Li gii: - tng- Qui i hn hp thnh Cu (x mol); S (y mol) - LBT electron (2.Cu + 6.S = 3.NO) v khi lng hn hp, gii h tm x, y. - Khi lng kt ta = 2 4( )98 233CuOH BaSOm m x y + = +-Php tnh -2x + 6y = 3 20,16/22,4x = 0,3 64x + 32y = 30,4 y = 0,35 - mkt ta = 98 0,3 + 233 0,35 = 110,95(g). Bi 12: Hn hp X gm Zn; ZnS; S. Ho tan 17,8g hn hp X trong HNO3 nng d thu c V lit kh NO2 duy nht (kc) v dung dch Y. Thm t t dung dch Ba(OH)2 d vo dung dch Y thu c kt ta nng 34,95g. Gi tr ca V: A. 8,96B. 20,16C. 22,40D. 29,12 www.vietmaths.comSee on vietmaths.com- 21 - Li gii: - tng- Dng bi ton ngc so vi bi 11. - V Zn(OH)2 lng tnh nn kt ta ch l BaSO4 4 S BaSOn n = mS. - T mhh mZnnZn D LBT electron (2.Zn + 6.S = 1. NO2)tm 2NOn 2NOV -Php tnh 234, 9517, 8 3234, 9523322, 4 (2 6 ) 29,12( )65 233NOV lit = + =Bi 13: Cho lung kh H2 i qua ng s ng m gam Fe2O3 nung nng. Sau mt thi gian thu c 13,92g hn hp X gm 4 cht. Ho tan ht X bng dung dch HNO3 c nng, d c 5,824 lit NO2 (kc, sn phm kh duy nht). Gi tr ca m: A. 16B. 32C. 48D. 64 Li gii: - tng-QuiihnhpXthnh13,92gFe(xmol)vO(ymol)SmolFe2O3 ban u l x/2. - p dng LBT electron (3.Fe 2.O = 1.NO2) kt hp vi khi lng hn hp X, gii h phng trnh tm x, y. - m = 160x/2 = 80x -Php tnh 56x + 16y = 13,92x = 0,2 3x 2y = 5,824/22,4 y = 0,27 - m = 80 0,2 = 16(g) Bi 14: Cho 0,15 mol CuFeS2 v 0,09 mol Cu2FeS2 tc dng vi dung dch HNO3 d thu c dung dch X v hn hp kh Y gm NO v NO2. Thm BaCl2 d vo dung dch X thu c m gam kt ta. Mt khc, nu thm dung dch Ba(OH)2 d vo dung dchX,lykttanungtrongkhngkh nkhilngkhngithucagam cht rn. Gi tr ca m v a: www.vietmaths.comSee on vietmaths.com- 22 - A. 111,84g v 157,44gB. 112,84g v 157,44g C. 111,84g v 167,44gD. 112,84g v 167,44g Li gii: - tng- Qui i hn hp ban u v Cu, Fe, S Tnh c s mol Cu, Fe, S - Thm dung dch BaCl2 d vo X th kt ta l BaSO4 vi 4 BaSO Sn n = mkt ta= 233nS. Thm dung dch Ba(OH)2 d vo X th kt ta l BaSO4, Cu(OH)2, Fe(OH)3 Nung kt ta thu c cht rn l BaSO4; CuO; Fe2O3

a = 233nS + 80nCu + 80nFe = m + 80nCu + 80nFe

-Php tnh - 4(0,15 2 0, 09 2) 233 111, 84( )BaSOm m g = = + =- 2 340,15 0,09111,84 (0,15 2 0,09) 80 160 157,44( )2BaSO CuO Fe Oa m m m g+= + + = + + + =Bi 15: H Dc HN 2001: Hn hp X gm FeS2 v MS c s mol nh nhau, M l kim loi c ho tr khng i. Cho 6,51g X tc dng hon ton vi lng d dung dch HNO3unnngthucdungdchA1v13,216lithnhpkhA2(kc)ckhi lng 26,34g gm NO2 v NO. Thm mt lng BaCl2 d vo dung dch A1 thy to thnh m1 gam kt ta trng trong dung dch d axit trn. Kim loi M v gi tr m1 l: A. Cu v 20,97gB. Zn v 23,3g C. Zn v 20,97g D. Mg v 23,3g Li gii: - tng- Gi s mol mi cht trong X l x mol - Qui i X thnh 6,51g hn hp Fe (x mol);M (x mol); S (3x mol) - Gii h phng trnh tnh s mol NO2 (a mol); NO (b mol) -p dng LBTelectron(3.Fe+ 2.M + 6.S= 3.NO+ 1.NO2)kt hp vikhi lng X tm M.-Kt ta trng ch l BaSO4 vi: 4 BaSO Sn n = = 3x4 1233 3 699BaSOm m x x = = =www.vietmaths.comSee on vietmaths.com- 23 - -Php tnh - a + b = 13,216/22,4 = 0,59a = 0,54 46a + 30b = 26,34b = 0,05 -56x + 96x + Mx = 6,513x + 18x + 2x = 3 0,05 + 0,54 = 0,69 M =65 (Zn) v m1 = 6990,03 = 20,97(g) DNG 3: KIM LOI TC DNG VI HN HPHNO3 V H2SO4 Bi 1: Ho tan hon ton 19,2g kim loi M trong hn hp dung dch HNO3 v H2SO4 c nngthu c 11,2 lit kh X gm NO2 v SO2 c t khi so vi metan l 3,1. Kim loi M l: A. MgB. AlC. FeD. Cu Li gii: - tng- Gii h phng trnh tm s mol NO2 (a mol) v SO2 (b mol) - LBT electron (n.M = 1.NO2 + 2.SO2) M = f(n) vi n 1 3 n s s ) - Xc nh M. -Php tnh -a + b = 0,5a = 0,4 46a + 64b = 0,53,1 16b = 0,1 - M = 19, 2320, 6nn= Chn n = 2 v M = 64 (Cu) Bi 2:Hotan 0,1 molCu vo120ml dung dchXgmHNO3 1MvH2SO4 0,5M. Sau khi phn ng kt thc thu c V lit kh NO duy nht. Gi tr ca V: A. 1,344 litB. 1,49 litC. 0,672 litD. 1,12 lit Li gii: - tngwww.vietmaths.comSee on vietmaths.com- 24 - -Tnh nhanh nCu; Hn+; 3NOn -Vit PT ion thu gn v xc nh cht no (Cu; H+; NO3-) phn ng ht -Tnh VNO -Php tnh -nCu = 0,1; Hn+ = 0,24; 3NOn = 0,12 -3Cu + 8H+ + 2NO3- 3Cu2+ + 2NO + 4H2O -T PT ta c 33 8 2NOCu Hnnn+> < H+ phn ng ht -VNO = 122, 4 0, 24 1, 344( )4lit =Bi 3: Dung dch A ch cha cc ion H+; NO3-; SO42-. em ho tan 6,28g hn hp B gm 3 kim loi c ho tr ln lt l I, II, III vo dung dch A thu c dung dch D v 2,688litkhXgmNO2vSO2.CcndungdchDcmgammuikhan,bit rng kh X c t khi so vi H2 l 27,5. Gi tr ca m l: A. 15,76gB. 16,57gC. 17,56gD. 16,75g Li gii: - tng-Nhm nhanh thy s mol NO2 v SO2 bng nhau. - p dng cng thc (1.3) tnh khi lng mui thu c. -Php tnh -mol (NO2) = mol (SO2) = 0,06 - mmui = 6,28 + 62 0,06 + 96 0,06 = 15,76(g) Bi 4: Ho tan hn hp A gm Cu v Ag trong dung dch HNO3 v H2SO4 thu cdung dch B cha 7,06g mui v hn hp G gm 0,05 mol NO2 v 0,01 mol SO2. Khilng hn hp A bng: A. 2,58gB. 3,06gC. 3,00gD. 2,58g Li gii: - tng- L bi ton ngc ca bi 3. - p dng cng thc(1.3) tnh khi lng hn hp A. -Php tnh www.vietmaths.comSee on vietmaths.com- 25 - - mhhA = 7,06 - 62 0,05 96 0,01 =3,00(g) Bi 5: Ho tan ht hn hp gm x mol Fe v y mol Ag bng dung dch hn hp HNO3 v H2SO4 thy c 0,062 mol kh NO v 0,047 mol SO2 thot ra. em c cn dung dch sau phn ng th thu c 22,164g hn hp cc mui khan. Gi tr ca x v y l: A. 0,07 v 0,02B. 0,09 v 0,01 C. 0,08 v 0,03D.0,12 v 0,02 Li gii: - tng-p dng LBT electron v cng thc (1.3) gii h phng trnh tm x, y. -Php tnh - 56x + 108y = 22,164 62 30,062 - 96 0,047 x = 0,09 3x + y = 3 0,062 + 2 0,047y = 0,01 Bi 6: Ho tan ht 10,32g hn hp Ag, Cu bng lng va 160ml dung dch gm HNO3 1M v H2SO4 0,5M thu c dung dch X v sn phm kh NO duy nht. C cn dung dch A thu c khi lng mui khan l: A. 22,96gB. 18,00gC. 27,92g D. 29,72g Li gii: - tng - Tnh s mol: H+; NO3-; SO42- - T phng trnh ion ca Cu, Ag vi H+ v NO3- ta thy: 34.H NOn n+ = - Suy ra, H+ ht, NO3- d mmui khan =24 3KLSO NOdum m m + + -Php tnh - H+ = 0,32; NO3- = 0,16; SO42- = 0,08 - mol (NO3- phn ng) = 10, 32 0, 08( )4mol = . -mmui khan = 10,32 + (0,16 0,08).62 + 0,08. 96 = 22,96(g). Bi7:HotanbtFevo200mldungdchNaNO3vH2SO4.nphnnghon ton thu c dung dch A v 6,72 lit hn hp kh X gm NO v H2 c t l mol 2:1 v 3g cht rn khng tan. Bit dung dch A khng cha mui amoni. C cn dung dch A thu c khi lng mui khan l: A. 126gB. 75gC. 120,4gD. 70,4g Li gii: www.vietmaths.comSee on vietmaths.com- 26 - - tng: - Tnh s mol: H+; NO3-; NO v H2 - Kim loi d nn phn ng ch to mui Fe2+ v H+, NO3- phn ng ht. - Dung dch sau phn ng ch gm Fe2+; Na+; SO42- - 3NONa NOn n n+ = =

- 21, 5Fe NO Hn n n = +- 234. 2.HH NOn n n+ = + 22 4412HSOSO Hn n n += = -Php tnh: mmui khan = 0,2. 23 + (0,3 + 0,1) .56 + 0,5 . 96 = 75g www.vietmaths.comSee on vietmaths.com- 27 - IV. Ni dung thc nghim s phm IV.1. Mc ch thc nghim s phm Mcchthc nghimsphmnhm nhgihiu quca phngphp a ra thng qua h thng cu hi trc nghim di dng mt bi kim tra 60 pht i vi hc sinh lp 11. IV.2. Nhim v thc nghim s phm - Dng h thng cu hi trc nghim son tho da trn nhng php a, trnh by trc HS trong thi lng 3 tit. Sau tin hnh kim tra, nh gi. - Phn tch cc cu hi, nh gi mc kh ca vn nu ra. -S b nhgikh nngtipthukinthc ho hcca hcsinhvktqu qu trnh dy hc. - nh gi thi ca hc sinh. IV.3. Phng php thc nghim s phm Thc nghims phmctin hnh vi180 hc sinh/4 lptrng THPT Chng M B Chng M B - H Ni.- m bo tnh trung thc v ngn nga hin tng sao chp gia nhng hc sinh ngi gn nhau, cu hi v cu tr li c xo trn thnh 4 . - Mt hc sinh c pht mt v mt phiu lm bi, thi gian lm bi l 60 pht. -kinca mtsgiovin ctham khothng quatrao itrctipv gin tip qua phiu tham kho kin. - kin ca gio vin v cc s liu c phn loi v thng k. - Phiu tham kho kin (xem phn ph lc). - Ni dung kim tra v phiu lm bi : www.vietmaths.comSee on vietmaths.com- 28 - PHIU THC NGHIM S PHM Gii nhanh bi ton axit nitric thng gp trn my tnh H, tn th sinh:...................................................... Trng/Lp............................. Cc em vui lng gii nhanh cc bi ton sau y trn my tnh trong thi gian 60 pht, sau chn p n ca mnh bng cch t en vo p n tng ng./. 1234567891011121314151617181920 A B C D BI: Cu 1: Cho 13,92g Fe3O4 tc dng hon ton vi dung dch HNO3, sau phn ng thu c dung dch X v 0,448 lit kh NxOy (sn phm kh duy nht kc). Khi lng HNO3 nguyn cht tham gia phn ng l: A. 17,64gB. 33,48gC. 35,28gD. 12,60g Cu 2: Cho 11,8g hn hp Al, Cu phn ng vi dung dch HNO3, H2SO4 d thu c 13,44lithnhpkhSO2,NO2ctkhisoviH2l26.Khilngmuitora trong dung dch l: A. 50,00gB. 61,20gC. 56,00gD. 55,80g Cu 3: Ho tan hon ton 19,2g Cu bng dung dch HNO3, ton b lng kh NO (sn phm kh duy nht) thu c em oxi ho thnh NO2 ri chuyn ht thnh HNO3. Th tch kh oxi (ktc) tham gia vo qu trnh trn l: A. 3,36 litB. 4,48 litC. 6,72 litD. 2,24 lit Cu 4: Ho tan hon ton 25,6g hn hp Fe, FeS, FeS2 v S bng dung dch HNO3 d thucdungdchYvVlitkhNOduynht.ThmdungdchBa(OH)2dvo dung dch Y thu c 126,25g kt ta. Gi tr ca V l: A. 27,58B. 19,04C. 24,64D. 17,92 Cu 5: Ho tan 5,95g hn hp Zn v Al c t l mol 1:2 bng dung dch HNO3 long d thu c 0,896 lit mt sn phm kh duy nht X cha nit. Vy X l: www.vietmaths.comSee on vietmaths.com- 29 - A. NO2B. N2C. NOD. N2O Cu 6: Cho m gam Al phn ng ht vi dung dch HNO3 d thu c 8,96 lit (ktc) hn hp kh NO v N2O c t khi i vi H2 l 18,5. Gi tr ca m l: A. 17,5B. 15,3C. 19,8D. 13,5 Cu 7: Oxi ho chm m gam Fe ngoi khng kh thu c 12g hn hp X gm 4 cht rn. Ho tan hon ton X trong dung dch HNO3 d thu c 2,24 lit kh NO (l sn phm kh duy nht kc). Gi tr ca m l: A. 7,57B. 7,75C. 10,08D. 10,80 Cu8:Hotanhonton45,9gkimloiRbngdungdchHNO3longthuc 26,88 lit (ktc) hn hp kh N2O v NO, trong s mol NO gp 3 ln s mol N2O. Kim loi R l: A. ZnB. AlC. MgD. Fe Cu 9: Oxi ho hon ton 0,728g bt Fe ta thu c 1,016g hn hp cc oxit st. Ho tanhontonXbngdungdchHNO3longd.ThtchkhNOkc(snphm kh duy nht) thu c l: A. 22,40mlB. 44,80mlC. 2,24mlD. 33,60ml Cu 10: Ho tan 12,8g Cu trong dung dch HNO3 thy thot ra V lit hn hp kh NO v NO2 (kc), t khi ca hn hp kh i vi H2 l 19. Gi tr ca V l: A. 2,24 litB. 0,448 litC. p s khcD. 4,48 lit Cu 11: Cho 15gam hn hpAlvMgtc dngvi dung dchHNO3 d, nphn ng hon ton thu c dung dch X v 4,48 lt kh duy nht NO ( ktc).C cn dung dch X thu c 109,8 gam mui khan. % s mol ca Al trong hn hp ban u l A. 36%.B. 33,33%.C. 64%. D. 6,67%. Cu 12: Cho 0,05 mol Al v 0,02 mol Zn tc dng va vi 2 lit dung dch HNO3 long, sau phn ng thu c kh khng mu, nh hn khng kh. Phn dung dch em c cn thu c 15,83g mui khan. Nng mol/l ca dung dch HNO3 dng: A. 0,1450MB. 0,1120MC. 0,1125MD. 0,1175M Cu 13: Ho tan m gam hn hp A gm Fe v kim loi M c ho tr khng i trongdung dch HCl d thu c 1,008 lit kh H2 (kc) v dung dch cha 4,575g muikhan. Nu cng ho tan m gam hn hp trn bng dung dch HNO3 c v H2SO4 www.vietmaths.comSee on vietmaths.com- 30 - nhit thch hp th thu c 1,8816 lit hn hp 2 kh (kc) c t khi so vi H2 l25,25. Kim loi M l: A. AlB. FeC. CuD. Zn Cu 14: Hotanhonton hn hpXgm Mg;MgS;Strong dung dchHNO3 c nng d thu c 2,912 lit kh N2 duy nht (kc) v dung dch Y. Thm Ba(OH)2 d vo dung dch Y c 46,55g kt ta. Khi lng hn hp X l: A. 4,8B. 12,0C. 7,2D. 9,6 Cu 15: H 2008 KB: Cho 2,16g Mg tc dng vi dung dch HNO3 d. Sau khi phn ngxyrahontonthuc0,896litkhNO(kc)vdungdchX.Khilng mui khan thu c khi c cn dung dch X: A. 13,92gB. 13,32gC. 8,88gD. 6,52g Cu16:Cho1,35g hnhpgmCu,Mg,Altcdnghtvidung dchHNO3thu c hn hp kh gm 0,01 mol NO v 0,04 mol NO2. Bit phn ng khng to mui amoni. Khi lng mui to ra trong dung dch l: A. 5,96gB. 6,59gC. 5,69gD. 10,08g Cu 17: Hotan 11,76gFebng 200 ml dungdch gmHCl 2,5MvNaNO3 0,5M thu c dung dch B v V (lit) kh NO ( sn phm kh duy nht). Khi lng mui trong dung dch B thu c l: A.26,67gB. 31,25g C. 36,00g D. 25,40g Cu 18: mgam phoi st ngoikhngkh,sau mtthigianst b oxi hothnh hnhpXgm4chtckhilng27,2g.HotanhtXtrong300mldungdch HClamol/lthythotra3,36litkhH2(kc)vdungdchY.Chotipdungdch HNO3ti d vo dung dch Ythu c dungdchZcha hn hpFeCl3, Fe(NO3)3, HNO3 d v 2,24 lit kh NO duy nht thot ra (kc). Gi tr ca m v a ln lt l: A. 22,4g v 2MB. 16,8g v 3M C. 22,4g v 3M D. 16,8g v 2M Cu 19: Dung dch X cha 14,6 gam HCl v 22,56 gam Cu(NO3)2. Thm m (gam) bt st vo dung dch X, sau khi phn ng xy ra hon ton thu c hn hp kim loi c khi lng l 0,5m (gam) v ch to kh NO (sn phm kh duy nht ). Gi tr ca m lA. 9,28B. 20,48C. 14,88D. 1,92 Cu 20: Cho 3,2 gam Cu tc dng vi 100ml dung dch HNO3 0,8Mv H2SO4 0,2M, sn phm kh duy nhtl NO. S gam mui khan thu c l A. 7,90B. 8,84C. 5,64.D. 0,08 www.vietmaths.comSee on vietmaths.com- 31 - IV. 4. Kt qu thc nghim s phm Cch thng k s liu thc nghim S HS t im Xi % HS t im Xi =Tng s HS Da vo % HS t im Xi nh gi trnh HS tng lp v tnh hiu qu ca phng php. Sau khi tin hnh cho HS lm bi kim tra, ti thu phiu lm bi v thng k s liu nh cc bng sau : im Xi Lp 11A1Lp 11A2Lp 11A3Lp 11A4 S HS t im Xi % S HS t im Xi S HS t im Xi % S HS t im Xi S HS t im Xi % S HS t im Xi S HS t im Xi % S HS t im Xi 000,0000,0000,0000,00 100,0000,0000,0012,22 200,0024,4448,88715,56 348,88511,121022,221431,11 4613,33715,561635,561942,22 5715,56920,001328,8948,88 6511,121022,2224,4400,00 7817,78715,5600,0000,00 81022,2248,8800,0000,00 9511,1212,2200,0000,00 1000,0000,0000,0000,00 T kt qu thc nghim trn, ti nhn thy : -Cc cu t 1 n 10, 12, 14, 15, 16 nm trong phng php a ra trn nn HS u c kh nng lm c. -Cu 11 :HSkhng bitchng minhphnng ctomuiamoni haykhng. Binynngiitheoh :Gimol :Al(x) ;Mg(y) ;NH4NO3(z).Lph3 phng trnh ri gii. www.vietmaths.comSee on vietmaths.com- 32 - -Cu 20 :HS d nhm (tnh c khi lng Cu d vo mui) -Cc cu 13, 17, 18, 19 l nhng cu kh, s HS tr li ng t nht : + Cu 18 : HS cha tm ra cha kho gii. Nu c lm, HS ch tm ra c khi lng, cha tm c nng mol/l ca dung dch HCl. Bi c gii n gin nh sau :-Qui i 27,2g X thnh Fe (x) v O (y) -Lp h 2 phng trnh : 56.Fe + 16.O = 27,2 v 3.Fe 2.O = 2.H2 + 3.NO -Tm c x v y khi lng Fe (m = 22,4g) -Bo ton e cho dung dch Y + HNO3 Fe (a) ; FeO (b) ; Fe2O3 (c) a = 0,15; b + 2c = 0,25; a + b = 0,3 b = 0,15; c = 0,05 nHCl = 2.0,15 + 2. 0,15 + 6 . 0,05 = 0,9 mol CM = 0,9/0,3 = 3M -Nhvy, iuchngt stduy,phthincimicaHScn hnch. iu nyhonton ph hpvithctrngcatrng(do uvo, iukin pht trin gio dc cn hn ch). -So snh kt qu ca lp 11A1 ; 11A2 vi 11A3 ; 11A4 ti rt ra 1 s kt lun : + Lp 11A1 v 11A2 (Lp thc nghim) c kt qu cao hn. + Lp 11A3 v 11A4 (Lp i chng) t kt qu thp hn. Nh vy, phng php a ra trn gp 1 phn thc y s nhn thc ca HS v cc dng bi ton thng gp ca axit HNO3 m HS c th gii nhanh trn my tnh. www.vietmaths.comSee on vietmaths.com- 33 - PHN III : KT LUN V KIN NGH T mc ch v nhim v ca ti, tc gi tin hnh nghin cu v gii quyt c mt s ni dung sau: -a ra 1 s cng thc gii nhanh bi tp axit nitric -Su tm mt s bi tp trong cc thi i hc v trn mng gip HS rn luyn k nng gii nhanh trn my tnh. -Thng qua phiu iu tra, bi kim tra, gp g trao i trc tip vi gio vin, ng thi da trn mt s kinh nghim ca bn thn rt ra trong qu ging dy, cc thc mc ca ng nghip, bc u ti hon thin sng kin ca mnh.- Kt qu nghin cu ca ti c th l ti liu tham kho cho cc gio vin v hc sinh lp 11 v 12. V tc gi hi vng, sng kin ny s l ti liu c dng trong tit hc t chn lp 11 (Chng Nit photpho). Tuy nhin do hn ch v mt thi gian v do kinh nghim ca bn thn cn qu t, ngthitrong khunkhcamtsngkinkinhnghimnn tikhngtrnh khi nhng thiu st nn tc gi hi vng s nhn c nhiu kin ng gp ca cc Thy,Citrcvccbnngnghipcthmrngtivarac nhiu hng gii nhanh hn cho bi ton axit nitric hn na. Ti xin chn thnh cm n ! Ngy 20 thng 05 nm 2011 Tc gi L c T ng www.vietmaths.comSee on vietmaths.com- 34 - KIN NH GI V XP LOICA HI NG KHOA HC C S CH TCH HI NG (K tn v ng du)