A. PHN BIT MT S CHT V CI. Nhn bit mt s cation trong dung dch1. Nhn bit cation NH+4- Thm lng d dung dch kim KOH hoc NaOH vo dung dch cha ion amoni s thy c kh mi khai gii phngNH+4+OH NH3+H2O2. Nhn bit Ba2+- nhn bit Ba2+ ta dng cht c cha gc sunfat ( v d H2SO4) , sn phm thu c l kt ta trng khng tanBa2++SO24 BaSO4- C th dng K2CrO4 hoc K2Cr2O7Ba2++CrO24 BaCrO4 ( kt ta vng ti)Ba2++Cr2O27+H2O 2BaCrO4+2H+3. Nhn bit Al3+,Cr3+- 2 cation ny c tnh lng tnh . Khi thm kim vo cho n d th s c hin tng to kt ta v kt ta taAl3++3OH Al(OH)3Al(OH)3+OH [Al(OH)4]4. Nhn bit Fe2+,Fe3+,Cu2+,Ni2+- Thuc c trng nhn bit ion Fe3+ l dung dch cha ion thioxianat SCN , n to kt ta phc mu Fe3++3SCN Fe(SCN)3- Cho dung dch kim NaOH,KOH hoc NH3 vo Fe3+ thu c kt ta mu nu Fe3++3OH Fe(OH)3- Cho kim vo Fe2+ s to kt ta trng , kt ta ny ha nu ngay trong khng khFe2++2OH Fe(OH)24Fe(OH)2+O2+2H2O 4Fe(OH)3- Cc dung dch cha Fe2+ lm mt mu dung dch thuc tm c mt ion H+MnO4+5Fe2++8H+ Mn2++5Fe3++4H2O(tm hng) khng mu- Thuc th c trng ca Cu2+ l dung dch NH3 . Dung dch thuc th u tin to vi ion Cu2+ kt ta Cu(OH)2 mu xanh , sau kt ta b ha tan to phc mu xanh thmCu2++2NH3+2H2O Cu(OH)2+2NH+4Cu(OH)2+4NH3 [Cu(NH3)4]2++2OH- Cc dung dch Ni2+ u c mu xanh l cy , tc dng vi kim to thnh kt ta Ni(OH)2 mu xanh lc v kt ta tan trong NH3 to phc mu xanhNi2++2OH Ni(OH)2Ni(OH)2+6NH3 [Ni(NH3)6]2++2OHII. Nhn bit mt s anion trong dung dch1. Nhn bit NO3- Dng Cu trong mi trng axit => to kh khng mu v ha nu trong khng kh3Cu+2NO3+8H+ 3Cu2++2NO+4H2O2NO+O2 2NO22. Nhn bit SO24- Thuc th c trng cho ion ny l BaCl2 , trong mi trng axit long dBa2++SO24 BaSO4- Dng trong mi trng axit v c mt s loi ion cho kt ta trng ging SO24 nh : CO23,PO34,SO23,HPO24 . Nhng cc kt ta u tan trong mi trng axit3. Nhn bit Cl- Thuc th c trng ca anion ny l Ag+ => to kt ta keo trngAg++Cl AgCl- Cc anion Br v I cng c phn ng tng t . Tuy nhin khc vi AgBr v AgI,AgCl tan trong dung dch NH3 longAgCl+2NH3 [Ag(NH3)2]Cl4. Nhn bit CO23- Dng dung dch axit => to kh khng mu CO2 , nhn CO2 bng cch dn qua dung dch nc vi trongCO23+2H+ CO2+H2OCO2+Ca(OH)2 CaCO3+H2O- C th dng nc vi trong hoc ion Ba2+ => to kt ta trng khng tan trong ncCO23+Ca(OH)2 CaCO3+2OHCO23+Ba2+ BaCO3III. Nhn bit mt s cht kh1. Nhn bit CO2- Nhn CO2 bng cch a qua dung dch nc vi trong hoc dung dch Ba(OH)2 => to kt ta trngCO2+Ca(OH)2 CaCO3+H2OCO2+Ba(OH)2 BaCO3+H2O2. Nhn bit SO2- Kh SO2 khng mu , nng hn khng kh , c mi hc , gy ngt , lm vn c nc vi trong nh CO2- SO2 lm mt mu dung dch Brom v dung dch iot ( mu nu )SO2+Br2+H2O H2SO4+2HBrSO2+I2+2H2O H2SO4+2HI3. Nhn bit Cl2- Cl2 c mu vng lc , nng hn khng kh , mi hc , c , t tan trong nc- Dng giy tm KI v h tinh bt nhn ra Cl2Cl2+KI KCl+I2- I2 to vi h tinh bt hn hp mu xanh4. Nhn bit NO2- NO2 nng hn khng kh , mu nu , c , t tan trong nc , phn ng vi H2O to HNO34NO2+O2+2H2O 4HNO3- Nhn HNO3 bng Cu5. Nhn bit H2S- H2S l kh khng mu , c mi trng thi . H2S d to kt ta sunfua vi nhiu mui ngay c trong mi trng axitCu2++H2S CuS( en) + 2H+Pb2++H2S PbS (en) + 2H+B. BI TP T LUYNCu 1 : C 4 dung dch Al(NO3)3,NaNO3,Na2CO3,NH4NO3 . Ch dng mt dung dch no sau y phn bit cc cht trong dung dch trn ?A. H2SO4 B. NaCl C. K2SO4 D. Ba(OH)2Cu 2 : Ch dng thm mt thuc th no sau y c th phn bit c cc dung dch NaCl,NH4Cl,AlCl3,FeCl2,CuCl2,(NH4)2SO4 ?A. BaCl2 B. Ba(OH)2 C. NaOH D. Qu tmCu 3 : C 5 dung dch ring r , mi dung dch cha 1 cation sau : NH+4,Mg2+,Fe2+,Fe3+,Al3+ ( c nng 0,1M) . Dng dung dch NaOH cho vo tng dung dch trn , c th nhn bit ti a c bao nhiu dung dch ?A. 2 B. 3 C. 1 D. 5Cu 4 : C 5 l cha ha cht mt nhn mi l ng mt dung dch cha cation sau ( nng khong 0,01M) : Fe2+,Cu2+,Ag+,Al3+,Fe3+ . Ch dng 1 dung dch l thuc th KOH c th nhn bit ti a my dung dch ?A. 2 B. 3 C. 1 D. 5Cu 5 : C cc l ha cht khng nhn , mi l cha mt dung dch khng mu sau : Na2SO4,Na2S,Na2CO3,Na3PO4,Na2SO3 . Ch c dng 1 thuc th l H2SO4 nh trc tip vo tng dung dch c th nhn bit dung dch no ?A. Na2CO3,Na2S,Na2SO3 B. Na2CO3,Na2SC. Na2CO3,Na2S,Na3PO4 D. C 5 dung dchCu 6 : C cc dung dch khng mu ng trong cc l ring bit , khng dn nhn : ZnSO4,Mg(NO3)2,Al(NO3)3. phn bit cc dung dch trn c th dng ?A. Qu tm B. NaOH C. Ba(OH)2 D. BaCl2Cu 7 : phn bit cc dung dch MgCl2,ZnCl2,AlCl3,FeCl2,KCl bng phng php ha hc , c th dngA. NaOH B. NH3 C. Na2CO3 D. Qu tmCu 8 : Trong cc thuc th sau : (1) dung dch H2SO4 long , (2) CO2 v H2O ,(3) dung dch BaCl2 , (4) dung dch HCl . Thuc th phn bit c cc cht ring bit CaCO3,BaSO4,K2CO3,K2SO4 lA. (1) v (2) B. (2) v (4) C. (1),(2),(3) D. (1) ,(2) ,(4)Cu 9 : C cc l ring bit cha cc dung dch sau : AlCl3,ZnCl2,FeSO4,Fe(NO3)3,NaCl . Ch dng dung dch no sau y phn bit cc cht trn ?A. Na2CO3 B. Ba(OH)2 C. NH3 D. NaOHCu 10 : C 5 l mt nhn ng 5 dung dch sau : NaOH,MgCl2,CuCl2,AlCl3,FeCl3. S lng thuc th ti thiu dng nhn bit 5 dung dch trn l :A. 3 B. 2 C. 1 D. 0Cu 11 : C cc dung dch ring r sau : AlCl3,NaCl,MgCl2,H2SO4 . nhn bit c 4 dung dch trn ch cn dng 1 thuc th l ?A. NaOH B. BaCl2 C. AgNO3 D. Qu tmCu 12 : Cho cc dung dch : NaCl,AlCl3,Al2(SO4)3,FeCl2,MgCl2,NH4Cl,(NH4)2CO3 . nhn bit cc dung dch trn ch cn dng 1 thuc th l :A. NaOH B. CaCl2 C. Ba(OH)2 D. H2SO4Cu 13 : C 6 dung dch sau : NH4NO3,Al(NO3)3,Pb(NO3)2,FeCl2,HCl,KOH . S lng thuc th ti thiu cn dng nhn bit c cc dung dch trn lA. 3 B. 2 C. 1 D. 0

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