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<p>CHNG III : CHUN OXI HA KH</p> <p>BI 1: 0,1 g mu phn tch cha V, Cr, Mn c phn hy thnh dung dch . Sau khi chha dung dch cc nguyn t tn ti di dng VO 2+ , Cr2O72- , MnO4- .Chun dung dch bng dung dch chun Fe2+ 0,1 M ch ht 50 ml . Ion VO 2+to thnh c chun bng dung dch chun KMnO4 0,01M th ht 5ml . Sau thm vo lng mui pitphtphat to phc vi Mn(III) khi chun Mn 2+ bng dung dch KMnO4 trn , th tch tiu tn ln chun ny l 10ml . Tnh hm lng % mi kim loi trong mu ( V=50,49 ; Cr =52 ; Mn=54,94 ). Bit E 0Fe3+/Fe2+ = 0,77V ; E0VO2+/VO2+=1 V ; E0Cr2O72-/ 2Cr3+= 1,36V ;E0MnO4-/Mn2+= 1,51V</p> <p>BI GII:Tm tt s chun nh sau:</p> <p>V, Cr, MnCh ha VO2+,, Fe2+</p> <p>VO2+, Cr3+, Mn2+MnO4</p> <p>VO2+, Cr3+, Mn2+MnO4</p> <p>VO2+, Cr3+, Mn3+ Trong mu phn tch cha V, Cr , Mn Sau khi ch ho ta c dung dch gm: VO2 2 , Cr2 O7 , MnO4 . * Chun dung dch bng dung dch tiu chun Fe2+ 0,1M ht 50ml.1 Trn Th M L Lp Ha 3B Bi tp ln2</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Ta c:</p> <p>E o Fe3+ / Fe2+E oVO2+ /VO2+</p> <p>= 0,771(V) = 1 (V)</p> <p>E o Cr2O72 / 2Cr3+ E o MnO4 / Mn2+</p> <p>= 1,33 (V) = 1,51 (V)</p> <p>Vy th t phn ng chun xy ra l: + u tin Fe2+ kh MnO4 thnh Mn2+: 5 Fe2+ Fe3+ + e Mn2+ + 4H2O 5Fe3+ + Mn2+ + 4H2O (1)</p> <p> MnO4 + 8H+ + 5e</p> <p>5Fe2+ + MnO4 + 8H+</p> <p>+ Sau : Fe2+ kh Cr2 O7 6 Fe2+2</p> <p>2</p> <p>thnh Cr3+:</p> <p>Fe3+ + e 2Cr 3+ + 7H2O 2Cr 3+ +6Fe3+ + 7H2O</p> <p>Cr2 O7 + 14H+ + 6e6Fe2+ + Cr2 O7 + 14H+ + Cui cng Fe2+ kh VO2 + thnh VO2+: Fe2+ Fe3+ + e2</p> <p>+ VO2 + 2H+ + e</p> <p>VO2+ + H2O Fe3+ + VO2+ + H2O</p> <p>Fe2+ + VO2 + + 2H+ Vy ta c: S lg VO2 + + S lg Cr2 O72</p> <p>+ S lg MnO4 = S lg Fe2+ (S lg: s ng lng gam) (*) (S: s ng lng gam )</p> <p>SVO + + S Cr O 2 + S MnO = S 2 + 2 2 7 4 Fe</p> <p>Gi x, y, z ln lt l s ng lng gam ca V, Cr v Mn trong mu phn tch ban u. Sau khi ch ho ta c dung dch gm: VO2 2 , Cr2 O7 , MnO4 .2 Trn Th M L Lp Ha 3B Bi tp ln2</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Ta c :</p> <p>SVO +2</p> <p>= SV = x</p> <p>S Cr O 2 = 3 SCr = 3y 2 7 S MnO = 5 SMn = 5z 4</p> <p>S Fe2 + =</p> <p>5.10-3 = 5.10-3 (**)</p> <p>Thay vo (*) ta c : x + 3y + 5z =</p> <p>*Sau chun ion VO2+ to thnh bng dung dch chun KMnO4 0,01M ht 5ml. 5 VO2+ + H2O+ VO2 + 2H+ + e</p> <p> MnO4 + 8H+ + 5e</p> <p>Mn2+ + 4H2O Mn2+ +5 VO2 + + 2H+ (2)</p> <p>5VO2+ + H2O + MnO4 Ta c:</p> <p>SVO 2 + = S MnO = 4</p> <p>= 2,5.10-4 = x</p> <p>(***)</p> <p>* Mt khc qu trnh chun VO2+ bng dung dch chun KMnO4 to ra Mn2+ , vy Mn2+ trong dung dch lc ny c tao ra t phng trnh (1) v (2). + (1) : SMn2+ to ra = SMn ban u = z</p> <p>+ (2) : SMn2+ to ra =</p> <p>1S 1 MnO4 chun = 5 5</p> <p>= 5. 10-5</p> <p> Vy tng s ng lng ca Mn2+ trong dung dch lc ny l: SMn2+ = z + 5. 10-5</p> <p>*Chun Mn2+ bng dung dch chun KMnO4 0,01M ht 10ml:3 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>4</p> <p>Mn2+</p> <p>Mn3+ + e MnO4 + 8H+ + 4e</p> <p>Mn3+ + 4H2O</p> <p>4Mn2+ + MnO4 + 8H+ Ta c:</p> <p>4Mn3+ + 4H2O</p> <p>SMn2+ = S MnO4 Hay : z + 5. 10-5 = = 4.10-4 z = 3,5 .10-4 (****)</p> <p>T (**) ; (***) ;(****) ta c h sau : x + 3y + 5z = 5.10-3 x = 2,5 . 10-4 z = 3,5 .10-4 y = 10-3</p> <p>Vy: + SV = x = 2,5.10-4 Khi lng ca V l : mV = SV v = 2,5.10-4 50,94 = 0,0127 (g )</p> <p>Phn trm ca V l : + SCr = y = 10-3 Khi lng ca Cr l : mCr = SCr Phn trm ca Cr l : + SMn = z = 3,5.10-4 Khi lng ca Mn l : mMn =SMn Phn trm ca Mn l :Mn Cr</p> <p>12,7 %</p> <p>= 10-3</p> <p>= 0,052 (g)</p> <p>= 52 %</p> <p>= 3,5.10-4 . 54,94 = 0,0192(g ) ( : ng lng gam )</p> <p>= 19,2%</p> <p>4 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>BI 2: nh phn Fe , Cr ,Ti trong hn hp ngi ta ch ha v thu c 100 mldung dch cha Cr3+ ; Fe3+ ; TiO2+ ( Dung dch A). Ly 20 ml dung dch A cho qua ct kh km v hng dung dch chy ra khi ct vo mt bnh kn c kh quyn khng kh cha oxi .Chun dung dch thu c bng dung dch chun KMnO4 0,02 M th ht 43 ml . Ly 20ml dung dch A na, cho qua ct kh bc , chun dung dch thu c bng dung dch chun K2Cr2O7 0,01M th ht 25,2ml . Ly 20 ml dung dch A thm vo NH3 v H2O2 , un si phn hy ht H2O2 d , lc b kt ta , axt ha nc lc thu c v chun bng dung dch Fe2+ 0,05 M th ht 12,4 ml . Tnh hm lng ( s mg) ca mi kim loi trong dung dich ban u . (Bit Cr =52 ; Fe = 56; Ti = 48 ) .Bit E0TiO2+/Ti3+ = 0,1 V ; E0MnO4-/Mn2+= 1,51V ; E0Cr2O72-/ 2Cr3+= 1,36V ;E0Fe3+/Fe2+ = 0,77V</p> <p>Fe, Cr, Ti</p> <p>BI GII: Tm tt s chun nh sau:</p> <p>Fe3+, Cr3+, TiO2+ Fe3+, Cr3+, TiO2+</p> <p>Fe2+, Cr2+, Ti3+</p> <p>Fe2+, Cr3+, TiO2+</p> <p>Fe3+Cr2O72- TiO2+</p> <p>5 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>Fe , Cr , TiO</p> <p>3+</p> <p>3+</p> <p>2+</p> <p>Fe , Cr , TiO</p> <p>3+</p> <p>3+</p> <p>2+</p> <p>Fe , Cr3+, TiO2+</p> <p>3+</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Ch ho</p> <p>Ct kh km</p> <p>ct kh bc NH3,H2O2</p> <p>KMnO4 K2Cr2O7Fe2+</p> <p>*Xt trong 20ml dung dch A:</p> <p>Ta c:</p> <p>E o Fe3+ / Fe2+</p> <p>= 0,771 (V) ; E o Cr 3+ / Cr 2+ = - 0,408 (V)</p> <p>6 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>E oTiO2+ /Ti3+</p> <p>= 0,099 (V) ; E o Zn2+ / Zn = - 0,763 (V)</p> <p>*Cho 20 ml dung dch A qua ct kh km, khi Cr3+, Fe3+, TiO2+ u b kh:</p> <p>Vy th t phn ng xy ra: + u tin Zn kh Fe3+ v Fe2+ : Fe2+ Zn Zn + Fe3+ Fe2+ + Zn2+ Fe3+ + e Zn2+ + 2e</p> <p>+ Sau Zn kh TiO2+ thnh Ti3+ Zn 2 Zn2+ + 2e Ti3+ + H2O</p> <p>TiO2+ + 2H+ + e</p> <p>Zn + 2TiO2+ + 4H+</p> <p>2Ti3+ + Zn2++ 2H2O</p> <p>+ Cui cng Zn kh Cr3+ thnh Cr2+: Zn 2 Cr3+ +1e Cr2+ Zn + 2Cr3+ 2Cr2+ + Zn2+ Zn2+ + 2e</p> <p>*Xt trong 20ml dung dch A: Gi s ng lng gam ca Fe3+ ,Cr3+, TiO2+ trong 20ml dung dch A ln lt l x, y, z. Ta c : S Fe2+ = S Fe3+ = x S Cr 2+ = S Cr3+ = y STi 3+ = STiO2 + = z7 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Vy dung dch sau khi cho i qua ct kh km l: Fe2+, Cr2+, Ti3+ Chun dung dch thu c bng dung dch chun KMnO4 0,02M ht 43ml. Ta c:</p> <p>E o MnO4 / Mn2+</p> <p>= 1,51 (V) nn th t chun l:</p> <p>+ u tin KMnO4 oxi ho Cr2+ thnh Cr3+ 5 Cr2+ Cr3+ + e Mn2+ + 4H2O</p> <p> MnO4 + 8H+ + 5e</p> <p>5Cr2+ + MnO4 + 8H+</p> <p>5Cr3+ + Mn2+ + 4H2O</p> <p>+ Sau KMnO4 oxi ho Ti3+ thnh TiO2+: 5 Ti3+ + H2O TiO2+ + 2H+ + e Mn2+ + 4H2O Mn2+ + 5TiO2+ + 2H+</p> <p> MnO4 + 8H+ + 5e</p> <p>5Ti3+ + H2O + MnO4 </p> <p>+ Cui cng KMnO4 oxi ho Fe2+ thnh Fe3+: 5 Fe2+ Fe3+ + e Mn2+ + 4H2O</p> <p> MnO4 + 8H+ + 5e</p> <p>5Fe2+ + MnO4 + 8H+</p> <p>5Fe3+ + Mn2+ + 4H2O</p> <p>Ta c: S Fe2+ + S Cr 2+ + STi 3+ = S KMnO4 x+y+z= Ta c : E0Ag+ / Ag = 0,799 V *Ly 20ml dung dch A cho qua ct kh bc th: Khi ch c Fe3+ b kh to thnh Fe2+: Fe3+ + Ag Fe2+ + Ag+ = 4,3.10-3 ( *)</p> <p>8 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Vy dung dch sau khi cho qua ct kh bc gm : Fe2+ , Cr3+, TiO2+. *Sau chun dung dch thu c bng dung dch chun K2Cr2O7 0,01M ht 25,2 ml. Lc ny K2Cr2O7 ch oxi ho Fe2+ thnh Fe3+:</p> <p>6</p> <p>Fe2+</p> <p>Fe3+ + e2</p> <p>Cr2O76Fe2+ + Cr2 O72</p> <p>+ 14H+ + 6e</p> <p>2Cr3+ + 7H2O</p> <p>+ 14H+</p> <p>6Fe3+ +2 Cr3+ + 7H2O</p> <p>Ta c: S Fe2+ = S Cr2O7 2 Hay x = = 1,512.10-3 (**)</p> <p>*Ly 20ml dung dch A, thm vo NH3 v H2O2. Khi ch c Cr3+ b oxi ho thnh 2 Cr2O7 . 3 H2O2 2OH- + 2e</p> <p>2Cr3+ + 14OH- + 6e</p> <p>Cr2 O7 + 7H2O Cr2 O7 + 7H2O2</p> <p>2</p> <p>2Cr3+ + 3H2O2 + 8OH-</p> <p>(1)2</p> <p>Vy dung dch sau khi cho thm NH3 v H2O2 gm: Fe3+ , Cr2 O7 Ta c:E0Cr2O72-/ 2Cr3+= 1,36V</p> <p>, TiO2+</p> <p>*Chun dung dch thu c bng dung dch tiu chun Fe2+ 0,05M ht 12,4ml. Lc ny ch c Cr2O72</p> <p>b Fe2+ kh thnh Cr3+ :</p> <p>6</p> <p>Fe2+</p> <p>Fe3+ + e</p> <p>9 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Cr2O7</p> <p>2</p> <p>+ 14H+ + 6e2</p> <p>2Cr3+ + 7H2O + 14H+ 6Fe3+ + 2Cr3+ + 7H2O</p> <p>6Fe2+ + Cr2 O7</p> <p>Ta c: V: Cr2 O7 Nn :</p> <p>S Cr O 2 = S Fe2+ = 2 72</p> <p>= 6,2 . 10-4 2Cr3+ + 7H2O</p> <p>+ 14H+ + 6e</p> <p>S Cr3+ =</p> <p>1 S Cr2O7 2 62</p> <p>Nhng t phng trnh (1) ta c c 2mol Cr3+ th to ra 1 mol Cr2 O7 Nn : S Cr3+ = 2. y = 2.</p> <p>1 S Cr2O7 2 6</p> <p>Hay</p> <p>1 .6,2 . 10-4 = 2,0667 .10-4 (***) 6</p> <p>T (*) ;(**) ;(***) ta c h sau :</p> <p>x + y + z = 4,3.10-3 x = 1,512.10-3 z = 2,5813.10-3</p> <p>y = 2,0667 .10-4</p> <p>Gi mFe , mCr , mTi ln lt l khi lng ca Fe, Cr, Ti trong hn hp phn tch</p> <p>10 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Trong 20ml ta c: S Fe3+ = x = SFe= 1,512.10-3 mFe= SFe =1,512 .10-3 56 = 84,672.10-3 g = 84,672 mg</p> <p>-4 S Cr 3+ = y = SCr = 2,0667.10</p> <p> mcr= SCr</p> <p>= 2,0667.10-4 52 = 10,746.10-3 g = 10,746 mg</p> <p>STiO2 + = z =STi = 2,5813.10-3 mTi= STi .10-3 48 = 132,902 .10-3 g = 132,902 mg</p> <p>Vy trong 100ml dung dch A ta c: mFe= 84,672 macr= 10,746 mTi= 132,902 = 423,4 mg = 53,73 mg = 619,51mg</p> <p>BI 3 : Cho 1g mu lom ( thnh phn H2SO4 , SO3 v SO2 ) vo nc pha thnh 250 ml .Chn 25 ml dung dch ht 21,2 ml NaOH 0,1 M ( chun n pH = 4) . Mc khc , cng chun 100 ml dung dch phn tch trn bng dung dch It ht 37 ml dung dch I2 0,025 N . Tnh thnh phn % cc cu t c trong mu ( Bit H2SO3 c pK1 =1,76 ; pK2 = 7,21 ). BI GII : lum ( H2SO4 ; SO3 ; SO2 ) vo nc pha thnh 250 ml ta c dung dch c cha H2SO4; H2SO3 do: SO3 +H2O SO2 +H2O Ta c : H2SO3 HSO3Nhn xt :11 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>H2SO4 H2SO3 H+ + HSO3H+ +SO32K1 = 10-1,76 K2 = 10-7,21</p> <p>CHNG III : CHUN OXI HA KH</p> <p>pH =</p> <p>= 4,49</p> <p>pH =4</p> <p>Chun n pH = 4 H2SO4 + 2NaOH Na2SO4 + 2H2O H2SO3 + NaOH NaHSO3 + H2O = SO3 = SO2 = Gi x l s gam H2SO4 , y l s gam SO3 , z l s gam SO2 Ta c: S lg H2SO4 + S lg SO3 + S lg SO2 = S lg NaOH</p> <p>Chun vi I2: SO2 + 2 H2 + I2 SO2 = S lg SO2 = S lg I2 H2SO4 + 2HI</p> <p> z = 0,148</p> <p>(2)</p> <p>x +y +z = 1 (3) Gii phng trnh (1) ,(2) ,(3) ta c x= 0,5254 ; y= 0,3266 ; z = 0,1480</p> <p>12 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Phn trm ca H2SO4 trong lum l :</p> <p>Phn trm ca SO3 trong lum l :</p> <p>Phn trm ca SO2 trong lum l : 100-52,54 -32,66 = 14,8 %</p> <p>BI 4: 1,234 g cht phn tch cha PbO v PbO2 c ch ha vi 20ml H2C2O4 0,25 M kh PbO2 thnh Pb2+ . Sau dung dch c trung ha bng NH3 kt ta ton b ch di dng xalat ch . Chun nc lc thu c bng dung dch KMnO4 0,04M th ht 10ml. Ho tan kt ta trong axit v chun dung dch bng dungdch KMnO4 0,04M ht30 ml.Hy tnh thnh phn % ca PbO v PbO2 trong mu phn tch bit PbO = 223 ; PbO2 = 239 .</p> <p>BI GII : Tm tt qu trnh phn tch mu:</p> <p>PbO, PbO2 H2C2O4 Pb2+,PbC2O4</p> <p>H2C2O4 H2C2O4d KMnO4Axit ho CO2, H2O KMnO4 CO2, H2O PbC2O4 H2C2O4</p> <p>13 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Gi s ng lng gam ca PbO v PbO2 ln lt l x v y Ch ho hn hp bng dung dch H2C2O4. Khi cho H2C2O4 vo th: *Mt phn H2C2O4 dng ho tan PbO, sau to kt ta PbC2O4 PbO + H2C2O4 PbC2O4 + H2O (1) Gi S1 l s ng lng gam ca H2C2O4 dng trong phn ng (1). Vy ta c: x = S1</p> <p>*Mt phn dng kh PbO2 thnh Pb2+: 2 H2C2O4 2H+ + C2O42Pb2+ +2 H2O</p> <p>PbO2 + 4H+ +2e C2O422CO2+2e</p> <p>PbO2 + 2H2C2O4</p> <p>Pb2++2CO2 +2 H2O + C2O42- (2)</p> <p>Gi S2 l s ng lng gam ca H2C2O4 dng trong phn ng (2). Vy ta c: y = S2 *Mt phn H2C2O4 dng to kt ta PbC2O4 vi Pb2+ phn ng (2) Pb2+ + C2O42PbC2O4 = y (3)</p> <p>Ta c S Pb2+ to ra phn ng (2) =</p> <p>Gi S3 l s ng lng gam ca H2C2O4 dng trong phn ng (3)</p> <p>14 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Ta c: y = S3 hay S2 = S 3</p> <p>*Phn H2C2O4 cn d l phn nc lc thu c, c chun bng dung dch KMnO 4 0,04M ht 10ml 5 H2C2O4 2H+ + C2O42Mn2+ + 4H2O</p> <p>+ 2 MnO4 + 8H + 5e</p> <p>5 C2O425H2C2O4 + 2MnO4- + 6H+</p> <p>2CO2+2e 2Mn2+ + 10CO2 + 8H2O (4)</p> <p>Gi S4 l ng lng gam ca H2C2O4 con d trong dung dch. Ta c: S4 = S KMnO4 = = 2.10-3</p> <p>*Phn kt ta PbC2O4 thu c l phn ng (1) v (3). Ho tan kt ta trong axit: PbC2O4+ H+ V vy : S H 2C2O4 (5) = S1 + S3 *Chun dung dch thu c bng dung dch KMnO4 0,04M ht 30 ml. Tc l chun lng H2C2O4 to thnh: 5H2C2O4 + 2MnO4- + 6H+ Ta c: Hay : S H 2C2O4 = S KMnO4 S1 + S3 = = 6.10-3 2Mn2+ + 10CO2 + 8H2O Pb2+ + H2C2O4 (5)</p> <p>*Mt khc : tng s ng lng gam ca H2C2O4l: S = S1 + S2 + S3 + S4 = = 0,01</p> <p>15 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Vy ta c: S1 + S2 + S3 + S4 = 0,01 S2 = S3 S4 = 2.10-3 S1 + S3 = 6.10-3 Vy : SPbO = S1 = 4.10-3 =x Khi lng ca PbO l : mPbO = SPbO 4.10-3 S1 = 4.10-3 =x S2 = 2.10-3 = y S3 = 2.10-3 S4 = 2.10-3</p> <p>223 = 0,446 (g) 2</p> <p>Phn trm ca PbO trong mu phn tch:</p> <p>S PbO2 = S2 = 2.10-3 = y Khi lng ca PbO2 l : mPbO2 = S PbO2 Phn trm ca PbO2 trong mu phn tch l : = 2.10-3</p> <p>239 = 0,239 (g) 2</p> <p>BI 5 : xc nh chun ca KOH v KMnO4 ngi ta dng kalittraxalat( KHC2O4.H2C2O4.2H2O ) lm cht u .Nng dung dch KOH xc nh c l 0,09963 N v ca KMnO4 l 0,1328 N . Bit rng trong c hai trng hp trong c hai trng hp th tch ca cc dung dch KOH v KMnO4 ly chun u bng 50ml .Hy tnh s gam oxalate16 tiu th trong phn ng trn Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>BI GII : *Xt trng hp chun ca KOH : 3 KOH + KHC2O4.H2C2O4.2H2O K2C2O4.K2C2O4.2H2O + 3 H2O ng lng ca KHC2O4.H2C2O4.2H2O l : = = 84,667 (1)</p> <p>Ta c : S lg KHC2O4.H2C2O4.2H2O (1) = S lg KOH = = =4,9815.10-3</p> <p>Khi lng ca KHC2O4.H2C2O4.2H2O tham gia khi chun KOH l : 4,9815.10-3 84,667 = 0,4218 (g) *Xt trng hp chun ca KMnO4 :</p> <p>5</p> <p>H2C2O4</p> <p>2H+ + C2O42Mn2+ + 4H2O 2CO2+2e 2Mn2+ + 10CO2 + 8H2O (2)</p> <p>+ 2 MnO4 + 8H + 5e</p> <p>5 C2O425H2C2O4 + 2MnO4- + 6H+ Ta c :</p> <p>S lg MnO4 = S lg H2C2O4 =</p> <p>=</p> <p>= 6,64.10-3</p> <p>S lg ca KHC2O4.H2C2O4.2H2O tham gia khi chun KMnO4 =S lg H2C2O4 =6,64.10-3</p> <p>ng lng ca KHC2O4.H2C2O4.2H2O l :</p> <p>=</p> <p>= 63,5</p> <p>Khi lng ca KHC2O4.H2C2O4.2H2O tham gia khi chun KMnO4 l : 6,64.10-3 63,5 = 0,4216 (g)17 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>Vy : Khi lng ca KHC2O4.H2C2O4.2H2O tiu th trong cc qu trnh chun trn l : 0,4218 + 0,4316 = 0,8434 (g)</p> <p>BI 6: Mt mu phn tch c cha MnO2 v tp cht tr . xc nh % MnO2 c trongmu , ngi ta ch ha 0,25 g mu phn tch vi 25 ml H2C2O4 0,25 N .Cho thm 5ml dung dch HNO3 1M kt ta hon ton , sau cho vo dung dch 1ml KI 10% v 0,5 ml h tinh bt .Chun hn hp trn bng K2Cr2O7 0,02 M th ht 10,75 ml dung dch chuyn t mu xanh nht sang mu xanh m . a) Hy gii thch ni dung th nghim trn bng phng trnh phn ng .b) Tnh % MnO2 trong mu phn tch .</p> <p>BI GII : a) Cc phn ng ln lt l:</p> <p>MnO2 + 2e +4H+ H2C2O4 C2O422H+ + C2O422CO2+2e</p> <p>Mn2+ + 2H2O</p> <p>18 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>H2C2O4 +MnO2 + 2H+ Mn2+ + 2CO2 +2H2O</p> <p>(1)</p> <p>H2C2O4 +MnO2 MnCO3 + 2CO2 +H2O</p> <p>(2)</p> <p>3 H2C2O4 3 C2O422</p> <p>2H+ + C2O422CO2+2e NO + 2H2O (3)</p> <p>HNO3 + 3H+ + 3e</p> <p>3H2C2O4 +2HNO3 6CO2 + 4H2O + 2NO</p> <p>6 Mn2+ + 4H2O2</p> <p>MnO4- + 8H+ + 5e 2Cr3+ + 7H2O</p> <p>5 Cr2 O7 + 14H+ + 6e</p> <p>5Cr2O72- +6Mn2+ + 22H+10Cr3+ + 6MnO4- + 11H2O</p> <p>(4)</p> <p>Cr2O7 + 14H+ + 6e3</p> <p>2</p> <p>2Cr3+ + 7H2O 2II2 + 2e (5)</p> <p>Cr2O72-+ 6I- + 14H+ 2Cr3+ + 3I2 + 7H2O</p> <p>T phng trnh ta c: mu xanh nht l mu ca ion Cr3+ , cn xanh m l do iot sinh ra (5) kt hp vi h tinh bt nn c mu xanh m . Nn ta thy hin tng dung dch chuyn t mu xanh nht sang mu xanh m</p> <p>19 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>b) Ta c : = =</p> <p>=</p> <p>= 6,25 10-3 = 1,29 10-3</p> <p>= 2,48 10-3</p> <p>Khi lng MnO2 trong mu phn tch l : 2,48 10-3 87 = 0,215 (g) Vy phn trm MnO2 trong mu phn tch l : % = = 86 %</p> <p>20 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>TRNG I HC S PHM HU KHOA HA HC </p> <p>Cn b hng dn Thy Nguyn Hu Hin</p> <p>Sinh vin Trn Th M L Lp: Ha 3B</p> <p>HU, 11 /2011</p> <p>21 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>TRNG I HC S PHM HU KHOA HA HC </p> <p>Cn b hng dn Thy Nguyn Hu Hin</p> <p>Sinh vin Trn Th M L Lp: Ha 3B</p> <p>HU, 11 /2011</p> <p>22 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>TRNG I HC S PHM HU KHOA HA HC </p> <p>HU, 11 /2011</p> <p>23 Trn Th M L Lp Ha 3B Bi tp ln</p> <p>CHNG III : CHUN OXI HA KH</p> <p>24 Trn Th M L Lp Ha 3B Bi tp ln</p>