Bản Tường Trình Số 11

AI HOC HUTRNG AI HOC KHOA HOC KHOA HOA HOC

H v tn sv:Mai Quang Hong BN TNG TRNH HA HCBn tng trnh s 3: THIC - CHTh su, ngy 25, thng 04, nm 2014

1.TN TH NGHIM2. HIN TNG QUAN ST, GII THCH V PHNG TRNH HA HC

Th nghim 1:Tnh cht ca Thic(II) CloruaCch tin hnh:Ti liu: bi ging thc tp ha v c trang 85-2.1.2

Khi ta cho nc vo tinh th thic(II) clorua th tinh th tan ra , to kt ta mu trng, Gii thch: Khi ha tan tinh th SnCl2 vo nc th thu c dung dch mui thic(II) clorua. Mui ny tan tt trong nc v b thy phn mnh to thnh mui baz Sn(OH)ClSnCl2 + H2O Sn(OH)Cl + HCl

Khi thm t t dd NaOH n d vo ng nghim cha dd SnCl2 th lc u xut hin kt ta trng, kt ta tng dn khi thm t t dd NaOH, sau kt ta tan khi lng NaOH d.Gii thch: lc u xy ra phn ng gia mui SnCl2 v baz NaOH to thnh mui mi NaCl v baz mi Sn(OH)2 (kt ta trng). nhng Sn(OH)2 l mt hydroxit lng tnh nn tip tc phn ng vi lng d NaOH to phc Na2[Sn(OH)4] v tan ra.SnCl2 + 2NaOH 2NaCl + Sn(OH)2Sn(OH)2 + NaOH Na2[Sn(OH)4]Kt ta to thnh mt phn do SnCl2 thy phn SnCl2 + H2O Sn(OH)Cl + HClKhi thm NaOH vo th s trung ha HCl lm cn bng dch chuyn theo chiu thun, chiu to Sn(OH)Cl nn kt ta tng. HCl + NaOH NaCl + H2ONhng khi lng NaOH d s ha tan Sn(OH)Cl to phc Na2[Sn(OH)4]Sn(OH)Cl + NaOH

Khi thm dd HCl m c vo ng nghim cha dd SnCl2. Khi pha long dd bng nc th thy xut hin kt ta trng trong.Gii thch: Khi thm HCl m c vo th xy ra phn ng to phc gia SnCl2 v HCl, to thnh phc tan H2[SnCl4] axit tetracloro thic(II)SnCl2 + 2HCl H2[SnCl4]Khi pha long dd trn th xut hin kt ta trng trong do xy ra s hydrat ha phc H2[SnCl4] to thnh kt ta thic(II) Clorua dihydrat SnCl2.2H2OH2[SnCl4] + 2H2O SnCl2.2H2O +2HClMt khc: Khi pha long dd th mt lng dd SnCl2 b thy phn to kt ta Sn(OH)ClSnCl2 + H2O Sn(OH)Cl +HClKhi pha long th kt ta tch ra di dng kt ta trng trong, do khi pha long dd th qu trnh hydrat ha din ra mnh hn qu trnh ha tan bng axit.

Th nghim 2:Tnh cht ca dung dch SnCl2Cch tin hnh:Ti liu: bi ging thc tp ha v c trang 85-2.1.2.4

Khi cho dd SnCl2 tc dng vi dd Hg2(NO3)2 th thu c kt ta mu xm, ta nhit.Gii thch: tt c cc mui ca Sn(II) l nhng cht kh rt mnh, cn Hg2(NO3)2 l cht oxi ha mnh nn Sn2+ trong SnCl2 kh Hg22+ v Hg0Sn2+ - 2e Sn4+ 0 =0,15VHg22+ + 2e 2Hg 0 = 0,788VTa c 0(Sn2+/Sn4+) < 0 (Hg22+/2Hg) nn phn ng xy ra theo chiu:SnCl2 + Hg2(NO3)2 2Hg + Sn(NO3)2Cl2Sau Hg b oxi ha trong oxi khng kh to oxit thy ngn mu xm.2Hg + O2 2HgO

Khi cho SnCl2 tc dng vi dd Br2 trong mi trng axit HCl th ta thy dd Br2 mt mu.Gii thch: do SnCl2 l cht kh mnh 0 (Sn2+/Sn4+)=0,15, trong khi Br2 l cht oxi ha rt mnh 0 (Br2/2Br-)=1,070V nn xy ra phn ng SnCl2 + Br2 SnCl2Br2HCl trong th nghim ch ng vai tr l mi trng, ngn cho SnCl2 khng b thy phn.T hai th nghim trn ta thy SnCl2 th hin tnh kh rt mnh: Sn2+-2e Sn4+


Th nghim 3:iu ch SnCl2 v SnCl4Cch tin hnh:Ti liu: bi ging thc tp ha v c trang 85-2.1.2.4

iu ch SnCl2 t Sn: ta cho kim loi Sn tc dng vi dung dch HCl c, nng(phn ng xy ra nhanh hn)Sn + 2HCl.n SnCl2 + H2iu ch SnCl4 t Sn: ta cho kim loi Sn tc dng vi kh Cl2Sn + Cl2 SnCl4Do kh Cl2 c tnh oxi ha rt mnh, mnh hn nhiu so vi HCl, 0 (Cl2/2Cl-) =1,359 > 0(2H-/H2)=0, nn Sn b Cl oxi ha ln Sn+4 trong khi Sn ch b HCl oxi ha ln Sn+2 ( tnh cht ny ging Fe kim loi)

Nhit nng chy ca SnCl2 = 2470c ln hn rt nhiu so vi SnCl4 = -33,3 0cDo lin kt trong SnCl2 l lin kt ion nn khi ph hy cu trc tinh th ca SnCl2 cn mt nng lng ln nn nhit nng chy caoCn lin kt trong SnCl4 l lin kt cng ha tr nn ch cn mt nng lng thp c th ph v cu trc ca n, nn c nhit nng chy thp.

Th nghim 4:Thic (II) sunfuaCch tin hnh:Ti liu: bi ging thc tp ha v c trang 85-2.2.1

Th nghim ny khng tin hnh: Theo l thuyt th khi ta cho dng kh H2S li qua dd SnCl2, un nng th thu c kt ta mu nu, khng tan. Do xy ra phn ng trao i gia dd H2S v dd SnCl2 to kt ta SnS. H2S + SnCl2 SnS +2HClTSnS = 3,2.10-38KH2S = 10-21 kcb = = 3,2.10-2 (Pb2+/Pb nn phn ng xy ra theo chiu3Pb + 8HNO3 3Pb(NO3)2 + 2NO + 4H2O2NO + O2 2NO2Khi tc dng vi dd HNO3 c, nng th Pb kh NO3- v N+4 gii phng kh NO2 khng muPb + HNO3 Pb(NO3)2 + 2NO2 + 2H2O

Pb khng tc dng vi HCl long v H2SO4 long v PbCl2 v PbSO4 rt bn khng tan trong nc ngn cho Pb tip xc vi axit nn trong trng hp ny Pb ch c tng tc b mt.Khi tc dng vi dd axit HCl m c v H2SO4 m c, th tc nhn oxi ha rt mnh H+ v SO42- th Pb tan ra, kh thot ra nhiu, ta nhit mnh.Gii Thch: lc u ch tc dng vi HCl v H2SO4 to lp mui bn, khng tan PbCl2 v PbSO4. Nhng do nng axit qu m c nn cc mui ny nhanh chng to phc tan vi axit HCl v mui tan hidro sunfat vi H2SO4.Pb + 2HCld PbCl2 + H2PbCl2 + 2HCld H2[PbCl4]

Pb + 2H2SO4 d PbSO4 + SO2 + 2H2OPbSO4 + H2SO4 Pb(HSO4)2

Khi tc dng vi dd NaOH long th Pb khng phn ng, nhng Pb li phn ng vi dd NaOH c, un nng, to phc Na2[Pb(OH)4] v gii phng kh H2Gii thch: iu kin bnh thng ch c ph bi mt lp oxit PbO2 bn, ngn cho Pb khng tc dng vi cc tc nhn khc, nn Pb khng tc dng vi NaOH long, Nhng khi cho NaOH c th u tin lp oxit b ph v. Pb(OH)2 c tnh lng tnh nn sau Pb tan trong NaOH to phc tan.Pb + 2NaOHd +2H2O Na2[Pb(OH)4] + H2


Th nghim 7 :Tnh cht ca PbO2Cch tin hnh:Ti liu thc tp ha v c trang 86-3.2.2

PbO2 l mt oxit bn nn n khng phn ng vi HCl v H2SO4 long.PbO2 khng tc dng vi HNO3 c v long: v PbO2 l cht c tnh oxi ha, m HNO3 cng th hin tnh oxi ha mnh, nn c 2 cht ch c xu hng gim s oxi ha ca NO3- v Pb+4, m s oxi ha ca NO3- v Pb+4 u mc cao nht, khng th gim na.

Khi tc dng vi HCl m c : dd c mu vng nht,c kt ta trng, c kh mi xc bay raGii thch: PbO2 c tnh oxi ha mnh, trong mi trng HCl m c Pb4+ b oxi ha v Pb2+ to lt ta PbCl2, gii phng kh Cl2 mi xc, kh Cl2 mt phn tan trong dd to thnh nc Cl2 mu vng nht.PbO2 + 4H+ + 2e Pb2+ + 2H2O 0 = 1,468V2Cl- - 2e Cl2 0 = 1,360PbO2 + 4HCld PbCl2 + Cl2 +2H2OCl2 + H2O HCl + HClO

Khi tc dng vi dd H2SO4 th c kt ta mu trng, dd c mu xanh nuGii thch: trong mi trng H2SO4 m c PbO2 va c tnh t oxi ha-kh Pb4+ + 2e Pb2+2O2- + 4e O2Nn phn ng Pb4+ oxi ha v Pb2+ dng kt ta PbSO4 mu trng.PbO2 + 2H2SO4 dd PbSO4 + O2 + H2O

Khi tc dng vi H2O2 th ta thy PbO2 tan ra, si bt kh , ta nhitTa c 0 (PbO2/Pb2+) = 1,468 > 0 (O2/H2O2)=0,7 nn phnr ng xy ra theo chiuPbO2 + H2O2 + 2H+ Pb2+ + O2 + 2H2O

Khi cho PbO2 tc dng vi MnSO4 trong mi trng H2SO4 th Mn+2 kh ln Mn+7nn ta thy dd c mu hng5PbO2 + MnSO4 + 3H2SO4 2KMnO4 + 3PbSO4 + 2H2O

PbO2 khng phn ng vi Cr2(SO4)3 trong mi trng KOHNhng theo l thuyt th phn ng trn c th xy ra. Do 0(PbO2/Pb2+)= 1,46V > 0(CrO4-=4H2O/Cr3+ +8OH-)=-0,13V2PbO2 + Cr2(SO4)3 +4KOH 2K2CrO4 + 3PbSO4 + 2H2O

Tc dng vi KIPbO2 + 2KI + 2H2O Pb(OH)3 +I2 + 2KOH

PbO2 tan c trong kim c to ra phc [Pb(OH)6]2-PbO2 + 2NaOH + 2H2O Na2[Pb(OH)6]Trong cc th nghim trn ta thy PbO2 l cht oxi ha mnh.


Th nghim 8:Tnh cht ca Pb(OH)2Cch tin hnh:Ti liu thc tp ha v c trang 87-3.3.2

Kt ta Pb(OH)2 tan trong dung dch HNO3 to thnh dd trong sut, do xy ra phn ng gia bazo v axitPb(OH)2 + 2HNO3 Pb(NO3)2 + 2H2ODo Pb(OH)2 l mt hydroxit lng tnh nn n cng tan c trong dd NaOH to thnh phc Na2[Pb(OH)4]Pb(OH)2 + 2NaOH Na2[Pb(OH)4]

Trong dung dch c pH < 7 ch tn ti dng Pb2+Trong dung dch c pH > 7 ch tn ti dng phc [Pb(OH)4]2-

Mun ha tan kt ta ta dng axit HNO3 m khng dng axit HCl hoc H2SO4 v khi dng HNO3 th to mui tan HNO3Cn nu dng HCl hoc H2SO4 th to mui khng tan PbCl2 v PbSO4 ngn khng cho Pb(OH)2 tip tc phn ng vi axit.C th thay th HNO3 bng axit CH3COOH


Th nghim 9:PbCl2Cch tin hnh:Ti liu thc tp ha v c trang 87-3.4.1

Khi thm dd NaCl bo ha vo dd Pb(CH3COO)2 th xut hin kt ta trng lng xung dng tinh th, khng tan do xy ra phn ng trao i gia mui NaCl v mui Pb(CH3COO)2 to thnh kt ta PbCl22NaCl + Pb(CH3COO)2 2CH3COONa + PbCl2

Khi thm dd HCl m c vo dd PbCl2 th thu c dd trong sut. khi pha long bng nc th xut hin kt ta trng.PbCl2 phn ng vi HCl m c to phc H2[PbCl4]. Khi pha long th phc ny b thy phn to li kt ta PbCl2PbCl2 + 2HCl H2[PbCl4]

Tng hp PbCl2 phi dng dung dch bo ha v PbCl2 l mui thy phn mnh trong cc dd long to kt ta Pb(OH)2. V vy dng dd bo ha ngn s thy phn .


Th nghim 10:PbI2Cch tin hnh:Ti liu thc tp ha v c trang 87-3.4.2

Khi cho dd KI vo dd Pb(CH3COO)2 th thu c kt ta mu vng m c PbI2Do xy ra phn ng trao i gia 2 dd mui Pb(CH3COO)2 + 2KI PbI2 + 2CH3COOK

Khi ha tan PbI2 trong nc th kt ta khng tan , nhng khi dun nng th kt ta tan, dd t mu vng chuyn sang mu trong sut. ngui th c kt ta tr li .do tan ca PbI2 ph thuc vo nhit .

Khi cho dd KI vo tinh th PbI2 th kt ta tan ra. Do PbI2 to phc tan vi I-PbI2+ 2KI K2[PbI4]

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Bản Tường Trình Số 11