Giao Trinh Ly Thuye Thuc Hanh Hoa Phan Tich

8/8/2019 Giao Trinh Ly Thuye Thuc Hanh Hoa Phan Tich

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B Y t

ha phn tchl thuyt v thc hnhSch o to Trung hc Dc

Ch bin:

PGS.TSKH. L Thnh Phc - CN. Trn Tch

M s: T.60.Y.3

Nh xut bn Y hcH Ni - 2007


3/312

Ch o bin son:

V Khoa hc v o to, B Y t

Ch bin:

PGS. TSKH. L Thnh Phc

CN. Trn Tch

Bin son:

PGS. TSKH L Thnh PhcCN. Trn Tch

ThS. Nguyn Nh H

TS. Nguyn Th Kiu Anh

Tham gia t chc bn tho:

TS. Nguyn Mnh Pha

ThS. Ph Vn Thm

Bn quyn thuc B Y t (V Khoa hc v o to)

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li gii thiu

Thc hin mt s iu ca Lut Gio dc, B Y t ban hnhchng trnh khung v chng trnh gio dc ngh nghip cho vic o to

trung cp ngnh Y t. B Y t t chc bin son ti liu dy hc cc mnc s v chuyn mn theo chng trnh trn nhm tng bc xy dng bsch chun trong cng tc o to nhn lc y t.

SchHa phn tch (L thuyt v thc hnh) c bin son da trnchng trnh gio dc ngh nghip ca B Y t bin son trn c s chngtrnh khung c ph duyt. Sch c cc nh gio lu nm v tmhuyt vi cng tc o to bin son theo phng chm: Kin thc c bn,h thng; ni dung chnh xc, khoa hc; cp nht cc tin b khoa hc, kthut hin i v thc tin Vit Nam. Sch c cu trc gm 4 phn bm

st chng trnh gio dc vi nhng ni dung c bn nht v phn tchnh tnh v nh lng gip hc sinh sau khi hc c c nhng kin thcc bn, k nng thc hnh phn tch nh tnh v nh lng p dngtrong thc t pha ch cc dung dch chun, thc hin cc php chun th tch, nh lng theo phng php khi lng thng gp v tnh ckt qu ca php phn tch. ng thi qua rn luyn c tc phonglm vic khoa hc, thn trng, chnh xc, trung thc trong hot ng nghnghip khi ra trng. Sch l tin cc gio vin v hc sinh cctrng c th p dng phng php dy hc tch cc.

Sch Ha phn tch (L thuyt v thc hnh) c Hi ngchuyn mn thm nh sch v ti liu dy - hc ca B Y t thm nhvo nm 2006. B Y t ban hnh lm ti liu dy - hc chnh thc cangnh Y t. Trong thi gian t 3 n 5 nm, sch phi c chnh l, bsung v cp nht.

B Y t xin chn thnh cm n PGS.TSKH. L Thnh Phc, CN. TrnTch, ThS. Nguyn Nh H v TS. Nguyn Th Kiu Anh ca Trng i hcDc H Ni dnh nhiu cng sc hon thnh cun sch ny, cm nPGS.TS. Trn T An v ng Nguyn Vn Th c, phn bin cunsch c hon chnh kp thi phc v cho cng tc o to nhn lc Y t.

V ln u xut bn nn cn khim khuyt, chng ti mong nhn c kin ng gp ca ng nghip, cc bn sinh vin v cc c gi lnxut bn ln sau sch c hon thin hn.

V khoa hc v o to

B y t

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Mc lc

Li gii thiu 3

Phn I. L thuyt phn tch nh tnh 15

Bi1:Mt s nh lut v khi nim c bn trong Ha phn tch 17

1. Cc nh lut 17

1.1. nh lut bo ton khi lng 17

1.2. nh lut thnh phn khng i 18

1.3. nh lut ng lng 18

2. Nhng khi nim c bn 22

2.1. Nng dung dch. Cc cch biu th nng 22

2.2. S in ly ca nc. Thang pH 25

2.3. iu kin kt ta v ha tan. Tch s tan 28

2.4. Phn ng oxy ha kh 30

2.5. Phc cht

Bi tp (Bi 1)

33

35

Bi2: i cng v Phn tch nh tnh cc ion trong dung dch 40

1. Cc phng php phn tch nh tnh 40

1.1. Phng php ha hc 40

1.2. Phng php vt l - ha l 40

1.3. Phn tch t v phn tch kh 41

1.4. Phn tch ring bit v phn tch h thng 41

2. Cc phn ng dng trong phn tch nh tnh 422.1. Cc loi phn ng 42

2.2. nhy v tnh c hiu ca phn ng 43

2.3. Thuc th trong cc phn ng nh tnh 44

3. Phn tch nh tnh cation theo phng php acid-base 44

4. Phn tch nh tnh anion 47

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5. Nhng k thut c bn trong thc hnh ha phn tch nh tnh 48

5.1. Ra dng c 48

5.2. Cch un nng 49

5.3. Lc 50

5.4. Ly tm 51

5.5. Ra kt ta 51

5.6. Thc hin phn ng

Bi tp (Bi 2)

52

54

Bi3: Cation nhm I: Ag+, Pb2+, Hg22+ 561. Tnh cht chung 56

2. Cc phn ng phn tch c trng ca cc cation nhm I 56

3. S phn tch

Bi tp (Bi 3)

61

61

Bi4: Cation nhm II: Ca2+, Ba2+ 631. Tnh cht chung 63

2. Cc phn ng phn tch c trng ca cation nhm II 63

3. S phn tchBi tp (Bi 4)

6565(69)

Bi5: Cation nhm III: Al3+, Zn2+ 661. Tnh cht chung 66

2. Cc phn ng phn tch c trng ca cation nhm III 66

3. S phn tch

Bi tp (Bi 5)

69

70

Bi6: Cation nhm IV: Fe3+, Fe2+, Bi3+, Mg2+, Mn2+ 711. Tnh cht chung 71

2. Cc phn ng phn tch c trng ca cation nhm IV 71

3. S phn tch

Bi tp (Bi 6)

75

75

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Bi7: Cation nhm V: Cu2+, Hg2+ 771. Tnh cht chung 77

2. Cc phn ng phn tch c trng ca cation nhm V 77

3. S phn tch

Bi tp (Bi 7)

79 (82)

79Bi8: Cation nhm VI: Cu2+, Hg2+ 801. Tnh cht chung 80

2. Cc phn ng phn tch c trng ca cation nhm VI 80

3. S phn tch

Bi tp (Bi 8)

82

82

Bi9: Anion nhm I: Cl-, Br-, I-, SCN-, S2O32- 831. Tnh cht chung 832. Cc phn ng phn tch c trng ca anion nhm I 83

3. S phn tch

Bi tp (Bi 9)

86

87

Bi10: Anion nhm II: CO32-, PO43-, CH3COO-, AsO33-, AsO43-, SO32-SO42-, (S2O32-)

88

1. ng li phn tch nhm II 88

2. Cc phn ng c trng ca anion nhm II 883. S phn tch

Bi tp (Bi 10)

92

93

Bi11: Phn tch hn hp cation v anion trong dung dch 941. Nhn xt v th s b 94

1.1. Nhn xt nh gic quan 94

1.2. Th pH ca dung dch 95

1.3. Th tnh bay hi ca cht tan 961.4. Th mu ngn la 96

1.5. Th mt s phn ng 96

2. Phn tch anion 97

3. Phn tch cation 97

4. Nhn xt kt qu 98

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Phn II. Thc hnh phn tch nh tnh 99

Ni quy phng th nghim ha phn tch nh tnh 101

Quy tc an ton phng th nghim 102

Vi quy nh v s dng ha cht 104Bi1:Dng c v k thut thc nghim c bn trong Ha phn tch

nh tnh105

Bi 2:nh tnh cation nhm I: Ag+, Pb2+, Hg22+ 108

Bi3: nh tnh cation nhm II: Ba2+, Ca2+ v nhm III: Ae3+, Zn2+ 110Bi4: nh tnh cation nhm IV: Fe2+, Fe3+, Bi3+, Mg2+, Mn2+ 113Bi5: nh tnh cation nhm V: Cu2+, Hg2+ v nhm VI: Na+, K+, NH4+ 115Bi6: Phn tch tng hp cc nhm cation theo phng php acid - base 118Bi7: nh tnh anion nhm I: Cl-, Br-, I-, SCN-, S2O32- 120Bi8: nh tnh anion nhm II: CO32-, CH3COO-, PO43-, AsO33-, AsO43-,

SO32-, SO42-, (S2O32-)123

Bi9: Phn tch hn hp cation v anion trong dung dch 127Phn III. L thuyt phn tch nh lng

129

Bi 1. i cng v ha phn tch nh lng 131

1. i tng ca phn tch nh lng 131

2. Phn loi cc phng php phn tch nh lng 131

2.1. Cc phng php ha hc 131

2.2. Cc phng php vt l v ha l 132

3. Nguyn tc chung ca cc phng php ha hc dng trongnh lng

133

4. Sai s trong phn tch nh lng ha hc 134

4.1. Mt s khi nim 134

4.2. Cc loi sai s 134

4.3. Cch ghi d liu thc nghim theo qui tc v ch s c ngha 136

Bi tp (Bi 1) 136

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Bi 2. Phng php phn tch khi lng 137

1. Ni dung v phn loi 137

1.1. Phng php kt ta 137

1.2 Ph

ng php bay hi 1382. Nhng ng tc c bn ca phng php phn tch khi lng 139

2.1. Ha tan 139

2.2. Kt ta 139

2.3. Lc ta 140

2.4. Ra ta 140

2.5. Sy v nung 141

2.6. Cn 1413. Cch tnh kt qa trong phn tch khi lng 141

3.1. Trong phng php kt ta 141

3.2. Trong phng php bay hi 143

4. Cn phn tch 143

4.1. Cn c hc 143

4.2. Cn in t 143

5. Mt vi th d p dng nh lng bng phng php khi lng 1445.1. nh lng Clorid 144

5.2. nh lng Na2SO4 145

Bi tp (Bi 2) 146

Bi 3. Phng php nh lng th tch 147

1. Ni dung ca phng php phn tch th tch 147

2. Yu cu i vi mt phn ng dng trong phn tch th tch 148

3. Phn loi cc phng php th tch 148

3.1. Phng php acid-base 148

3.2. Phng php oxy ha kh 148

3.3. Phng php kt ta 149

3.4. Phng php to phc 149

4. Cc k thut chun 149

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4.1. nh lng trc tip 149

4.2. nh lng ngc 149

4.3. nh lng th 149

5. Cch s dng mt s dng c dng trong phng php th tch 150

5.1. S dng buret 150

5.2. S dng pipet 151

5.3. S dng bnh nh mc 152

6. Hiu chnh dung tch cc dng c ong o th tch chnh xc 153

6.1. Nguyn tc 153

6.2. Hiu chnh dung tch bnh nh mc 153

6.3. Hiu chnh dung tch ca pipet 155

6.4. Hiu chnh dung tch ca buret 155

7. Cch tnh kt qu trong phng php th tch 156

7.1. Quy tc chung 156

7.2. Tnh kt qu theo nng ng lng thuc th 156

7.3. Tnh kt qu theo chun ca thuc th 157

7.4. Mt s th d 158

Bi tp (Bi 3) 159

Bi 4. Pha cc dung dch chun 161

1. Khi nim v dung dch chun 161

2. Cc cch pha dung dch chun 161

2.1. Pha ch t cht chun gc 161

2.2. Pha ch t cht khng phi l cht gc 163

2.3. Pha t ng chun 164

2.4. Cch iu chnh nng dung dch 1643. Pha mt s dung dch chun 165

3.1. Pha dung dch chun HCl 0,1N t HCl c 165

3.2. Pha dung dch chun KMnO4 0,1N 166

3.3. Pha dung dch chun I2 0,1N t I2 tinh khit thng hoa 167

3.4. Pha dung dch complexon III 0,1M t complexon II tinh khit 167

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3.5. Pha dung dch chun Na2S2O3 0,1N t Na2S2O3.5H2O 168

Bi tp (Bi 4) 169

Bi 5. nh lng bng phng php acid - base 170

1. Mt s khi nim c bn 1701.1. nh ngha acid, base theo Bronsted 170

1.2. Nc v pH 171

1.3. Cng ca acid v base 171

1.4. a acid, a base 171

1.5. Cng thc tnh [H+] v pH ca mt s dung dch 172

2. nh lng bng phng php acid-base 174

2.1. Nguyn tc 1742.2. Cht ch th trong phng php acid-base 175

2.3. Mt s trng hp nh lng acid-base 178

2.4. Mt s ng dng nh lng bng phng php acid-base 182

Bi tp (Bi 5) 186

Bi 6. nh lng bng phng php kt ta - nh lng bng phngphp to phc

188

1. Chun kt ta 1881.1. Mt s khi nim c bn 188

1.2. Phng php chun kt ta 190

2. Chun to phc 196

2.1. Mt s khi nim c bn 196

2.2. nh lng bng phng php to phc 198

Bi tp (Bi 6) 208

Bi 7. nh lng bng phng php oxy ha kh 210

1. Mt s khi nim c bn 210

1.1. nh ngha 210

1.2. Cng ca cht oxy ha v cht kh 210

1.3. Cn bng phng trnh phn ng oxy ha kh 211

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2. nh lng bng phng php oxy ha kh 212

2.1. Nguyn tc 212

2.2. Cht ch th trong phng php nh lng oxy ha kh 213

2.3. Phn loi cc phng php oxy ha kh 214

2.4. Mt s ng dng nh lng 217

Bi tp (Bi 7) 221

Phn IV. Thc hnh phn tch nh lng 223

Bi 1. Cn phn tch

Bi tp (Bi 1)

225

228

Bi 2. Xc nh m ca natri clorid v nh l

ng natri sulfatBi tp (Bi 2)

229233

Bi 3. Thc hnh s dng cc dng c phn tch nh lng - nhlng acid acetic

Bi tp (Bi 3)

234

239

Bi 4. Pha v xc nh nng dung dch acid hydrochloric 0,1 N

Bi tp (Bi 4)

240

244

Bi 5. Pha v xc nh nng dung dch natri hydroxyd 0,1 N

Bi tp (Bi 5)

245

248Bi 6. nh lng natri hydrocarbonat

Bi tp (Bi 6)

250

252

Bi 7. nh lng natri clorid bng phng php Mohr

Bi tp (Bi 7)

253

256

Bi 8. nh lng natri clorid bng phng php Fonhard

Bi tp (Bi 8)

257

260

Bi 9. Pha v xc nh nng dung dch kali permanganat 0,1 N

Bi tp (Bi 9)

261264

Bi 10. nh lng dung dch nc oxy gi 3%

Bi tp (Bi 10)

265

268

Bi 11. Pha v xc nh nng dung dch natri thiosulfat 0,1 N

Bi tp (Bi 11)

269

272

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Bi 12. nh lng dung dch glucose 5 %

Bi tp (Bi 12)

273

276

Bi 13. Pha v xc nh nng dung dch EDTA 0,05 M

Bi tp (Bi 13)

277

280

Phn ph lc 281

Ph lc 1. Dng c thng thng bng s, thy tinh v mt s mythng dng dng trong Ha phn tch

281

Ph lc 2. Danh php cht v c theo Dc in Vit Nam 289

Ph lc 3. Bng nguyn t lng cc nguyn t 298Ph lc 4. Hng s in ly ca cc acid v base 301

Ph lc 5. Th oxy ha kh chun (Eo) 302

Ph lc 6. Tch s tan ca mt s cht t tan 305

Ph lc 7. Hng s to phc 307

Gii p bi tp

Phn I. L thuyt phn tch nh tnh

Phn III. L thuyt phn tch nh lng

Phn IV. Thc hnh phn tch nh lng

309

309

312

313Ti liu tham kho 314

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Phn 1

L thuyt phn tch nh tnh

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Bi 1

Mt s nh lut v khi nim c bn

trong ha phn tch

Mc tiu

1. Gii thch c ni dung v ngha ca ba nh lut: nh lut bo ton khilng, nh lut thnh phn khng i v nh lut ng lng.

2. Trnh by c cc nh ngha v ba loi nng dung dch: nng phntrm, nng mol/L, nng ng lng v cch vn dng gii cc biton chuyn i gia cc loi nng y.

3. Trnh by c khi nim pH v s hnh thnh thang pH; khi nim ch thmu v cch xc nh pH bng ch th mu.

4. Nu c iu kin kt ta-ha tan mt cht da trn khi nim tch s tan5. Ch ra v c tn c cc thnh phn ca phc cht. Gii thch c ngha

ca hng s khng bn hoc hng s to phc nc v tng cng.

1. Cc nh lut

1.1. nh lut bo ton khi lng

Khi lng tng cng ca cc cht khng i trong mt phn ng ha hc.

S lng cc cht v tnh cht ca chng c th thay i, nhng khilng ca cc cht th gi nguyn khng i trc v sau phn ng. Ngayc nhng bin i sinh hc phc tp trong c th c lin quan n nhiuphn ng th khi lng vn c bo ton:

C6H12O6 + 6O2 6CO2 + 6H2O180g glucose + 192g kh oxy 264g carbon dioxyd + 108g nc

(372g nguyn liu trc phn ng 372g cht sau bin i)

* Nh nh lut bo ton khi lng m chng ta c th cn bng ccphng trnh ha hc v tnh c khi lng ca cc cht tham gia phnng v cc cht sn phm theo tng quan t l thun khi da vo phngtrnh phn ng cn bng.

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1.2. nh lut thnh phn khng i

Mt hp cht d c iu ch bng cch no th vn bao gm cng mtloi cc nguyn t v cng t s khi lng ca cc nguyn t trong hp cht.

c kt qu sau y thu c v thnh phn khi lng ca cc nguynt trong 20,0 g calci carbonat:

Phn tch theo khi lng S phn khi lng Phn trm khi lng

8,0g calci 0,40 calci 40%

2,4g carbon 0,12 carbon 12%

9,6g oxy 0,48 oxy 48%

20,0 g 1,00 phn khi lng 100% khi lng

nh lut thnh phn khng i cho ta bit rng, calci carbonat tinhkhit thu c t hoa cng mt ngn ni, t san h ngm di bin,hoc t bt k mt ngun no khc, th vn tm thy cng cc loi nguynt to thnh (calci, carbon, oxy) v cng mt s phn trm nh cho bit bng trn.

Nh vy, nh nh lut thnh phn khng i m mi hp cht xcnh c biu th bng mt cng thc ha hc nht nh.

C th suy ra khi lng nguyn t t t l khi lng ca n tronghp cht:

Khi lng nguyn t = Khi lng hp cht S phn khi lng nguyn t1 phn khi lng hp cht

Chng ta c th biu din phn khi lng theo bt k n v o khilng no nu tin dng cho tnh ton.

Cng cn ch l thnh phn khng i ch hon ton ng chonhng hp cht c khi lng phn t nh trng thi kh v lng. i vicht rn hoc polymer, do nhng khuyt tt trong mng tinh th hoctrong chui di phn t, thnh phn ca hp cht thng khng ng ngvi mt cng thc ha hc xc nh. V d, t l oxy/titan trong titan oxydiu ch bng cc phng php khc nhau dao ng t 0,58 n 1,33; cngthc ca st sulfid c th vit Fe1-xS vi x dao ng t 0 n 0,005; phn t

glycogen trong cc t bo gan v c c th gm 1000 n 500000 n vglucose; v.v...

1.3. nh lut ng lng

T nh lut thnh phn khng i ta thy rng cc nguyn t kthp vi nhau theo cc t l v lng xc nh nghim ngt. Do , ngi taa vo ha hc khi nim ng lng, tng t nh khi nim khilng nguyn t v khi lng phn t.

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1.3.1. nh ngha

Thc nghim ha hc xc nh rng: 1,008 khi lng hydro tc dngva vi:

8,0 khi lng oxy to thnh nc (H2O)

35,5 - clor - hydro clorid (HCl)23,0 - natri - natri hydrid (NaH)

16,0 - lu hunh - hydro sulfid (H2S)

3,0 - carbon - metHan (CH4)

v.v...

S phn khi lng m cc nguyn t tc dng va vi 1,008 phnkhi lng hydro li tc dng va vi nhau to thnh cc hp chtkhc. V d:

8,0 khi lng oxy + 3,0 khi lng carbon carbon dioxyd (CO2)35,5 khi lng clor + 23,0 khi lng natri natri clorid (NaCl)

16,0 khi lng lu hunh + 3,0 khi lng carbon carbon disulfid (CS2)

v.v...

Ngi ta gi s phn khi lng m cc nguyn t tc dng va vi1,008 phn khi lng hydro (v li tc dng va vi nhau) l nglng ca cc nguyn t, k hiu l E (equivalence), v vit: EH = 1,008; EO= 8; ECl = 35,5; ES = 16; v.v.. ch rng, ng lng l s phn khi lng

t

ng

ng gia cc cht trong phn ng nn c th s dng bt k n vkhi lng no biu th n (mg, g, kg...).

Do chnh t khi nim ng lng nu trn m vic xc nh nglng ca mt nguyn t hay ca mt hp cht khng nht thit phi xutpht t hp cht ca chng vi hydro. V d, tm ng lng ca km(Zn) khng th xut pht t phn ng ca km vi hydro, v iu kinthng phn ng ny khng xy ra. Tuy nhin, thc nghim d dng chothy: 32,5 khi lng km tc dng va vi 8 khi lng oxy (1E0) tothnh km oxyd (ZnO), vy, EZn = 32,5. Hoc tm ng lng H2SO4khng th bng cch cho acid ny tc dng vi hydro hoc oxy, nhng thc

nghim cho bit: 49 khi lng H2SO4 tc dng va vi 32,5 khi lngkm (1EZn), vy = 49. T y, c th a ra nh ngha chung cho

ng lng:42SOH

E

ng lng ca mt nguyn t hay hp cht l s phn khi lngca nguyn t hay hp cht kt hp hoc thay th va vi 1,008 phn

khi lng hydro hoc 8 phn khi lng oxy hoc vi mt ng lng cabt k cht no khc bit.

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Trong thc t ngi ta thng dng ng lng gam, vi quy c:

ng lng gam ca mt cht l lng cht c tnh bng gamv c tr s bng ng lng ca n.

Nh vy, EH = 1,008 g ; EO = 8 g ; ENa = 23 g

EZn = 32,5 g ; = 49 g42SOHE

1.3.2. nh lut ng lng ca Dalton

Cc cht tc dng vi nhau theo cc khi lng t l vi ng lngca chng.

Ni cch khc: S ng lng ca cc cht trong phn ng phi bngnhau.

nh lut c th hin qua h thc n gin:

B

A

m

m

= BA

E

E

hoc AA

E

m

= BB

E

m

y: mA, mB l khi lng tnh bng gam ca cht A v cht B trongphn ng

EA, EB l ng lng gam ca cht A v B

nh lut ng lng cho php tnh khi lng mt cht trong phnng nu bit ng lng ca cc cht v khi lng tc dng cacht kia. V d, tnh khi lng kh clor tc dng ht vi 3,45g natri,bit ENa = 23; ECl = 35,5. p dng h thc nu trn d dng tm thy:

35,5

m

233,45g Cl= mCl =

2335,53,45g = 5,33g

Vi khi nim nng ng lngl s ng lng gam cht tan ctrong 1 lt dung dch (k hiu N vit sau tr s ng lng), nh lutng lng c s dng rng ri trong php phn tch chun .Chng hn, cn bao nhiu mL dung dch kim B (t l VB) trungha ht VA ml dung dch acid A c nng ng lng l NA. Bitnng ng lng ca dung dch kim B l NB.

p dng nh lut ng lng: s ng lng ca cc cht trongphn ng phi bng nhau, ta c:

AA .N

1000

V = BB .N

1000V VB =

B

AA

N

.NV

Phng trnh trn c p dng cho tt c cc phng php phn tchth tch (phng php acid - base; phng php kt ta; phng php phccht; phng php oxy ha - kh).

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1.3.3. ngha ha hc ca khi nim ng lnglin quan trc tipn khi nim ha tr ca cc nguyn t. Trc y, ngi ta coi ha tr lkh nng ca mt nguyn t ca nguyn t c th kt hp hoc thay thbao nhiu nguyn t hydro hoc bao nhiu nguyn t khc tng ng.Nh vy, ng lng ca mt nguyn t l s n v khi lng (s phn

khi lng) ca nguyn t y tng ng vi mt n v ha tr. Gia nglng (E), ha tr (n) v khi lng nguyn t (A) ca nguyn t c mitng quan sau:

E =n

A

V d, oxy c ha tr 2, khi lng nguyn t 16, nn:

EO = 216

= 8

Nu nguyn t c nhiu ha tr th ng lng ca n cng thay itu thuc vo ha tr m n th hin trong sn phm to thnh sau phnng. V d, carbon c ha tr 2 v 4. phn ng: 2C + O2 = 2CO, carbon

th hin ha tr 2, nn EC = 212

= 6. Cn phn ng: C + O2 = CO2,

carbon th hin ha tr 4, nn EC = 412

= 3.

M rng khi nim ng lng cho cc hp cht, ta vn nhn ra ngha ha hc ca n l phn khi lng tng ng vi mt n v ha tr

m hp cht em trao i hoc kt hp vi cc hp cht khc trong phnng. Chng hn, H3PO4 = 98. Nu trong phn ng, phn t H3PO4 ch traoi 1 proton, hp cht c xem nh th hin ha tr 1, th = 98/1 =

98; nu trao i 2 proton, hp cht c xem nh th hin ha tr 2, th= 98/2 = 49; cn nu trao i c 3 proton th hp cht H

43POHE

43POHE 3PO4 c coi

l c ha tr 3 v phn khi lng tng ng vi 1 n v ha tr (tc nglng ca n) trong trng hp ny l: = 98/3 = 32,7.

43POHE

Cc nh ha hc hin ti quan nim: ha tr ca mt nguyn t l s

lin kt ha hc m mt nguyn t ca nguyn t c th to ra kthp vi cc nguyn t khc trong phn t.

Cng vi khi nim ha tr, ngi ta cng dng khi nim s oxy hacho cc ion hoc cho cc nguyn t trong hp cht. Tuy khng c nghavt l r rng, nht l trong cc phn t phc tp, nhng s oxy ha khtin dng cho nhiu mt thc hnh ha hc.

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Chnh v khi nim ha tr pht trin v m rng gn vi bn chtnhiu loi lin kt, nn theo , khi nim ng lng cng cn c cth cho cc trng hp (cch tnh ng lng ca cc hp cht c trnhby mc biu th nng ng lng di y).

2. Nhng khi nim c bn2.1. Nng dung dch. Cc cch biu th nng

Nng l cch biu th thnh phn nh lng ca mt dung dch.N c th biu th lng cht tan trong mt th tch xc nh ca dungdch, hoc lng cht tan trong mt khi lng xc nh ca dung dchhoc ca dung mi. Lng cht tan trong dung dch cng ln th nng cng ln v ngc li. Bng 1 tm tt cc loi nng thng c dngtrong ha hc v Y- Dc.

Bng1. Cc loi nng Loi nng K hiu nh ngha

Phn trm theo khi lng (KL) % (KL/KL) S g cht tan trong 100 g dung dch

Phn nghn theo khi lng (KL/KL) S g cht tan trong 1000 g dung dch

Phn trm theo th tch (V) % (V/V) S mL cht tan trong 100 mL dung dch

Phn trm theo khi lng-th tch % (KL/V)S g (hoc s mg) cht tan trong 100mL dung dch

Phn nghn theo khi lng-th tch (KL/V) hoc g/L S g cht tan trong 1000 mL (= 1 L)dung dch

Mol M, mol/L S mol cht tan trong 1 L dung dch

ng lng NS ng lng gam cht tan trong 1L dung dch

Di y l mt s v d c th v cc loi nng hay gp.

2.1.1. Nng %, theo khi lng/khi lng

V d: Dung dch KNO3 10% c ngha l c 10 g KNO3 trong 100 gdung dch. Dung dch cc acid c H2SO4, HNO3 v HCl bn trn th trngc nng tng ng bng 96%, 65% v 36%.

Bi v o th tch dung dch d dng hn o khi lng, nn ngi tathng ghi khi lng ring km theo cho loi dung dch ny, chuyni t khi lng cht cn ly sang th tch dung dch cn ong. V d, HCl36% c D = 1,179 g/mL ( 20oC).

Dung dch NaCl 9 c ngha l c 9 g NaCl trong 1000 g dung dch.

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2.1.2. Nng %, theo khi lng/th tch(thng c vit g/100 mL;g/L...):

V d, dung dch glycerin 10 g/100 mL, glucose 50 g/L c ngha l c10 g glycerin trong 100 mL dung dch, c 50 g glucose trong 1 lt dung dchcho 2 dung dch tng ng k.

2.1.3. Nng mol/L (M)

Mol l mt lng cht cha s ht cng kiu cu trc (phn t,nguyn t, ion, electron, proton...) bng s Avogadro 6,022.1023. Thng sdng l mol/L, s phn t gam/L.

Cc dung dch c nng mol bng nhau th cha cng s lng htcht tan trong nhng th tch dung dch bng nhau (ch : ht cht tanphi cng kiu cu trc).

V d, dung dch NaOH 2M, ngha l trong 1 lt dung dch ny c 2

mol hay 2 mol 40 g/mol = 80 g NaOH.

Dung dch cha phenobarbital 0,001M v NaCl 0,1M, ngha l trong 1lt dung dch nh th c 0,001 mol 232,32 g/mol = 0,2323 g phenobarbital(C12H12N2O3 = 232,32) v 0,1 mol 58,45 g/mol = 5,8450 g NaCl (M =58,45).

Trong 1 lt dung dch NaCl 1M c 1 mol 58,45 g/mol = 58,45 g NaCl.Xem NaCl in ly hon ton thnh cc ion, th trong 1 lt dung dch nhth cng c 1 mol ion Na+ (23 g Na+) v 1 mol Cl- (35,45 g Cl).

Ngc li, dung dch Na2CO3 1M c trong 1 lt dung dch ca n 1 molCO32 (60 g CO3

2) v 2 mol Na+ (2 mol 23 g/mol = 46 g Na+), vi iu kingn ng rng trong dung dch, c 1 phn t natri carbonat th in ly ra 1ion CO3

2 v 2 ion Na+.

2.1.4. Nng ng lng (N)

V d, H2SO4 0,5N l dung dch cha 0,5 ng lng gam H2SO4trong 1 lt dung dch.

Khi nim ng lng ca mt cht xut pht t nh lut ng

l

ng ca Dalton nu ra nm 1792. Gi

ng l

ng ca mt cht l E, tac th nu cc cng thc tnh E trong cc phn ng trao i v oxy ha khnh sau:

Khi lng nguyn t

Ha trEnguyn t=

V d: 82

16Eoxy ==

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Khi lng ion

| in tch ion |E

ion=

V d, 93

27E ==+ 3Al

482

96E == 24SO

Khi lng phn t acid

S ion H+ in ly t mt phn t acidE

acid=

V d, 36,451

36,45E ==HCl

492

98E ==

42SOH

Khi lng phn t base

S ion OH in ly t mt phn t base-Ebase =

V d: 401

40E ==NaOH

Khi lng phn t mui

|in tch ion (dng hoc m)| x S ion (dng hoc m)E

mui=

V d: 5723

342E =

=

342 )(SOAl

Khi lng tiu phn (phn t, nguyn t, ion)

S electron nhn (hoc cho) ca mt tiu phndng oxy ha (hoc dng kh)

EOX(Kh) =

y, EOX(Kh) l ng lng ca dng oxy ha, hoc ca dng kh.

V d, tm ng lng ca cht oxy ha v cht kh trong phn ng:

2KMnO4 + 10FeSO4 + 8H2SO4 = 2MnSO4 + 5Fe2(SO4)3 + K2SO4 + 8H2O

Cn c theo s electron m mt phn t KMnO4 nhn bng 5 v selectron m mt phn t FeSO4 cho bng 1, ta xc nh c ng lngca cht oxy ha l:

31,65

158E ==

4KMnO

v ng lng ca cht kh l:

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151,81

151,8E ==

4FeSO

V ha tr ca nguyn t, s H+ hay OH in ly ca acid hay base, selectron nhn hoc cho ca cht oxy ha hoc cht kh c th thay i tutheo iu kin ca phn ng, nn ng lng ca mt cht cng c nhng

gi tr bin i.ng lng l mt i lng khng c th nguyn. Trong ha hc

ngi ta thng dng:

ng lng gam ca mt cht l khi lng ca cht biu dinbng gam v c tr s bng ng lng ca n.

Mili ng lng gam, k hiu mE, bng 1/1000 ng lng gam vly n v khi lng l miligam.

2.2. S in ly ca n

c. Thang pH2.2.1. S in ly ca nc

Nc l dung mi lng tnh, va cho v va nhn proton:

H2O

H2O H+

H2O H2O

+

+

Acid 1 Base 2

OH-

H3O+

H3O+ OH-

+

+

H+

Acid 2 Base 1

v tng ng vi 2 cp acid - base lin hp theo thuyt Brnsted -Lowry: H2O/OH

v H3O+/H2O.

Mc d s in ly ca nc rt b, ngi ta vn o c dn inca n v xc nh c gi tr ca hng s cn bng theo nh lut tcdng khi lng:

18-

2

2

-

3 3,24.10]OH[

][OH]O[HK ==

+

( 25oC)

K [H2O]2 = 3,24.10-18 ( 18

1000)2 = Kn = [H3O+] [OH] = 1,0.10-14

Hng s Kn gi l tch s ion ca nc. Tch s ny thay i theonhit .

V mt ion H3O+ v mt ion OH c phn ly t mt phn t H2O, do

trong nc nguyn cht:

[H3O+] = [OH] = 1410 = 107 mol/L

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(Nng nc nguyn cht =02,18

1000 55,5M, vy c mi 555 triu

phn t nc ch c 1 phn t in ly ra cc ion). Da vo cn bng in lyca nc, ngi ta nh ngha dung dch acid, base v trung tnh tu theo ln tng i gia [H3O

+] v [OH]:

Dung dch Gii hn chung 25oC

Acid [H3O+] > [OH] [H3O

+] > 10-7 [OH] < 10-7

Trung tnh [H3O+] = [OH] [H3O

+] = 10-7 [OH] = 10-7

Base [H3O+] < [OH] [H3O

+] < 10-7 [OH] > 10-7

V Kn l hng s nhit nht nh, nn khi bit nng ca mttrong hai ion, ta c th tnh c nng ion kia.

V d: Bit [H3O+] ca mt dung dch bng 3,0.10-4M. Tnh [OH] vcho bit dung dch l acid, trung tnh hay base?

Gii:

[OH] =4-

-14

3

n

100,3

10

]OH[

K

=

+= 3,3 10-11 M

y l dung dch acid v [H3O+] > [OH].

2.2.2. Thang pH

Nng H3O+ trong dung dch nc c th bin i trn mt phm virng t 10M n 10-15M, gy kh khn v di dng trong tnh ton, do Srensen ngh dng i lng pH biu th tim nng ion hydro(hydrogen ion potential) vi nh ngha:

pH = -lg[H3O+] hoc [H3O

+] = 10-pH

v pOH = -lg[OH] hoc [OH] = 10-pOH

V Kn = [H3O+][OH] = 1,0 10-14 nn ngi ta cng hay dng i lng:

pKn = -lgKn = -lg([H3O+][OH]) = -lg[H3O

+] - lg[OH] = pH + pOH = 14

( 25oC)

Thng thng ngi ta ch s dng thang pH, cc i lng khc csuy ra theo phng trnh quan h (Bng 2).

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Bng 2. Quan h gia [H3O+], pH, pOH v [OH].

1514

1514

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-7

10-6

10-5

10-4

10-3

10-2

10-1

110

110

-1510-1410

-13

10-12

10-11

10-10

10-9

10-7

10-6

10-5

10-4

10-3

10-210

-1

110

1

H

O

nng

3

+

OHn

ng

-

Trung tnh

base

tng

acidtng

[H O ]3

pH pOH [OH ]+ -

Ch : V Kn ph thuc nhit nn pKn, pH, pOH ca nc nguyn

cht cng thay i theo nhit (Bng 3).

Bng 3. Tch s ion (Kn) ca nc nguyn cht mt s nhit .

Nhit (oC) Kn 10-14 pKn pH = pOH

0 0,11 14,96 7,48

10 0,29 14,54 7,27

25 1,00 14,00 7,00

50 5,66 13,25 6,62

100 51,30 12,29 6,15

300 400,00 11,40 5,70

2.2.3. Cht ch th acid - base

C hai cch thng dng o pH trong phng th nghim l o bng

my (pH-meter) v o bng cht ch th acid-base (cn gi l cht ch thmu). Nguyn l o pH bng my s cp chuyn mc ring.

Cht ch th acid-base l nhng thuc th c bit c mu sc thay itu theo nng ion H3O

+ trong dung dch, tc l tu theo pH mi trng.Ni chung, c th xem cht ch th mu l mt acid hu c yu m dngacid (k hiu HInd) c mu, gi tt l mu acid, khc vi mu ca dngbase lin hp vi n (Ind), gi tt l mu base. Nh vy, s thay i muca ch th l do s bin i cu trc phn t gia hai dng acid v base.

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Trong dung dch, s bin i gia hai dng th hin qua cn bng inly ph thuc vo pH:

HInd + H2O H3O+ + Ind

Acid 1 Base 2 Acid 2 Base 1

Mu acid Mu baseTrong vng pH chuyn mu, mu ca dng acid v dng base ang

trong qu trnh chuyn i nhau: mu ca dng ny dn dn sang mu cadng kia, hoc ngc li.

Bng 4 cho bit khong pH chuyn mu ca mt s ch th acid - basethng gp.

Bng 4. Mu, khong pH chuyn mu ca mt s ch th acid - base hay gp

Mu

Cht ch th Acid Base Khong pH chuyn mu

Da cam Methyl (Heliantin) Hng Vng 3,1 4,4

Qu Xanh 5,0 8,0

Phenolphthalein Khng mu 8,2 10,0

Vng Alizarin Vng Tm 10,0 12,0

2.3. iu kin kt ta v ha tan. Tch s tan

Khi nim v Tch s tanKhi ha tan mt cht in ly t tan MmXn vo nc s to ra mt dung

dch bo ha, trong tn ti cn bng d th gia lng cht rn cn dv cc ion ca n trong dung dch:

MmXn(r)

(rn)

mMn+ + nXm-

(dung dch)

Lng MmXn tan vo dung dch rt t, gi l tan S, c coi lin ly hon ton thnh cc ion Mn+ v Xm. Ging nh cc h cn bng

khc, i vi dung dch bo ha ca cht ang xt ta c biu thc tc dngkhi lng:

)r(nm

n-mmn

]XM[

][X][MK

+

=

Nng pha rn l hng s, nn:

[Mn+]m [Xm]n = K [MmXn] (r) =nmXM

TT

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K hiu sau cng gi l tch s tan ca MmXn. Nh vy:

Tch s nng cc ion ca cht in ly t tan trong dung dch boha, mi nng c lu tha tng ng vi h s trong phng trnhin ly, l mt hng s nhit nht nh gi l tch s tan, k hiu T.

Cc gi tr ca T cho bit tan tng i ca cc hp cht ion. Khicc cht in ly ra cng s ion, ngha l m+n nh nhau, th T ca cht nocng ln, tan ca n cng ln, v ngc li. iu ny c th hin quaBng 5.

Bng 5. Quan h gia T v tan 25oC ca mt s hp cht.

S ion Cng thc cation/anion T tan (M)

2 MgCO3 1/1 3,5 10-8 1,9 10-4

2 PbSO4 1/1 1,6 10-8 1,3 10-4

2 BaCrO4 1/1 1,2 10-10 1,4 10-5

3 Ca(OH)2 1/2 6,5 10-6 1,2 10-2

3 BaF2 1/2 1,5 10-6 7,2 10-3

3 CaF2 1/2 3,2 10-11 2,0 10-4

3 Ag2CrO4 2/1 1,1 10-12 8,7 10-5

iu kin kt ta hay ha tan mt cht in ly t tan:Mt cht s kt ta khi tch s nng cc ion ca n trong dung dch

ln hn tch s tan. Ngc li, khi tch s nng cc ion cn b hn tch stan th cht cha kt ta, hoc nu c ta th ta s tan ra.

V d:

Cho bit kt ta c hnh thnh hay khng trong cc trng hp sau:

a) Trn ln 0,100 L Ca(NO3)2 0,30 M vi 0,200 L NaF 0,060 M.

b) Trong nc mt dng sng tm thy [Ca2+] = [PO43] = 1,0 10-9 M.

Choo bit = 3,2 102CaF

TT -11 ; = 1,2 10243 )PO(Ca

TT -29.

Gii:

a) Cc ion c mt trong hn hp l Ca2+, Na+, NO3 v F. Ch c CaF2

l c th kt ta theo cn bng:

CaF2(r) Ca2+ + 2F-

Tnh nng mol/L cho cc ion:

S mol Ca2+ a vo hn hp = 0,30M Ca2+ 0,100L = 0,030 mol Ca2+

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v [Ca2+] =L0,200L100,0

mol030,0

+= 0,10 M Ca2+

S mol F a vo hn hp = 0,060M 0,200L = 0,012 mol F

v [F

] = L0,200L100,0

mol012,0

+ = 0,040M F

Trong hn hp, ta c tch s nng cc ion, k hiu Qm, l:

Qm = [Ca2+] [F]2 = 0,10 0,0402 = 1,6 10-4 > = 3,2 10

2CaFT -11

Vy, kt ta CaF2 phi c to thnh.

b) Tm Qm ca Ca3(PO4)2 theo cn bng:

Ca3(PO4)2 (r) 3Ca2+ + 2PO4

3-

v s dng cc d liu cho, ta c:

Qm = [Ca2+]3 [PO4

3]2 = (1,0 10-9)3 (1,0 10-9)2

= 1,0 10-45 < = 1,2 10243 )PO(Ca

TT -29.

Vy, cha th hnh thnh kt ta Ca3(PO4)3 dng sng ang xt.

2.4. Phn ng oxy ha - kh

2.4.1. Cc nh ngha

Phn ng oxy ha - kh l phn ng c s chuyn dch electron giacc cht phn ng, do lm bin i s oxy ha ca cc nguyn t.

Cht oxy ha (phn t, nguyn t, ion) l cht nhn electron v gims oxy ha, n l cht b kh.

Cht kh (phn t, nguyn t, ion) l cht cho electron v tng s oxyho, n l cht b oxy ha.

Theo suy ra: s kh l s nhn electron, s oxy ha l s cho i electron.Rt cn lu khng nhm ln cc thut ng: cht oxy ho, s oxy

ha, cht kh, s kh.

V d: trong dung dch nc xy ra phn ng:

Fe + Cu2+ Fe2+ + Cu

Ion Cu2+ nhn electron (t Fe) l cht oxy ha, s oxy ha ca n gimt +2 n 0, n b kh v gi l s kh ion Cu2+ (bi Fe).

St cho electron nn l cht kh, s oxy ha ca n tng t 0 n +2,n b oxy ha v gi l s oxy ha st (bi Cu2+).

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2.4.2. S oxy ha (S.O)

S oxy ha (cn gi l mc oxy ha, trng thi oxy ha) l in tchhnh thc ca nguyn t trong n cht, ion hay hp cht khi qui ccc cp electron dng chung lch hon ton v nguyn t c min ln hn.

Ch rng, S.O ca nguyn t c gi tr i s khc ha tr. S.O cth l s m, s dng hoc bng khng. Tri li, ha tr tnh theo selectron tham gia lin kt nn ch c gi tr dng.

S S.O ca mt nguyn t c xc nh theo nhng quy tc sau:+ Quy tc chung:1. Nguyn t trong n cht (Na, Cu, O2, N2, S): S.O = 0.

2. Nguyn t trong ion n nguyn t: S.O = in tch ion.

3. Tng i s S.O ca cc nguyn t trong phn t = 0, cn trong ionnhiu nguyn t = in tch ion.

+ Quy tc c th cho cc nguyn t hoc nhm nguyn t trong Bngtun hon:

1. Nhm IA: S.O = +1 trong tt c cc hp cht.

2. Nhm IIA: S.O = +2 trong tt c cc hp cht.

3. Hydro: S.O = +1 trong cc hp cht vi phi kim

S.O = -1 trong cc hp cht vi kim loi v Bor

4. Fluor: S.O = -1 trong mi hp cht

5. Oxy: S.O = -1 trong cc hp cht peroxyd

S.O = -2 trong tt c cc hp cht khc (tr vi fluor)

6. Nhm VIIA: S.O = -1 trong cc hp cht vi kim loi, vi phi kim(tr vi oxy) v vi cc halogen khc pha di nhm.

+ Lu :1. S.O dng cao nht ca cc nguyn t trong cc nhm chnh A bng

s th t ca nhm (tr O v F).2. S.O m thp nht ca cc phi kim v mt s kim bng s th t

ca nhm tr 8.

V d: Lu hunh c S.O dng cao nht l +6 (v nguyn t S nhm VIA) nh trong hp cht SF6; v c S.O m thp nht = 6 - 8= -2 nh trong FeS.

3. V nguyn tc, xc nh s oxy ha cn phi bit cu to phn tv m in ca cc nguyn t. m in c th suy ra gn ng t v

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tr ca nguyn t trong Bng tun hon. Cn nu khng bit r cu tophn t th S.O xc nh c t cc nguyn tc nu c th l S.O gi.Chng hn, t S.O ca Lu hunh l x, tm c S.O ca n trong S2O8

2-qua phng trnh: (x.2) + (-2.8) = -2 x = +7. y l s oxy ha gi, v Luhunh nhm VIA, S.O cao nht ca n ch l +6 ph hp vi cng thc

cu to:O

S

O O

O O

S

O

O O

O

S

O

O O

O

S

O

O O

hocO

S

O O

O O

S

O

O O

O

S

O O

O O

S

O

O O

O

S

O

O O

O

S

O

O O

hoc

Hn na, cn gp s oxy ha gi v l, nh S trong Na2S4O6 c S.O = +2,5.

Tuy nhin, S.O tht hay gi u c gi tr nh nhau trong cn bngphng trnh ca phn ng Ox-Kh.

2.4.3. Cn bng phn ng oxy ha kh theo phng php S.O cthc hin theo cc bc sau:

1. Vit cc cht u (cht phn ng) v cc sn phm. V d:

HClO3 + P HCl + H3PO4

(D nhin cht u bit, nhng sn phm l g th phi da vo ccphp phn tch ha hc hoc cn c vo quy lut bin i ca cc nguyn tv hp cht cc iu kin).

2. Xc nh S.O ca cc nguyn t trc v sau phn ng. v d

trn, tm thy:HCl5+O3 + P

0 HCl1- + H3P5+O4

3. Tm s electron m mt phn t cht kh cho v s electron m mtphn t cht oxy ha nhn, t lp phng trnh trao i electron tmh s chnh ca cht kh v cht oxy ha. Tip v d trn, thnh lp:

+

+

+

15

50

Cle6Cl5

Pe5P6

Ch : cc h s chnh phi c mt bi s chung nh nht biu th tngs electron m cht kh cho bng tng s electron m cht oxy ha nhn.

4. t h s chnh ph hp vo cc cht kh v cht oxy ha ban u,kim tra s nguyn t ca mi nguyn t 2 v phng trnh cn bngchng nhng cha cn ch n s nguyn t H v O (nu 2 nguyn tny khng trc tip l cht kh hay cht oxy ho). Tip theo v d trn,thu c:

5HClO3 + 6 P = 5HCl + 6 H3PO4

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5. Kim tra s nguyn t H 2 v tm s phn t nc tham giahoc to thnh. Vi v d ang xt, cn 9 phn t H2O tham gia phn ng.

Vy:

5HClO3 + 6P + 9H20 = 5HCl + 6H3PO4

6. Kim tra li s nguyn t O 2 v v tin rng thc cht phngtrnh c cn bng.

Vi 6 bc tin hnh nh trn, mi phng trnh phn ng oxy ha -kh vit di dng phn t u c th c cn bng. Tuy nhin, nhiutrng hp khng cn thc hin cc bc v khi quen th ch cnnhm tnh trn mt phng trnh phn ng.

Lu : Khi vit phng trnh phn ng cn bng di dng phngtrnh ion th in tch 2 v phi bng nhau

2.5. Phc cht

2.5.1. nh ngha

Bn cnh cc mui n gin nh K2SO4, Al2(SO4)3, KI, HgI2, KCN,Fe(CN)2... cn c cc mui kp (gi l phn) nh: K2SO4.Al2(SO4)3.24H2O(phn chua), (NH4)2SO4.FeSO4.6H2O (phn st amoni hay mui Mohr)...

Mui n gin v mui kp ging nhau ch, khi ha tan trong nc,chng in ly hon ton ra cc ion n gin. V d:

K2SO4 2K+ + SO4

2-

(NH4)2SO4.FeSO4.6H2O 2NH4+ + Fe2+ + 2SO42- + 6H2OT lu, ngi ta cng bit nhiu hp cht phc tp khc c thnh

phn ging mui kp, nh 2KI.HgI2, Zn(NO3)2.4NH3, nhng trong ncchng in ly cho nhng ion phc tp, v d:

2KI.HgI2 2K+ + [HgI4]

2-, nn phn t c vit: K2[HgI4]

Zn(NO3)2.4NH3 [Zn(NH3)4]2+ + 2NO3

-, nn phn t c vit:[Zn(NH3)4](NO3)2.

Cc hp cht kiu ny c t tn l phc cht vi nh ngha:

Phc cht l nhng hp cht phn t m trong s t hp cc cu tca chng to nn nhng ion phc tch in dng hay m, nhng ion nyc kh nng tn ti trong dung dch cng nh trong tinh th.

2.5.2. Cu to, danh php v cc hng s ca phc cht

Cc thnh phn ca phc cht c th hin qua s , v d viK2[HgI4], nh sau:

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Cu ngoi Ion trung tm Phi t

(2K+ ) (Hg2+ ) (4I-)

Cu ni(ion hc)

K2[HgI4]

Cch c tn phc cht phi tun theo quy nh cht ch, c trnhby phn ph lc (cui gio trnh ny).

Trong dung dch nc, phc cht in ly hon ton thnh cc ion cungoi v cu ni. V d:

K2[HgI4] 2K+ + HgI4

2-

Sau , cu ni c th in ly yu tng nc ra cc phi t ng vi cchng s cn bng in ly, thng gi l hng s khng bn k ca phc. V d:

HgI42 HgI3

+ I]HgI[

]I][HgI[k

=2

4

31 = 5,0.10

-3

HgI3 HgI2 + I

]HgI[

]I][HgI[k

=3

22 = 1,6.10

-4

HgI2 HgI+ + I

]HgI[

]I][HgI[k

2

3

+

= = 1,0.10-11

HgI+ Hg2+ + I]HgI[

]I][Hg[k

+

+

=2

4 = 1,2.10-13

Phng trnh in ly tng cng :

HgI42 Hg2+ + 4I

]HgI[

]I][Hg[k

+

=2

4

42

= k1.k2.k3.k4 = 9,6.10-31

k1, k2, k3, k4 l hng s khng bn nc, cn k l hng s khng bn tngcng. k cng ln, phc cng khng bn, v ngc li.

Nu xt qu trnh hnh thnh, s to thnh phc cng theo tng ncv tn ti cc cn bng. V d:

Hg2+ + I HgI+]I][Hg[

]HgI[K

+

+

=21

HgI+ + I HgI2]I][HgI[

]HgI[K

+= 22

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HgI2 + I HgI3

]I][HgI[

]HgI[K

=2

33

HgI3 + I HgI4

2]I][HgI[

]HgI[K

=3

2

44

Phng trnh to phc tng cng:

Hg2+ + 4I HgI42-

42

2

4

]I][Hg[

]HgI[K

+

=

K1, K2, K3, K4 l hng s bn hay hng s to phc nc, cn K l hngs to phc tng cng. K cng ln, phc cht cng bn, v ngc li.

Gia hng s bn v hng s khng bn c mi quan h nghch o, do :

k1.K4 = k2.K3 = k3.K2 = k4.K1 = k.K = 1

Ch : Du ngoc vung [ ] trong phc cht ch cu ni, cn trongcc biu thc ca k hoc K ch nng mol/L ca cc cu t.

Bi tp (Bi 1)

1.1. Carbon monooxyd cha 43% carbon theo khi lng. Hy vitcng thc ha hc ca oxyd y v biu th t l carbon/oxyd theo

cc n v kg, g v khi lng nguyn t.1.2. Lu hunh (VI) oxyd cha 25% mol lu hunh. Cch biu th t l

no sau y l ng, v sao?

;molSO100

molS25

3

;100

25

3kgSO

kgS ;LitSO100

LitS25

3

a) b) c)

1.3. Xc nh t l % ca mi nguyn t trong Trimagnesi phosphat.

1.4.Tnh t l % ca H v C trong:

a. Benzen C6H6

b. Acetylen C2H2

c. So snh kt qu tnh a) vi b) v gii thch

d. i lng no phn bit benzen v acetylen.

1.5. Tnh s nguyn t oxy trong 300 gam CaCO3?

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1.6. Tm cng thc thc nghim ca cc cht c t l % ca cc nguynt nh sau:

a) Fe = 63,53%; S = 36,4%

b) Fe = 46,55%; S = 53,45%

c) Fe = 53,73%; S = 46,27%1.7. nh ngha ng lng trong phn ng trung ha v trong phn

ng oxy ha-kh khc nhau nh th no?

1.8. Tnh th tch ca dung dch 0,232 N cha:

a. 3,17 E cht tan

b. 6,5 E cht tan.

1.9. Tnh nng ng lng ca mi dung dch sau:

a. 7,88 g HNO3 trong mi lt dung dch.b. 26,5 g Na2CO3 trong mi lt dung dch.

1.10. C bao nhiu ng lng cht tan trong:

a. 1L dung dch 2 N

b. 1L dung dch 0,5 N

c. 0,5 L dung dch 0,2 N

1.11. Cho bit nng ng lng ca dung dch H3PO4 0,300Mtrong phn ng sau:

H3PO4 + 2OH- HPO4

- + 2H2O

1.12. Tnh th tch nc cn thm vo 250mL dung dch 1,25 N thuc dung dch c nng 0,500 N.

1.13. Cn my mL dung dch NaOH 6,0 N trung ha ht 30mLdung dch HCl 4,0 N?

1.14. Xc nh nng ng lng ca dung dch H3PO4 nu 40,0mLdung dch ny trung ha va 120mL dung dch NaOH 0,531 N.

1.15. Mt dung dch KMnO4 1,752 N b kh thnh MnO2. Tnh nng

mol/L ca dung dch .1.16. Cn bng phng trnh phn ng sau:

Sn + HCl + HNO3 SnCl4 + NO + ....

V cho bit:

a. 1mol Sn cha my ng lng?

b. 1mol HNO3 cha my ng lng?

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1.17. Cn bng phng trnh phn ng sau:

KMnO4 + KI + H2SO4 K2SO4 + MnSO4 + I2+ ....

V cho bit:

a. Cn bao nhiu gam KMnO4 pha 500mL dung dch KMnO4

0,250 N?b. Cn bao nhiu gam KI pha 25,0mL dung dch KI 0,360 N?

1.18. Tm s oxy ha ca mi nguyn t (tr oxy) trong mi hp cht sau:

a) P2O74- ; b) C3O2 ; c) MnO4

- ; d) MnO42- ; e) VO2

+ ;

f) UO22+ ; g) ClO3

- ; h) S2O32- ; i) CS2 ; j) S4O6

2- ;

k) S2Cl2

1.19. Cn bng cc phng trnh phn ng sau:

a. HNO3 + H2S NO + S +...b. KMnO4 + KCl + H2SO4 MnSO4 + K2SO4 + Cl2 +...

c. K2Cr2O7 + HCl CrCl3 + Cl2 + KCl + ....

d. Zn + NaNO3 + NaOH Na2ZnO2 + NH3 + ...

e. HgS + HCl + HNO3 H2HgCl4 + NO + S + ...

f. KMnO4 + H2SO4 + H2O2 MnSO4 + O2 + K2SO4+ ...

g. CrI3 + KOH + Cl2 K2CrO4 + KIO4 + KCl +...

Hy c v vit tn tt c cc cht c trong cc phn ng trn theoDanh php ca Dc in Vit Nam.

1.20. a) in nhng gi tr thch hp vo tt c cc cn trng cabng sau:

Dung dch [H3O+] [OH-] pH pOH

1 5.10-4

2 3.10-5

3 6

4 12

b) Cho 3,31 g Pb(NO3)2 vo 1 lt dung dch th nhng dung dch notrong bng trn c kt ta Pb(OH)2?

Cho bit: = 102)OH(Pb

TT -12

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1.21. Tnh pH ca dung dch 1,0.10-3 M ca mi cht sau, gi thit cccht tan l in ly hon ton.

a) HCl b) NaOH c) Ba(OH)2 d) NaCl

1.22. Tnh pH v pOH ca mi dung dch sau, gi thit cc cht l

in ly hon ton.a. HNO3 0,00345 M

b. HCl 0,000775 M

c. NaOH 0,00886 M

1.23. Tnh pH ca 500mL dung dch cha 0,050 mol NaOH.

1.24. Tnh [H3O+] cc dung dch c pH bng:

a) 4 b) 7 c) 2,50 d) 8,26

1.25. Cho bit gi tr TAgCl, nu tan ca AgCl trong n

c bng1,0.10-5M.

1.26. Tm tan S ca Mg(OH)2 trong nc. Bit = 1,2.102)OH(MgT-11.

1.27. Dung dch bo ha Mg(OH)2 trong nc c pH bng my?

Bit = 1,2.102)OH(Mg

T -11.

1.28. Hy tnh tan cu AgCl trong dung dch AgNO3 0,20M.

1.29. tan ca PbSO4 trong nc l 0,038 g/L. Tnh .4PbSOT

1.30. tan ca Ag2CrO4 trong nc bng 0,044g/L. Tnh .42CrOAgT

1.31. Tnh tan ca Fe(OH)3 trong dung dch nc c pH = 8,0.

Bit = 1,0.103)OH(Fe

T -36.

1.32. Xc nh tan ca AgCl trong dung dch BaCl2 0,10M.

Bit TAgCl=1,0.10-10.

1.33. tan ca Fe(OH)2 trong nc l 2.10-5mol/L. Tnh gi tr ca

.2)OH(Fe

T

1.34. Tnh khi lng (theo gam) ca PbI2 ha tan trong:

a. 500mL nc

b. 500mL dung dch KI 0,10 M

c. 500mL dung dch cha 1,33 g Pb(NO3)2

Cho bit = 1,4.102PbI

T -8.

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1.35. Bit cc hp cht phn t di y u l phc cht:

a. CaF2.ZnF2 vi Ca2+ cu ngoi.

b. PtCl4.5NH3 vi 3Cl- cu ngoi

c. 4NaCN.Fe(CN)2 vi tt c CN- cu ni

d. 3KCN.Fe(CN)3 vi c 6CN- cu ni

Hy vit cng thc phn t ca cc hp cht trn di dngphc cht (cu ni c t trong du ngoc vung [ ]). Xc nhin tch ca ion trung tm v in tch ca cu ni.

1.36. c tn cc phc cht bi 35.

1.37. Vit phng trnh in ly v biu thc ca cc hng s khngbn nc v tng cng ca cc phc sau:

a) NH4[Ag(CN)2]b) K3[Fe(SCN)6]

1.38. So snh cc hng s cho bit phc no bn hn trong mi cpsau y:

a. [Zn(NH3)4](OH)2 v [Cu(NH3)4](OH)2 c hng s khng bn kln lt l 10-10 v 10-13.

b. Na[Ag(CN)2] v K[Ag(SCN)2] c hng s to phc K ln ltbng 1021,1 v 1011,3.

c. HgBr+ v HgI+ c hng s to phc nc K1ln lt bng 109 v 1012,9.

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Bi 2

i cng v Phn tch nh tnhcc ion trong dung dch

Mc tiu

1. Gii thch c s khc nhau gia cc phng php trong phn tch nh tnh: Phng php ha hc v phng php vt l - ha l Phn tch t v phn tch kh Phn tch ring bit v phn tch h thng

2. Trnh by c s khc nhau gia: Phn ng tch v phn ng xc nh nhy tuyt i v nhy tng i ca mt phn ng Thuc th nhm, thuc th chn lc v thuc th c hiu

3. Lp c s phn tch tng qut 6 nhm cation theo phng php acid-base4. K c tn cc thuc th nhm anion v vit phn ng minh ha.

Theo nh ngha rng, nhim v ca phn tch nh tnh l s dngcc phng php phn tch (ha hc hay vt l-ha l) cho bit: cnhng nguyn t, phn t, nhm nguyn t trong phn t, hay ion notrong mt mu vt cn nghin cu.

Gio trnh ny ch yu ch gii thiu phn phn tch nh tnh cc ionv c trong dung dch.

1. Cc phng php phn tch nh tnh

1.1. Phng php ha hc: L phng php nh tnh da trn cc phnng ha hc. Phng php ny khng cn trang thit b phc tp nn titkim v d thc hin. Tuy nhin, n i hi thi gian tng i di v lngcht phn tch tng i ln.

1.2. Phng php vt l - ha l: L phng php phn tch nh tnh datrn cc tnh cht vt l v ha l ca mu vt cn kim nghim. V d, ccphng php thng dng l:

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a. Phng php soi tinh th: Dng knh hin vi pht hin cc tinhth c mu sc v hnh dng c trng ca mt hp cht. Chng hn, ionNa+ to tinh th hnh mt nhn mu vng lc nht vi thuc th Streng.

b. Phng php so mu ngn la: t cc hp cht d bay hi ca ccnguyn t trn ngn la n gas khng mu ri quan st. Chng hn, ngn

la stronti cho mu son, kali mu tm, natri mu vng, bari mu lcnht.

c. Cc phng php dng c: L nhng phng php dng cc my,thit b hot ng theo nhng nguyn l xc nh phn tch nh tnh. Vd, sc k, quang ph pht x, quang ph hp th, hunh quang, cc ph.

Cc phng php vt l ha l c nhy v chnh xc cao,nhng i hi trang thit b phc tp.

1.3. Phn tch t v phn tch kh

a. Phn tch t: L phng php nh tnh c tin hnh vi ccdung dch. Mu vt rn cn kim nghim phi c ha tan trong nc,trong acid, trong dung dch cng thy hay trong cc dung mi hu c.

b. Phn tch kh: Tin hnh phn tch vi cc cht rn hoc vi dungdch bng ng li kh. Chng hn:

Th mu ngn la: Khi t mui Sr2+ hoc dung dch cha ion Sr2+,xut hin ngn la mu son.

iu ch ngc mu vi natri borat: ngc mu lam l c mui cobalt,ngc mu lc l c mui crom.

1.4. Phn tch ring bit v phn tch h thng

a. Phn tch ring bit:L xc nh trc tip mt ion trong hn hp nhiu ionbng mt phn ng c hiu phn ng ch xy ra vi ring ion . Ta c thly tng phn dung dch phn tch th ring tng ion m khng cn theomt th t nht nh no. Chng hn, xc nh Iod (cng dng ion I 3

-) trongdung dch bng h tinh bt, phn ng c hiu cho mu xanh.

Thc t, khng nhiu ion c phn ng tht c hiu. Do , phn tch

ring bit ch c s dng trong s kt hp vi phn tch h thngb. Phn tch h thng: L tin hnh xc nh ion theo mt th t nht nh.Trc khi xc nh mt ion phi loi b hoc kha li cc ion cn tr l ccion c phn ng vi thuc th ging nh ion cn tm.

Chng hn, ngi ta thng dng thuc th amoni oxalat (NH4)2C2O4 xc nh ion Ca2+ qua phn ng:

Ca2+ + C2O42- CaC2O4 mu trng

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Tuy nhin, Ba2+ cng cho phn ng tng t, do trc ht cn philoi ion ny (nu c) khi dung dch nh phn ng vi cromat trong mitrng acid acetic:

Ba2+ + CrO42- BaCrO4 mu vng

phn tch h thng mt hn hp nhiu ion, ngi ta thng dngcc thuc th nhm chia cc ion thnh nhiu nhm, mi nhm c th lichia thnh cc phn nhm, v cui cng c tch thnh tng ion ringbit xc nh. Trnh t tin hnh nh vy to nn nhng s phntch tng qut v s phn tch nhm.

2. Cc phn ng dng trong phn tch nh tnh

2.1. Cc loi phn ng

a. Phn ng theo bn cht ha hc:

Phn ng ha tan. V d:CaCl2/nc = Ca

2+ + 2Cl-

CaCO3 + 2HCl = CaCl2 + CO2 + H20

Phn ng kt ta. V d:Ag+ + Cl- = AgCl

Phn ng trung ha. V d:Ba(OH)2 + 2HCl = BaCl2 + 2H20

Phn ng to cht bay hi. V d:NH4NO3 + NaOH = NH3

+ NaNO3 + H20

Phn ng oxy-ha kh. V d:2Mn2+ + 5PbO2 + 4H

+ = 2MnO4- + 5Pb2+ + 2H20

Phn ng to phc. V d:Hg2+ + 4I- = [HgI4]

2-

b. Phn ng theo mc ch phn tch:

Phn ng tch: Nhm chia cc cht, cc ion thnh nhng nhm nh,hay tch ring mt ion, mt cht dng cho phn ng xc nh.

Phn ng c trng hay xc nh: Nhm tm mt ion khi n cc lp hay khi cn trong hn hp.

Phn ng to iu kin cho tch v xc nh, nh:+ Phn ng kha hay loi ion cn tr.

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+ Phn ng m kha hoc ph phc gii phng ion cn tm.+ Phn ng iu chnh pH mi trng ha tan, kt ta hoc trung

ha cht cn phn tch.

2.2 nhy v tnh c hiu ca phn ng

Cc phn ng dng trong phn tch nh tnh cn phi nhanh, nhy,c hiu, c du hiu d nhn bit (nh kt ta, to mu, mu thay itrong cc dung mi hay iu kin phn ng, sinh kh c c im ring ...),xy ra hon ton. Tuy nhin, ty theo mc ch phn tch m phn ngc la chn ch cn t mt vi yu cu c th, khng nht thit phi c cc c tnh nu. Chng hn, khi tch ring mt ion bng cch ktta th phn ng phi hon ton. Nhng ch nh tnh ion th khngcn phi nh vy.

Hai yu cu quan trng i vi mt phn ng nh tnh l nhy v

tnh c hiu.

2.2.1. nhy ca phn ng:L lng cht ti thiu c th pht hin cbng phn ng trong nhng iu kin xc nh. C 2 cch biu th nhy:

a. nhy tuyt i hay gii hn pht hin: L lng cht nh nht,thng tnh bng microgam (1 mcg = 10-6 g)trong mt mu em th, cnc pht hin bng mt phn ng no .

b. nhy tng i: L nng gii hn (hay pha long gii hn),thng tnh theo g/mL, cn c pht hin bng mt phn ng trong iu

kin xc nh.V d: Phn ng kt ta xc nh Na+ bng thuc th Streng trong

ng nghim c nhy tuyt i l 10 mcg, ngha l ti thiu phi c 10mcg Na+ trong mt mu em th. Mt khc, quan st c r rng trongng nghim th th tch dung dch mu em th t nht l 0,5 mL. V vy, nhy tng i bng 2.10-5 g (Na+)/mL.

Cng phn ng nhng thc hin bng cch soi tinh th di knhhin vi, th th tch dung dch mu th ch cn 0,001 mL, theo nhytng i vn l 2.10-5 g/mL (hay pha long l 1/50.000 so vi n v

nng g/mL), nh

ng nhy tuyt i s l 0,02 mcg (nhy hn 500 lnso vi phn ng trong ng nghim).

V d trn y cho thy, nhy ph thuc cch thc hin phn ng.Ngoi ra, nhy cn chu nh hng ca cc yu t nhit , nng thuc th, s c mt ca cc ion l...

C mt s cch lm tng nhy ca phn ng. Chng hn, dungdch iod rt long trong nc c mu vng kh nhn bit, nhng khi chitiod vo cloroform mu tm xut hin rt r rng.

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2.2.2. Tnh c hiu ca phn ng: L trong nhng iu kin xc nh, cth dng phn ng (hay thuc th) xc nh mt cht khi c mt cccht khc. Tnh c hiu ca mt phn ng c th biu th bng gi tr:

mtccnglionLng

pht hincnionLng=F

Tt nhin, F cng nh, phn ng cng c hiu.

V d: KI l thuc th c hiu ca ion Hg2+ v n cho ta mu sonHgI2 rt d nhn ra, d nng Hg

2+ rt nh nm ln trong nhiu ion khc.Hn na mu d dng bin mt nu cho d KI do to thnh phc[HgI4]

2- tan v khng mu.

2.3. Thuc th trong cc phn ng nh tnh

a. Yu cu ca thuc th trong phn tch: Phi tinh khit, nhy v c hiu.

tinh khit l yu cu quan trng nht. Cc thuc th ha hc xptheo tinh khit tng dn nh sau:

Loi k thut thng lm nguyn liu ban u. Loi tinh khit th nghim ha hc ni chung. Loi tinh khit phn tch. Loi tinh khit ha hc lm cht chun. Loi tinh khit quang hc dng trong phn tch quang ph.

b. Thuc th theo tc dng phn tch: gm cc loi

Thuc th nhm: L thuc th c tc dng ging nhau ln mt nhmcc ion. V d, HCl l thuc th ca nhm Ag+, Pb2+, Hg2

2+.

Thuc th chn lc: L thuc th c tc dng ging nhau trn mt sion m cc ion ny c th thuc cc nhm phn tch khc nhau. Chnghn, NH3 c th to phc tan v khng mu vi mt s ion nhiunhm phn tch.

Thuc th c hiu hay thuc th ring: L thuc th ch cho phnng c hiu vi mt ion hoc vi mt cht. V d, h tinh bt cho mu

xanh ch vi iod, dimethyglyoxim trong mi tr

ng amoniac to thnhch vi ion Ni2+ mt kt ta mu hng.

3. Phn tch nh tnh cation theo phng php acid-base

phn tch nh tnh cc cation, ngi ta c th dng ng li phntch ring bit hay phn tch h thng, thng thng l kt hp c hai cch ny.

Trong ha hc, ng li phn tch h thng cc cation trong dungdch c xy dng kh cht ch: t mt phn dung dch cn phn tch

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(cn gi l dung dch ban u, dung dch gc) ngi ta ln lt tch tngnhm, tng phn nhm, ri tch ring tng cation xc nh cc cation cmt trong dung dch.

C hai ng li ch yu phn tch h thng cc cation l ng litheo phng php dng H2S v ng li theo phng php acid-base.

ng li theo phng php dng H2S da trn s khc nhau v tan ca nhiu sulfid kim loi tch cc cation thnh 5 nhm. ng liny kh cht ch, cho kt qu chnh xc, pht hin trit cc cation k ckhi chng nm trong phc cht. Tuy nhin, ng li ny c nhc imch yu l H2S rt c hi, mi kh chu v trong qu trnh phn tchthng gp cc dung dch keo ca S rt kh x l. V th, ngy nay, phngphp dng H2S hu nh khng cn c s dng.

ng li phn tch h thng cation theo phng php acid-base chyu da trn kh nng to kt ta, to phc vi cc acid-base l HCl,

H2SO4, NaOH, NH4OH.Bng 6 v S 5 ch ra s hnh thnh 6 nhm cation c bn v ng

li phn tch tng qut. Nhm cation c bn tch li c phn tch thnhtng phn nhm, ri tng cation nhn bit nh cc phn ng xc nh hocphn ng vi thuc th c hiu (xem cc s cc bi tip sau).

Bng 6. S hnh thnh 6 nhm cation theo phng php acid-base

NhmThuc th

nhmCc Cation thuc

nhmSn phm to thnh vi thuc

th nhm

I HCl Ag+, Hg22+

, Pb2+

AgCl, Hg2Cl2, PbCl2Nhmacid II H2SO4 long

Ba2+, Sr2+

Ca2+, (Pb2+)BaSO4, SrSO4, CaSO4, (PbSO4)

IIINaOH d +

H2O2

Al3+, Cr3+, Zn2+

Sn2+, Sn4+

As3+, As5+

AlO2-, CrO4

2-, ZnO22-

SnO32-, AsO4

3-

IV (NaOH)Fe2+, Fe3+, Sb3+

Sb5+, Bi3+, Mn2+

Mg2+

Fe(OH)2, Fe(OH)3, Sb(OH)3Sb(OH)5, Bi(OH)3, Mn(OH)2Mg(OH)2

V NH4OH c, dCu2+, Cd2+, Hg2+

Co2+

, Ni2+

Cc phc amino

[Me(NH3)n]2+

n = 4, 6

Nhmbase

VI Khng c Na+, K+, NH4+

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S 5*: S phn tch tng qut 6 nhm cation theo phng php acid-base

Nhm I: (ta clorid)AgCl, Hg2Cl2, PbCl2

Nc ly tm +H2SO4 2 N

Nhm II: (ta sulfat)

BaSO4, CaSO4, (SrSO4)

Nc ly tm+ NaOH 2N d

(+ H2O2)

Nhm III: (nc ly tm cha oxoanion)

AlO2-, ZnO2

2-, (SnO32-, CrO4

2-)

Kt ta (oxyd, hydroxyd nhm(IV + V)

+ HNO3(+ H2P2)

Nc ly tm

+ Na2CO3 ti thong c

+ NH4OH c

(+ H2O2)

Ta HSbO3 (hoc Sb2O5.H2O)

Ho tan bng HCl c Xc nh Sb:

- Phn ng thy phn

- Thuc th Caille-Viel

(Phn tch theo s 2)

(Phn tch theo s 2)

(Phn tch theo s 1)

Nhm VI: (dung dch phntch): NH4

+, Na+, K+

Ly tm

+ HCl 6NLy tm

(Phn tch theo s 4)

Ly tm

Nhm IV: (ta hydroxyd)Fe(OH)2,Fe(OH)3,

Bi(OH)3,MnO2,Mg(OH)2

Ly tm(Sb3+,5+ c th xp nhm IV do to ta

hydroxyd/acid, khng to phc amoniacat/hoc xp ring

Ly tm

Nhm V: (nc ly tm cha phc amino)Cu(NH3)4

2+, Hg(NH3)42+

(Ni(NH3)42+,Co(NH3)6

2+,Cd(NH3)42+)

Dung dch phn tch cation

(Phn tch theo s 4)(Phn tch theo s 3)

* S th t (5) c ghi tng ng vi s 5 trong Phn 2. Thc hnh phn tchnh tnh

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4. Phn tch nh tnh anion

Do khng c thuc th nhm tht r rng, nn cng khng th phnchia mt cch cht ch ton b cc anion thnh nhng nhm ring phntch h thng ging nh cc cation.

Da theo tc dng, cc thuc th nhm anion c th c phn loitheo Bng 7.

Nh nhng phn ng ca thuc th trn nhm anion- ch yu l phnng kt ta v oxy ha kh, chng ta c th nhn bit chnh xc s c mthay vng mt nhiu ion.

V d, mt phn ng kt ta khng xy ra vi thuc th nhm AgNO3+ HNO3 2N, c ngha l cc anion tng ng Cl

-, Br-, I-, SCN- khng c mttrong dung dch cn phn tch.

Cn nu, mt phn ng oxy ha kh xy ra lm mt mu dung dch I2

th chc chn l dung dch phn tch c mt hay nhiu anion ca nhm S2-,SO3

2-, S2O32-, AsO3

3-.

Nh ch dn ca thuc th nhm, cc anion trong mt nhm c xcnh bng thuc th c hiu, hoc sau phn ng tch, c xc nh bngmt vi phn ng c trng.

Lu : V c nhiu cation gy ri phn ng nhm v phn ng xcnh, nn cc cation cn c loi b trc khi tin hnh phn tchanion. iu ny c th thc hin c bng cch chuyn dung dch phntch thnh nc soda (dung dch cha Na2CO3). Trong nc soda, hu ht

cc cation gy ri (thng l kim loi kim th, kim loi nng) b kt tadng carbonat hoc hydroxyd. Cch to nc soda thng thng l: 1 thtch dung dch phn tch (vi mL) + 1 th tch dung dch Na2CO3 (vi mL) +vi git NaOH c. Lc hoc ly tm. Dung dch trong sut cha cc aniondng cho phn tch gi l nc soda; v cch pha ch nh vy gi tt l lmnc soda.

Tuy nhin nu dung dch gc phn tch, hoc dung dch iu kintin hnh phn ng c trng, c tnh cht ca nc soda th c ththc hin ngay cc bc phn tch m khng cn lm nc soda na.

mc gio trnh ny, s anion c quan tm ch chia thnh 2nhm:

Nhm I: gm Cl-; Br-; I-; SCN-, S2O32- c tch ring bng thuc th

nhm AgNO3 + HNO3 2N

Nhm II: gm CO32-, SO3

2-; SO42-; AsO3

3-; AsO43-; PO4

3-; CH3COO-, SO3

2-,SO4

2- c xc nh theo phng php phn tch na h thng v phn tchtrc tip.

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S phn tch anion nhm I v nhm II c trnh by Bi 9 vBi 10 pha sau.

Bng 7. Phn loi thuc th theo nhm anion

STT Thuc th nhm Nhm anion Sn phm hoc du hiu phn ng

1 HCl 2N hay H2SO4 2NCO3

2-; CN-; S2-; SO32-

S2O32-; NO2

-; ClO-

To cc kh tng ng:CO2 (khng mu, lm c nc vitrong); HCN (mi hnh nhn); H2S (mithi); SO2 (mi sc mnh); SO2 v S;NO v NO2 (mu nu , kh th); Cl2(mu vng lc, kh th)

2BaCl2 + CaCl2 trongmi trng trung tnh

AsO33-; AsO4

3-; CrO42-;

ClO-; MnO4-; SO4

2-

;PO43-; BrO3

-; IO3-; F- ...

To kt ta tng ng:

Ca3(AsO3)2 trng; Ca3(AsO4)2 trng;BaCrO4 vng; Ba(MnO4)2 ; BaSO4trng; Ca3(PO4)2 trng; Ba(BrO3)2 trng;Ba(IO3)2 trng; CaF2 trng;...

3 AgNO3 + HNO3 2N SCN-; Cl-; Br-; I-

To kt ta tng ng:AgSCN trng; AgCl trng; AgBr vngnht; AgI vng r

4Hn hp Mg (NH4OH+ NH4Cl + MgCl2)

AsO43-; PO4

3-To kt ta tng ng:

MgNH4AsO4 trng; MgNH4PO4 trng

5 KI + H2SO4 2NCrO4

2-; AsO33-; MnO4

-;ClO-; ClO3

-; BrO3-; IO3

-;NO2

-

Gii phng I2(Nhn bit iod bng mu trong dungdch nc hoc trong cloroform, hocth bng h tinh bt)

6 Dung dch I2S2-; SO3

2-; S2O32-;

AsO33- Lm mt mu I2

7Dung dch KMnO4 +H2SO4 2N

S2-; SO32-; S2O3

2-; NO2-;

AsO33-; Cl-; Br-; I-; CN-;

SCN-Lm mt mu KMnO4

8Khng c thuc thnhm

NO3-; ClO4

-

5. Nhng k thut c bn trong thc hnh ha phn tchnh tnh

5.1. Ra dng c

Khi tin hnh th nghim, dng c th nghim phi hon ton sch. kim tra xem dng c sch hay cha, ta c th trng bng mt tnc ct. Nu trn thnh thy tinh ch li mt lp nc mng v u thcoi nh dng c sch. Nu nc dnh trn thnh dng c thnh tnggit th dng c cha sch cn phi ra li.

C nhiu phng php ra dng c: ra bng phng php c hc vra bng phng php ha hc.

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Thng thng ra bng cch dng chi lng c st vo thnh dng c ngm nc hoc dung mi thch hp, sau trng ra nhiu ln. i vicc dng c thu tinh ch nn xoay chi lng nh nhng vo thnh dng c,khng chc mnh s lm v hoc thng y dng c.

i vi cc dng c khng ra sch c bng chi lng v nc th

phi dng cc dung dch ra c tc dng vi cht bn. Vic chn dung dchra da vo cc c im sau:

Bn cht dng c cn ra (l thy tinh, g, st, nha ...) Dng c b bn bi cht g, tnh cht ca n nh th no (c th tan

trong dung mi g, c tnh acid hay base, tnh oxy ha hay kh ...)

Vi cc cht bn l mui v c hoc hu c d tan trong nc th rabng nc x phng. Vi cc cht bn l du m, nha hoc cc cht hu ckhng tan trong nc th c th dng mt s dung mi hu c nh ru,bezen, ether ...

Trong trng hp cht bn bm chc vo thnh dng c th c th bvo bnh mt t giy lc vn, cho dung dch ra vo v lc mnh. Giy vns ko theo cc cht bn i m khng lm xc thnh dng c thy tinh.

Ngoi ra cn c th dng cc dung dch ra c tnh oxy ha kh nh:

Hn hp ra KMnO4 5%: ra s b dng c bng nc, sau ngmdng c vo dung dch KMnO4 5% acid ha bi H2SO4 v un nngnh. Ra sch cc vt mu nu (sn phm phn hy ca KMnO4vcht bn) bng dung dch acid oxalic H2C2O4, hoc cc dung dch khcnh NaHSO3, FeSO4,.... Trng li dng c bng nc ct ri sy kh.

Hn hp ra sulfocromic (gm 20 - 30 g K2Cr2O7 hoc Na2Cr2O7 trong1 lt acid H2SO4 c) c mu nu : dng ra cc dng c bngthy tinh, gm s. Sau khi ra bng dung dch ny, trng li dng cbng nc ct ri sy kh. Hn hp ra sulfocromic c th ti s dngnhiu ln cho n khi mu nu chuyn thnh mu xanh thm miht tc dng ra.

Ch :

Khng hn hp ra ri trn da hoc qun o.

Khi cn ra cc loi ng nh, khng c dng ming ht m phidng qu bp cao su ht dung dch ra hoc c th ngm c dng c vodung dch ra.

5.2. Cch un nng

un nng ha cht, tu theo nhit ta c th s dng cc thit bun nng thch hp. Trong qu trnh un khng nn dng c b thay inhit t ngt v d gy nt v.

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un cht lng:+ Khi un cht lng ng trong bnh cu, cc thy tinh phi lt mt

tm li amian trnh v. Khng c t cc nng nhc t bpxung mt bn m phi lt bng cc vt c tnh cht cch nhitnh g, amian....

+ Khi un cht lng trong ng nghim phi dng cp g cp ngnghim. Trc ht un nh ton b ng nghim, sau mi tptrung un, va un va lc u, hng ming ng nghim v phakhng c ngi.

un cht rn: Dng ng nghim kh, khi un ng nghim nmnghing, u cao hn y mt cht. Lc u un u khp ngnghim, sau mi tp trung un ch c cht rn, hng ming ngnghim v pha khng c ngi.

5.3. LcLc l phng php tch cht rn ra khi cht lng bng cch cho

hn hp i qua mt mng lc.

C nhiu loi mng lc: giy lc, bng thng, bng thy tinh, bngamian, phu y thy tinh xp.... Vic la chn mng lc tu thuc vo bncht dung dch v cht rn cn tch. Nu cht rn hay dung dch lc phhu mng lc loi no th khng dng loi y.

V d: acid hoc kim c s ph hu giy lc cellulose nn khi lcphi dng mng lc amian; CrO3 c tnh oxy ha mnh, t chy cc chthu c th khng dng bng, giy lc thng thng m phi dng bngthy tinh hoc phu lc c mng thy tinh xp.

Tu thuc vo kch thc ca kt ta nh lc m chn loi mng lcc kch thc l rng cho ph hp. Cc loi giy lc, phu thy tinh xp ccc s hiu khc nhau ch kch thc l rng.

V d: vi giy lc, thng phn bit chng da vo mu sc ca bnggiy dn ngoi hp:

Giy lc bng hay bng en: l loi c kch thc l rng ln ( # 10 m). Giy lc bng trng c l rng trung bnh ( # 3 m). Giy lc bng xanh c kch thc l rng nh ( # 1 - 2,5 m).

Nhng kt ta thng thng v dung dch c pH t 0 n 14 thngc lc qua bng hoc giy lc cellulose. Tu theo mc ch lc m ta ccc cch gp giy lc nh sau:

Gp giy lc phng ly phn kt ta, dng cho phu thy tinhthng.

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Gp giy lc c nhiu np gp ly phn dung dch, dng cho phuthy tinh thng.

Ct giy lc trn v phng ly c phn kt ta v dch lc, dngcho phu y phng c l.

Ch : Khi gp giy lc khng nn mit tay qu mnh vo giy lc dgy thng giy khi lc.

Lc di p sut thng bng phu thy tinh hnh nn:

Giy lc sau khi gp, t vo phu phi thp hn ming phu t 3-5mm. Giy lc phi t st vo thnh phu v gn tm phu nht, trnhhin tng c khong cch khng kh lm cho vic lc chm. Phi thm tgiy lc bng nc ct trc khi lc.

Khi lc, cung phu cn chm vo thnh cc dng chy lin tc vlc nhanh hn. Rt cn thn dung dch pha trn kt ta xung ht theoa thu tinh xung phu. Sau khi dung dch chy ht th mi a ktta ln phu.

Ch : khng c kt ta v dch lc cao qu 3/4 mp giy lc; ktta khng cao qu 1/2 chiu cao giy lc.

5.4. Ly tm

Khi cn tch kt ta ra khi dung dch, ta dng my ly tm quay tayhay my ly tm in.

Khi dng my ly tm cn theo ng nhng quy tc sau y:a) Dng cc ng c kch thc, hnh dng nh nhau

b) Khng dung dch qu 2/3 ng

c) Mi ng ng dung dch cn ly tm phi c mt ng i trng (ngnc) nng tng ng v t 2 ng i xng qua trc quay.

d) y np my (nu l ly tm in), cho quay chm ri nhanh dn.

e) Khi tt my phi gim tc dn.

Sau khi ly tm, kt ta nm di y ng nghim, phn dung dch trn quy c gi l nc ly tm. Trng hp cn ta ni trn mt nc lytm th cn lc qua mt giy lc nh.

5.5. Ra kt ta

Thng dng ba cch ra kt ta l ra gn, ra ly tm v ra trnphu lc.

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5.5.1. Ra gn

Rt nc ra vo kt ta trong cc, dng a thy tinh khuy u v lng. Gn b phn dung dch trong, ri li thm mt lng nc ra nav lp li ng tc trn nhiu ln.

5.5.2. Ra ly tmTrn ta trong ng nghim vi vi mL nc ct ri em quay ly tm,

gn b nc ly tm. Lp li vi ln cho n khi ta sch.

5.5.3. Ra trn phu lc

Chuyn ton b kt ta ln phu lc, rt nc ra va ngp ta.Ch cho dung dch ra chy ht qua phu lc ri mi rt tip ln khc. Lpli ng tc ny nhiu ln cho n khi kt ta sch.

Ch : vic ra ta nhanh v sch, mi ln rt nc ra ch cn rt

mt lng nh v phi ch cho dung dch trn phu chy xung ht mi choln tip theo.

kim tra vic ra hon thnh cha, ta ly vo mt ng nghimnh vi git nc ra sau khi ra c vi ln v th xem c cn chtcn ra hay khng.

Vic chn nc ra tu thuc vo tan ca kt ta trong cc dung mi.Thng thng trong phng th nghim hay dng nc ct ra. Cc kt tac tan t thay i theo nhit c th dng nc ra nng. Kt ta d tantrong nc th ra bng nc ngm trong hoc cc dung mi hu c.

5.6. Thc hin phn ng

5.6.1. Kt ta

Thng dng phn ng kt ta tch ring hoc nh tnh cc ion.

Kt ta l tinh th, nu em soi knh hin vi th ta phi c hnhdng xc nh.

Kt ta l v nh hnh hoc keo, nu ngay sau phn ng ta khlng, c m c dung dch.

5.6.2. Soi tinh th

Bng hai cch:

a) Lm phn ng trong ng nghim, dng pipet nh 1 git dung dchc ln tinh th ln phin knh v em soi trn knh hin vi.

b) Lm phn ng trn phin knh: nh 1 git dung dch, thm 1 gitthuc th bn cnh, dng a thu tinh ni lin 2 git phn ng.

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Ch : Dung dch long, tinh th xut hin chm nhng r hnh dng.Nu long qu th h nng phin knh tng nng cht phn ng.

Dung dch c qu, tinh th xut hin nhanh v nhiu, nhng t ctinh th p v hnh dng c trng.

5.6.3. Th xem kt ta hon ton Sau khi quay ly tm, nh t t theo thnh ng nghim 1-2 git thuc

th v quan st. Nu phn nc ly tm khng cn xut hin ta thphn ng kt ta hon ton, nu ngc li l cha hon ton.

Cng th bng cch xem mi trng: nu nc ly tm c pH kim thphn ng ta kim loi nng bng kim hon ton.

5.6.4. Ha tan kt ta

Thm thuc th hay dung mi vo, nu ta khng tan ht th dng

a thy tinh trn k hoc un nng mt cht.Nu mun ha tan ht kt ta, c th phi thm tip thuc th v

dung mi.

Nu mun ha tan ch mt phn ta th em quay ly tm ri gn haydng pipet tch ring ta v dung dch.

5.6.5. Th cht kh

Cht kh thot ra c th nhn bit bng mu, mi hoc dng thuc th.Thuc th c th tm vo giy lc ri dnh vo u pipet, u dy hoc ng

y mt ng nghim khc v nghing hay dc ngc hng kh vo.

5.6.6. Th mu ngn la

Mt s cht khi t trong ngn la khng mu ca n gas th bay hiv cho ngn la c mu c trng.

Cch th: dng dy Nickel-Crom hoc dy Platin ra sch (bngcch nhng vo dung dch HCl c v t vi ln) nhng vo bt thhay dung dch cht th ri a vo ngn la khng mu ca n gas.

5.6.7. Th pH ca mi trng cc phn ng nh tnh trong ng nghim, thng dng cc ch th

mu l nhng cht c mu sc bin i theo pH ca dung dch.

Cch th:

Nh 1-2 git phenolphthalein vo dung dch th. Nu dung dchkhng mu th pH < 8; dung dch c mu th pH > 10; dung dch cmu hng cnh sen th pH = 8-10.

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Nhng giy qu tm vo dung dch th hoc tm t giy qu ri hvo kh bay ra. Nu giy qu c mu th dung dch th hoc khbay ra to dung dch c pH < 6; nu giy qu c mu xanh th pH > 8.

Nh 1 git dung dch th ln giy ch th vn nng ri so snh muvi thang o mu mu (in sn trn hp hoc ba) xc nh gi tr

pH ( cho mi mu mu).5.6.8. iu chnh pH ca mi trng

Khi mi trng ang acid m cn iu chnh v mi trng kim haytrung tnh th thm tng git dung dch KOH, NaOH, NH4OH,NaCH3COO, Na2CO3 hay mui ca acid yu v kim mnh khc hocl dung dch m vng kim. Tt nhin, nu ang xc nh Na+ thkhng dng nhng cht cha Na+ iu chnh mi trng.

Khi mi trng ang kim m mun iu chnh v mi trng acidhoc trung tnh th thm dn tng git dung dch HCl, HNO3,

CH3COOH, NH4Cl, NH4NO3 hay cc mui ca acid mnh v base yukhc hoc l dung dch m vng acid.

bi tp (Bi 2)

2.1. Chn mt tr li ng nht:

(nh du vo tr li ng nht)

a. Phng php ha hc trong phn tch nh tnh l phng php

da trn:A. Cc tnh cht vt l ca mu kim nghim

B. o ph hp th nguyn t, phn t

C. Cc phn ng ha hc

D. Soi tinh th di knh hin vi

b. Phn tch t l phng php phn tch nh tnh tin hnh vi:

A. Dung dch

B. Cht rnC. Dung dch bng ng li kh

D. C dung dch v cht rn

c. Phn tch ring bit l phn tch:

A. Xc nh mt ion bng phn ng c trng

B. Xc nh mt ion bng thuc th c hiu

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C. Xc nh ion bng thuc th nhm

D. Xc nh mt nhm ion bng thuc th c hiu

d. Phn tch h thng l phng php:

A. Xc nh ion trong hn hp nhiu ion bng thuc th c hiu

B. Xc nh cc ion theo th t nht nhC. Xc nh ion bng thuc th nhm

D. Xc nh ion bng phn ng xc nh

2.2. Phn bit ng (), sai (S)

(nh du vo thch hp) S

a. Phn ng tch l phn ng kha 1 ion cn tr

b. Phn ng chia cc ion thnh tng nhm nhhoc tch ring 1 ion gi l phn ng tch

c. Phn ng xc nh l phn ng tm 1 ion clp hoc cn trong hn hp vi cc ion khc

d. nhy tuyt i l gii hn nng cn cpht hin bng mt phn ng

e. Lng cht nh nht tnh bng mcg trong mt mukim nghim cn c pht hin bng mt phnng gi l nhy tuyt i

f. nhy tng i l nng nh nht tnh theog/mL cn c pht hin bi mt phn ng

g. nhy ca mt phn ng xc nh ph thuciu kin tin hnh

2.3. ng li phn tch h thng cc cation theo phng php acid-base da trn nguyn tc no?

2.4. K ra cc thuc th nhm v tn cc cation trong nhm phn tchtheo phng php acid-base

2.5. V s phn tch tng qut 6 nhm cation theo phng phpacid-base

2.6. K tn cc thuc th nhm anion v c tn cc anion theo mithuc th tng ng

2.7. Phn ng gia thuc th nhm anion v anion trong nhm thucnhng loi phn ng no v cho nhng sn phm g ? Nhn bitcc sn phm y nh th no?

2.8. Phn chia cc anion thnh 2 nhm (theo gio trnh ny) l datrn ng li phn tch h thng? Na h thng? Hay phn tchtrc tip? Gii thch.

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Bi 3

cation nhm I: Ag+, Pb2+, Hg22+

Mc tiu

1. Trnh by v gii thch c phn ng ca thuc th nhm vi cc cation nhm I.2. Vit c mt s phn ng c trng ca cc cation nhm I.3. Gii thch c cc bc phn tch theo s 1.

1. Tnh cht chung

Cc cation nhm ny c kh nng to kt ta vi hu ht cc acid (trHNO3), nhng ch c HCl 6N th to ta vi nhm ny m khng to tavi cc cation nhm khc. V th, HCl chnh l thuc th tch nhmcation Ag+, Pb2+, Hg2

2+ ra khi cc cation khc.

T cc mui kt ta ny, ngi ta li tch chng ra v nhn bit tngcation nhm I da vo cc phn ng c trng ca chng.

2. Cc phn ng phn tch c trng ca cc cationnhm I

2.1. Vi HCl long

Ag+ + HCl = AgCltrng, v nh hnh + H+

Hg22+ + 2HCl = Hg2Cl2trng, v nh hnh + 2H

+

(Hg2Cl2 cn gi l calomel)

Pb2+

+ 2HCl = PbCl2trng, tinh th + 2H+

AgCl v Hg2Cl2 c tan t ph thuc vo nhit , trong khi tanca mui PbCl2 ph thuc rt nhiu vo nhit ( 20

oC l 11,0g/L v 100oC l 32,0g/L), nn ngi ta c th tch PbCl2 ra khi AgCl v Hg2Cl2bng nc nng.

AgCl v c bit l PbCl2 tan c trong HCl c v cc dung dchmui clorid m c, nht l khi un nng:

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AgCl + 2HCl = H2[AgCl3]

PbCl2 + 2HCl = H2[PbCl4]

Khi pha long cc dung dch ny th thu c kt ta AgCl v PbCl2tr li.

AgCl c kh nng to thnh cc phc cht tan:AgCl + 2NH4OH = [Ag(NH3)2]Cl + 2H2O

AgCl + 2KCN = K[Ag(CN)2] + KCl

AgCl + 2Na2S2O3 = Na3[Ag(S2O3)2] + NaCl

Khi acid ha dung dch [Ag(NH3)2]+ th kt ta AgCl xut hin tr li:

[Ag(NH3)2]+ + 2HNO3 = AgCl + 2NH4NO3

Hg2Cl2 ch tan trong HNO3 c hoc dung dch cng thy do Hg22+ b

oxy ha thnh Hg

2+

.Hg2Cl2 tc dng vi NH4OH th to kt ta en, do:

Hg2Cl2 + 2NH4OH = (NH2Hg2)Cl + NH4Cl + 2H2O

(NH2Hg2)Cl = [NH2Hg]Cl trng + Hgo en

2.2. Vi KI hay KBr

Ag+ + I- = AgI vng

Ag+ + Br- = AgBr vng nht

AgI ch tan trong KCN v Na2S2O3, khng tan trong acid v NH4OHc. AgBr khng tan trong cc acid, nhng tan trong NH4OH c, KCN vNa2S2O3.

Hg22+ + 2I- = Hg2I2 vng xanh

Hg2I2 + 2I- = [HgI4]

2- + Hgo

C th nhn bit c s c mt ca Hg22+ nh kt ta mu vng xanh

ca Hg2I2 trn nn vng ca cc ta AgI v PbI2, nhng nng ca Hg22+

phi ln.

Pb2+ + 2I- = PbI2 vng

PbI2 + 2I- = [PbI4]

2-khng mu

Tinh th PbI2 khi un nng s tan v lm lnh s to thnh cc tinhth ng nh mu vng rt p. Nhng phn ng ny cng cn nng caPb2+ tng i ln. Khi nng nh th dng cc thuc th khc nh KIhay K2 CrO4 trong mi trng acid yu hoc trung tnh, hoc Na2S trongmi trng kim.

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2.3. Vi H2SO4 long

Pb2+ + SO42- = PbSO4 tinh th trng

PbSO4 khng tan trong cc acid long, nhng tan trong H2SO4 c,HCl c, NaOH c, CH3COONH4:

PbSO4 + H2SO4 = Pb(HSO4)2PbSO4 + 4HCl = H2[PbCl4] + H2SO4

PbSO4 + 4NaOH = Na2PbO2 + Na2SO4 + 2H2O

PbSO4 + 4CH3COONH4 = (NH4)2[Pb(CH3COO)4] + (NH4)2SO4

Cation Ag+ v Hg22+ ch to c kt ta vi SO4

2- khi nng cachng tng i ln, do tch s tan ca cc mui tng ng khng nh.

2.4. Vi NaOH hay KOH

Ag+ + OH- = AgOH trng

2AgOH = Ag2O en + H2O

Ag2O khng tan trong kim d, d tan trong HNO3, NH4OH v d bnh sng phn hu to thnh Ag.

Hg22+ + 2OH- = Hg2O en + H2O

Hg2O tan c trong HNO3 v CH3COOH c.

Pb2+ + 2OH- = Pb(OH)2 trng

Pb(OH)2 + 2OH-

= PbO22-

+ 2H2ODo d to thnh plumbit nn cc mui ch PbSO4, PbCrO4... u d

tan trong kim d.

2.5. Vi NH4OH

2Ag+ + 2NH4OH = Ag2O + 2NH4+ + H2OAg2O + 4NH4OH = 2[Ag(NH3)2]OH + 3H2O

2Hg2(NO3)2 + 4NH3 + H2O = (NH2Hg2O)NO3 trng +2Hgo en + 3NH4NO3 Pb(NO3)2 + NH4OH = Pb(OH)NO3 + NH4NO3

2.6. Vi Na2CO3 hay K2CO3

2Ag+ + CO32- = Ag2CO3 2Pb2+ + CO32- + 2OH- = Pb2(OH)2CO3 Hg22+ + CO32- = Hg2CO3

Hg2CO3 = HgO + Hg + CO2

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2.7. Vi K2CrO4

2Ag+ + CrO42- = Ag2CrO4 nu

Tu theo mi trng m thu c cc sn phm khc nhau: Mitrng kim th to Ag2O en; mi trng NH3 th to [Ag(NH3)2]

+; mitrng acid yu s to Ag

2Cr

2O

7; mi trng acid mnh s khng c kt ta.

Hg22+ + CrO42- = Hg2CrO4 Pb2+ + CrO42- = PbCrO4 vng

PbCrO4 khng tan trong CH3COOH long v NH4OH, nhng tantrong HNO3 long v NaOH.

2.8. Vi dung dch H2S

Ag+ + S2- = Ag2S enAg2S khng tan trong NH4OH, KCN, Na2S2O3, nh

ng tan trong HNO3long, nng:

3Ag2S + 8H+ + 2NO3

- = 6Ag+ + 2NO + 3S + 4H2O

Hg22+ + H2S = HgS en + Hg0 + 2H+ Pb2+ + H2S = PbS en + 2H+

PbS c tch tan rt nh, nn phn ng ny thng c dng tmPb2+. PbS khng tan trong HCl, H2SO4, nhng tan trong HNO3 long, nnghoc trong HNO3 c:

3PbS + 8HNO3 long = 3Pb2+

+ 6NO3-

+ 2NO + 3S + 4H2O3PbS + 8HNO3 c = 3PbSO4 + 8NO + 4H2O

2.9. Vi Na2S2O3

2Ag+ + S2O32- = Ag2S2O3 trngNu d S2O3

2- th to phc tan:

Ag2S2O3 + 3S2O32- = 2[Ag(S2O3)2]

3-

Khi un nng hoc trong mi trng acid th phc ny khng bn, b

phn hy to Ag2S:2[Ag(S2O3)2]

3- + H2O = Ag2S en + SO4

2- + 2H+ + 3S2O32-

2[Ag(S2O3)2]3-

+ 4H+ = Ag2S en + SO4

2- + 3SO2 + 3S + 2H2O

Hg22+ + 2S2O32- = HgS en + Hgo + S + SO2 + SO42- Pb2+ + S2O32- = PbS2O3 trng

PbS2O3 + 2S2O32- = [Pb(S2O3)3]

4-

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[Pb(S2O3)3]4- + 2H+ = PbS + 2S + 2SO2 + SO4

2- + H2O

2.10. Vi Na2HPO4

3Ag+ + HPO42- = Ag3PO4 vng ti + H+Ag3PO4 tan trong HNO3 v NH4OH:

Ag3PO4 + 6NH4OH = 3[Ag(NH3)2]+ + PO4

3- + 6H2O

3Pb+ + 2HPO42- = Pb3 (PO4)2 trng + 2H+Pb3(PO4)2 khng tan trong CH3COOH, HCl, nhng tan trong HNO3,

NaOH:

Pb3 (PO4)2 + 9OH- = 3HPbO2

- + 2PO43- + 3H2O

Bng 8: Tm tt cc phn ng c trng ca cation nhm I

Cation

Thuc thAg+ Pb2+ Hg2

2+

HCl longAgCl trng, tan trongNH4OH d do to phc[Ag(NH3)2]

+

PbCl2 trng, tan trong ncnng

Hg2Cl2 trng, tc dng viNH4OH to Hg

0 +NH2HgCl

H2SO4 long - PbSO4 trng Hg2SO4 trng

NaOH hayKOH

Ag2O enPb(OH)2 trng, tan trongkim d, to PbO2

2- Hg2O en

NH4OH d to phc [Ag(NH3)2]+ Pb(OH)2 trng [Hg2ONH2]NO3 + Hg

0

K2CO3 hayNa2CO3

Ag2CO3 trng Pb2(OH)2CO3 trngHg2CO3 = HgO + Hg +CO2

K2CrO4 Ag2CrO4 nuPbCrO4 vng tan trongkim d

Hg2CrO4

KI AgI vngPbI2 vng tan trong ncnng

Hg2I2vng xanh , nu dthuc th s to thnh:HgI4

2- + Hg0

H2S Ag2S en PbS en HgSen + Hg0

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3. S phn tch

S 1*: S l thuyt phn tch Cation nhm I: Ag+, Hg22+, Pb2+

Ta T1 (AgCl, Hg2Cl2, PbCl2) ra bngH2O + HCl 2N. un si, ly tm nng

Nc ly tm L1(c cation cc nhm II, III, IV, V)

Nc ly tm L2:

Tm Pb2+Ta T2 (AgCl, Hg2Cl2) + NH4OH c, lc l

Kt ta

Tm Hg22+

Nc ly tm:

Tm Ag+

Dung dch phn tch + HCl 6 N (tng git)Lc k, ly tm, ly kt ta

* S thc hnh tng ng: xem s 1, Phn2. Thc hnh phntch nh tnh

bi tp (bi 3)

3.1. Hy hon thnh cc phng trnh phn ng sau:

1) AgNO3 + NaBr ... +....2) AgNO3 + NH4OH d ... + ...

3) Hg(NO3)2 + KId ... + ....

4) Hg2Cl2 + NH4OH d ... + ...

5) Pb(NO3)2 + K2CrO4 ... + ...

6) Pb(NO3)2 + Na2S ... + ...

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3.2. Hy cn bng v la chn mt phn ng pht hin ion Ag+trong dung dch phn tch:

1) Ag+ + I- AgI

2) AgNO3 + H2SO4 Ag2SO4 + HNO3

3) AgNO3 + NH4OHd [Ag(NH3)2]NO3 + H2O3.3. Hy gii thch v sao c th ha tan PbCl2 t hn hp AgCl, PbCl2,

Hg2Cl2 bng cch un nng?

3.4. Khi dng NH4OH c ha tan hn hp AgCl, PbCl2, Hg2Cl2 thcht no s b tan, v sao ?

3.5. V sao ra ta T1 ( s 1) bng nc li phi thm HCl 2N ?

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Bi 4

cation nhm II: Ca2+, Ba2+

Mc tiu

1. Trnh by v gii thch c phn ng ca thuc th nhm vi cc cation nhm II.2. Vit mt s phn ng c trng ca cc cation nhm II.3. Gii thch c cc bc phn tch theo s 2 ( Bi 5, phn phn tch cation

nhm II).

1. Tnh cht chung

Cc cation Ca2+, Ba2+ d dng to kt ta bn vng vi acid H2SO4long, nn acid ny l thuc th nhm tch cation kim loi kim th rakhi cc cation khc. Tuy nhin, cc kt ta sulfat ny kh tan hoc khngtan trong acid hoc kim, nn cn chuyn chng thnh ta carbonat. Sau ha tan ta carbonat bng CH3COOH ri nhn bit tng cation nhm IInh cc phn ng c trng ca chng.

2. Cc phn ng phn tch c trng ca cation nhm II

2.1. Vi H2SO4 long

Ba2+ + H2SO4 = BaSO4 tinh th trng + 2H+

Sr2+ + H2SO4 = SrSO4 tinh th trng + 2H+

Ca2+ + H2SO4 = CaSO4 trng + 2H+

C th chuyn cc ta sulfat MeSO4 (Me2+ = Ba2+ Sr2+ Ca2+) v dng

ta carbonat bng cch un nng vi dung dch Na2CO3 bo ha nhiu ln:MeSO4 Me

2+ + SO42-

+ CO32-

MeCO3

2.2. Vi Na2CO3 hay K2CO3, (NH4)2CO3:

Na2CO3 + MeCl2 = MeCO3 + 2NaCl

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Cc mui carbonat ny t tan trong nc, nhng tan trong cc acidHCl, HNO3, CH3COOH:

MeCO3 + 2HCl = MeCl2 + H2O + CO2

Do CO32- kt ta c nhiu cation nhm khc, nn khng dng n

tch cc cation kim loi kim th ra khi cc nhm khc.

2.3. Vi K2CrO4

Ba2+ + CrO42- = BaCrO4 tinh th vng

Sr2+ + CrO42- = SrCrO4 tinh th vng

Kt ta xut hin ph thuc nhiu vo pH ca dung dch v lun tnti cn bng:

Cr2O72- + H2O 2CrO4

2- + 2H+

cam Vng

BaCrO4 khng tan trong kim, nn y l c s tch Ba2+ ra khi Pb2+.

2.4. Vi amoni oxalat (NH4)2C2O4

Me2+ + (NH4)2C2O4 = MeC2O4 tinh th trng + 2NH4+

Cc MeC2O4 tan trong HCl, HNO3; ring BaC2O4 v SrC2O4 tan ctrong CH3COOH, cn CaC2O4 khng tan.

2.5. Vi Na2HPO4

Me2+

+ Na2HPO4 = MeHPO4 trng + 2Na+

MeHPO4 tan trong HCl, HNO3 v CH3COOH.

Bng 9: Tm tt cc phn ng c trng ca cation nhm II

CationThuc th

Ba2+ Sr2+ Ca2+

H2SO4 long BaSO4 trng SrSO4 trngCaSO4 trng tan nhiutrong nc

Na2CO3 BaCO3 trng SrCO3 trng CaCO3 trng

K2CrO4- Mi trng trung tnh

- Mi trng acid

BaCrO4 vngBaCrO4 vng

SrCrO4 vng--

--

--

(NH4)2C2O4 BaC2O4 trng SrC2O4 trng CaC2O4 trng

Na2HPO4 BaHPO4 trng SrHPO4 trng CaHPO4 trng

Th mu ngn la Mu vng lc Mu mnh Mu gch

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3. S phn tch

S 2*: S l thuyt phn tch cation nhm II: Ca2+, Ba2+ vnhm III: Al3+, Zn2+ (Xem mc 3, bi 5 tip sau)

bi tp (bi 4)


1) BaCl2 + H2SO4 ... +....

2) Ba(NO3)2 + K2CrO4 ... +....

3) CaCl2 + Na2CO3 ... +....

4) Ca(NO3)2 + (NH4)2C2O4

... +....4.2. Hy gii thch v sao c th dng Na2CO3 bo ha chuyn kt

ta BaSO4, CaSO4 thnh kt ta BaCO3, CaCO3 ?

4.3. Hy gii thch v sao c th dng (NH4)2C2O4 nhn bit s cmt ca ion Ca2+ trong dung dch?

4.4. Hy gii thch v sao c th dng K2CrO4 trong mi trng kim nhn bit s c mt ca ion Ba2+ trong dung dch?

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Bi 5

cation nhm III: Al3+, Zn2+

Mc tiu

1. Trnh by v gii thch c phn ng ca thuc th nhm vi cc cationnhm III.

2. Vit c mt s phn ng c trng ca cc cation nhm III.3. Gii thch c cc bc phn tch theo s 2 (phn phn tch cation nhm III).

1. Tnh cht chungCc cation nhm III u c kh nng to thnh cc mui tan trong

mi trng kim d:

Al3+ + 4OH- = AlO2- + 2H2O

Aluminat

Zn

2+

+ 4OH

-

= ZnO22-

+ 2H2OZincat

V vy thuc th tch cation nhm III ra khi cc nhm khc lNaOH hoc KOH d. Sau nhn bit tng cation nhm III bng cc phnng c trng ca chng.

2. Cc phn ng phn tch c trng ca cation nhm III

2.1. Vi NaOH hay KOH

Al3+ + 3OH- = Al(OH)3 trng v nh hnhAl(OH)3 + OH

- = AlO2- + 2H2O

Mun thu c kt ta Al(OH)3 th dng acid yu:

AlO2- + NH4

+ + H2O = Al(OH)3 + NH3

Zn2+ + 2OH- = Zn(OH)2Zn(OH)2 + 2OH

- = ZnO22- + 2H2O

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Mun thu c kt ta Zn(OH)2 th dng acid yu, nhng khng dngNH4

+ v to thnh phc tan [Zn(NH3)4]2+.

2.2. Vi NH4OH

Al3+ + 3NH4OH = Al(OH)3 + 3NH4+

Zn2+ + 4NH4OH = [Zn(NH3)4]2+ + 4H2O

2.3. Vi Na2CO3 hay K2CO3

2AlCl3 + 3Na2CO3 + 3H2O = 2Al(OH)3+ 6 NaCl + 3CO2

Ring Zn2+ to thnh cc sn phm khc nhau tu theo nng dung dch:

2ZnCl2 + 2Na2CO3 + H2O = Zn2(OH)2CO3 + 4NaCl + CO2

3ZnCl2 + 3Na2CO3 + H2O = Zn3(OH)2(CO3)2 + 6NaCl + CO2

2.4. Vi Na2HPO4

AlCl3 + 2Na2HPO4 = AlPO4 keo trng + 3NaCl + NaH2PO4

3ZnCl2 + 4Na2HPO4 = Zn3(PO4)2 keo trng + 6NaCl + 2NaH2PO4

Cc mui phosphat trn u tan c trong kim v acid v c.

2.5. Vi H2S:

Trong mi trng trung tnh hoc amoniac th Al3+ to thnh Al(OH)3:2NH4OH + H2S = (NH4)2S + 2H2O

2AlCl3 + 3(NH4)2S = Al2S3 + 6NH4Cl

Al2S3 + 6H2O = 2Al(OH)3 + 3H2S

Trong mi trng trung tnh hoc kim yu th Zn2+ to thnh ZnS:Zn2+ + H2S = ZnS trng v nh hnh + 2H

+

ZnS tan trong cc acid v c, nhng khng tan trong CH3COOH v

NaOH.

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Bng 10: Tm tt cc phn ng c trng ca cation nhm III

CationThuc th

Al3+ Zn2+

NaOH d AlO2- ZnO2

2-

Na2CO3 Al(OH)3 keo trng Zn2(OH)2CO3 trng

NH4OH d Al(OH)3 keo trng [Zn(NH3)4]2+tan

Na2HPO4 AlPO4 trng Zn3(PO4)2 trng

H2S trong CH3COOH ZnS trng

(NH4)2S trong mi trng trung

tnh hay kim yuAl(OH)3 keo trng ZnS trng

(NH4)2[Hg(SCN)4]

C mt vt Cu2+, to

kt ta mu tm

C mt vt Co2+, to

kt ta mu lc

Alizarin-S

O

O

OH

OH

SO3Na

Kt ta sn

O

O

O

OH

SO3Na

Al

(1/3 cng thc phc)

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3. S phn tch

S 2*: S l thuyt phn tch Cation nhm II: Ca2+, Ba2+ v nhm III Al3+, Zn3+

Dung dch phn tch + H2SO4 2N (tng git) + C2H5OH.un nh, ly tm

Ta T1 (BaSO4, CaSO4)

Na2CO3 bo ho lc k, un nng, lytm. Lp li 3,4 ln chuyn ht taT1 thnh ta BaCO3, CaCO3

Nc ly tm L1:Al3+, Zn2+ + NaOH 2N d

Dung dch: AlO2-, ZnO2

2-, c cn bt +NH4Cl bo ha + NH4OH c (vi git)

Ta T3: Al (OH)3

Tm Al3+

Nc ly tm L3: [Zn(NH3)4]2+

Tm Zn2+

Ta T3: CaCo3, BaCO3 + CH3COOH 2N( tan ht)

Dung dch: Ca2+, Ba2+ + K2CrO45%

(ti dung dch mu vng)

Ta T2: BaCrO4 muvng (khng tan trong

NaOH 2N)

Tm Ba2+

Nc ly tm L2: Ca2+

Tm Ca2+

* S thc hnh tng ng: xem s 2, Phn 2. Thc hnh phntch nh tnh.

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bi tp (bi 5)


1) AlCl3 + KOHd ... +....

2) Al(NO3)3 + Na2CO3 ... +....

3) ZnSO4 + NH4OHd ... +....

4) ZnCl2 + Na2S ... +....

5.2. Hy gii thch v sao c th dng hn hp NH4Cl bo ha vNH4OH c tch ring AlO2

- v ZnO22- ?

5.3. nhn bit s c mt ca ion Al3+ t

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