Thiết kế bài giảng hóa học 12 nâng cao (tập 2) phần 1

Gidi thich: Do trong kim loai co cac electron tir do, chuyen dgng tir do trong mang tinh the, khi co hieu dien the lap tiic cac electron tu do chuyen dgng thanh dong co huong tao ra don

CAO CU GlAc (Chu bien)

TS CAO C U G I A C (Chu bign) - ThS HO THANH THUY

THIET KE BAI GIANG

NflNQCflO-TilPHfll

NHA XUAT BAN H A NOI

ChiroTig 5

DAI CirONG VE KIM LOAI

Bai 19 KIM LOAI VA HQP KIM

A MUC TIEU BAI HOC

1 Kiln thiPc

HS biit:

• Vi tri cua kim loai trong bang tuan hoan

• Cau tao ciia nguyen ttr Icim loai

• Kliai niem, tinh chat va ung dung cua hop kim

HS hiiu:

• Nhirng tinh chat vat li va tinh chat hoa hpc cua kim loai, hop kim

• Nguyen nhan gay ra tinh chSt vat li chung, tinh khu cua kim loai

2 KT nang

• Ren luyen kT nang: Tu vi tri cua kim loai suy ra cau tao va tinh chSt

• • D§n ra dugc nhiing phan ijng hoa hoc va thi nghiem hoa hoc chung minh cho nhirng tinh chat cua kim loai

• Ren luyen kT nang giai bai tap ve kim loai

3 Tinh cam, thai do

Biet dugc nhiing tinh chat quy gia cua kim loai lam cho HS co y thuc bao ve va

su dung tiet kiem kim loai

B C H U A N B! CUA GV VA HS

• GV: - Bang tuan hoan cac nguyen to hoa hgc

- Chuan bi mgt so thi nghiem minh hoa cho tinh khir ciia kim loai

- Dung cu: Ong nghiem ca nho, ong nho gigt, den c6n,

- Hoa chat: + Cac kim loai: Al, Cu Fe (dinh sit sach)

+ Cac dung djch: axit H2SO4 loang, H2SO4 dac, HNO3, CUSO4

• HS: Xem truac noi dung bai hgc

C TI^N TRiNH DAY - HOC

A - KIM LOAI

Hogt dpng 1

I VI TRI CUA KIM LOAI TRONG BANG T U A N HOAN

GV chieu bang tuan hoan len man hinh

(hoac treo baag tuan hoan co to mau

cac nguyen to len bang) cho HS quan

sat

GV huong dan HS tim ra vi tri ciia kim

loai trong bang:

- Kim loai la cac nguyen to co to mau

vang a trong bang tuan hoan

- Phi kim la cac nguyen to co to mau

tim a trong bang tuan hoan

Yeu cau HS xac dinh vi tri cua kim

loai

GV bo sung: Ngoai each xac dinh a

tren thi kim loai nam a:

- Khoi nguyen to s (trir H, He)

- Mgt so a khoi nguyen to p

- Toan bg khoi nguyen to d, f

GV yeu cau HS nit ra ket luan ve vi tri

ciia kim loai

HS: Quan sat, thao luan cho ket qua:

Vi tri kim loai gom:

- Nhom IA dgn VIA (Nhom IA trir H nhom IIIA tru B) va mgt phan nhom IVA,VA, VIA

- Nhom IB dSn VIIIB

- Hai ho Lantan va Actini

HS thao luan cho ket qua:

- Kim loai chiem da so vi tri trong bang tuan hoan

- Kim loai nam a phia duai ben trai ciia

bang tuan hoan

Hogt dpng cua GV Hogt dpng cua HS

Hogt dpng 2

II TINH C H A T VAT LI

1 Tinh chat vat li chung

GV giai thieu: 0 dieu kien thuang cac

kim loai deu a trang thai ran (trir Hg),

CO tinh deo, dan dien, dan nhiet va co

anh kim

Vay the nao la tinh deo, tinh dan dien,

tinh dan nhiet, anh kim va tai sao kim

loai CO cac tinh chat tren chung ta se

nghien cuu timg tinh chat cu the

HS thao luan nhan xet va cho ket qua:

- Tinh deo ciia vdt lieu la tinh bi bien

dang khi chiu ap luc ben ngoai hoac nhiet tac dung va van giu dugc trang thai bien dang do khi thoi tac dung

- Gidi thich: Kim loai co tinh deo la vi

cac ion duang trong mang tinh the kim loai CO the trugt len nhau de dang ma khong tach ra khoi nhau nha nhiing electron tu do chuyen dgng dinh ket chiing vai nhau

•: Electron tir do

® : Ion duang kim loai

Hogt dpng cua GV

GV bo sung: Kim loai c6 tinh deo Ion

nhat la Ag sau do la Al, Cu

GV bo sung: Kirn loai dan dien tot

nhat la Ag, sau do den Cu, Au, Al,

GV b6 sung: Thuang caic kim loai dan

dien tot cung dan nhiet tot

Tinh ddn diin la tinh chit cua vat lieu

khi gin vao 2 diu vat lieu mgt hieu dien thg thi tao thanh dong chuyen dai co huang cua electron tir cue am sang cue duang

Gidi thich: Do trong kim loai co cac

electron tir do, chuyen dgng tir do trong mang tinh the, khi co hieu dien the lap tiic cac electron tu do chuyen dgng thanh dong co huong tao ra dong dien

- Tinh ddn nhiet la tinh chat cua vat lieu

CO th6 truy6n nang lugng (nhiet) tir vi tri nay den vi tri khac

- Gidi thich: Do kim loai co mat cac

electron tu do trong mang tinh the

Cac electron trong viing nhiet do cao co dgng nang lan, chuyen dgng hon loan va nhanh chong sang viing co nhiet do thap han, truyen nang lugng cho cac ion

duang a viing nay nen nhiet lan truyen

dugc tir viing nay den viing khac trong khdi kim loai

Hogt dpng cua GV Hogt dpng cua HS

GV huang dan HS ket luan vin de:

Nguyen nhan gay ra tinh chat vat li

chung ciia kim loai?

2 Tinh

GV giai thieu: Ngoai cac tinh chat tren

kim loai con co mgt so tinh chat vat U

khac nhu: Tinh cung, khoi lugng

rieng, nhiet do nong chay, nhiet do soi

a) Khdi luang riing

GV cho HS nghien cim SGK va yeu

ciu HS cho biet sir bien doi cac tinh

chit: Tinh cimg, kh6i lugng rieng,

nhiet do nong chay, nhiet do soi

HS thao luan cho ket qua:

Anh kim la anh sang thu dugc khi kim

loai hap thu anh sang trang va phan xa ra anh sang co buac song dac trung cho timg kim loai

Gidi thich: Do cac dam may electron

tu-do trong tinh the kim loai hap thu phan

xa hau het nhirng tia sang nhin thay dugc, do do kim loai co ve sang lap lanh ggi la anh kim

HS nhan xet: Tinh chdt vdt li chung ciia kim logi gdy nen boi su cd mat ciia cdc electron tu do cd mat trong tinh thi kim logi

chat rieng

HS nghe giang

HS nghien cuu SGK va nhan xet Khoi lugng rieng ciia cac kim loai khac nhau ro ret nhu:

- Ll (D = 0,5 gam/cm ) la kim loat nhe nhat

- Os (D = 22,6 gam/cm ) la kim loai nang nhat

Tinh cicng ciia kim loai ciing rat khac

nhau nhu: Cr la kim loai cirng nhat, kim loai ki6m thi rat mem co the dung dao de cat

dpng 3

II TINH C H A T H O A H O C CHUNG CUA KIM LOAI

GV huong dan HS rut ra tinh chat hoa

hgc ca ban ciia kim loai:

- Dac diem cau tao cua nguyen tir kim

loai (so electron hoa tri)

- Du doan xu huang ciia kim loai de

CO dugc cau hinh ben cua khi hiem

- Suy ra tinh chat chung cua kim loai

Hogt

\ Tac dun

GV giai thieu: Kim loai co the tac

dung vai nhieu phi kim a nhiet do cao

Yeu cau HS cho biet san pham, lay vi

du minh hoa

HS thao luan nhan xet cho ket qua sau:

- Kim loai thuang co it electron (l-3e)

a lop ngoai ciing

- Xu huang cho electron de dat dugc cau hinh ben

- Tinh chat chung cua kim loai la tinh khir

M ^ M " " + n e

dpng 4

5 vol phi kim

HS thao luan cho ket qua:

Kim loai tac dung vai phi kim tao thanh muoi (trir oxi)

F/t/w.-2Fe +3C12 ^—> 2FeCl3 2A1 + 302 -^-^ 2AI2O3

Fe + S - ^ ^ FeS

Hogt dpng cda GV Hogt dpng cua HS

Hogt dpng 5

2 Tac dung voi dung dich axit a) Ddi v&i dung djch HCl, H2SO4 hang

GV neu vin At Cac dung dich axit

HCl, H2SO4 loang co tinh oxi hoa

Nhung tai sao chi tac dung dugc vai

cac kim loai dimg truac H trong day

hoat dgng?

San pham phan ung thu dugc la gi?

GV huang dan HS Giai quyet vin dh,

Viet cac phuang trinh hoa hgc minh

hoa

GV bo sung: Cac kim loai da hoa tri

thuang bi oxi hoa len so oxi hoa trung

+2

binh nhu: Fe, Cr Fe —> Fe

b) Ddi v&i, H2SO4 (dgc,ndng), HNO3

GV dat vin dk: Tai sao HNO3, H2SO4

dac lai tac diing dugc vai hau het cac

kim loai (trir Au, Pt) Trong khi axit

HCl, H2SO4 loang khong co dugc tinh

chat nhu vay?

GV huang dan HS giai quyet van de

- S6 oxi hoa cua cac nguyen to trong

phan til- axit ITNO3, H2SO4

HS thao luan de giai quyet van de:

Cac phan tir axit HCl, H2SO4 loang co tinh oxi hoa do ion H trong phan tir axit the hien nen chi tac dung vai cac kim loai CO tinh khir manh han hidro

San pham phan img la muoi va H2 Phuang trinh hoa hgc phan ung:

Zn +HC1 -> ZnCb + H 2 t

Zn + H2S04 ^ ^ ZnS04+ H2T

HS thao luan de giai quyet vin de duai

su huong dan ciia GV:

+ 1 +6-2 +1 +5 -2

- So oxi hoa: H2 SO4, H N O3

Hogt dpng cua GV

- Kha nang oxi hoa cua cac nguyen t6

- San pham ciia phan img

- Viet cac phucmg trinh phan img

minh hoa

GV nhan xet va bo sung:

- Tuy vao dieu kien phan ung ma cho

ra cac san pham khir khac nhau

- Thuang cac kim loai bi oxi hoa len

so oxi hoa cao

- Axit FtN03 va H2SO4 dac, ngugi lam

thu dgng hoa Al, Fe, Cr

nhu: Cu, Ag thi chi co thd la N , S

- San pham ciia su oxi hoa

S la: SO2, S, H2S

N la: NO2, NO, N2O, N2, NH4NO3

- Phuong trinh hoa hgc:

3Cu + 8HNO3 -> 3Cu(N03)2 + 2 N 0 1

+ 4H2O 2Ag + 2H2SO4 '° > Ag2S04 + SO21

+ 2H2O Fe+6HN03dac '° > Fe(N03)3+ 3NO21

+ 3H2O

Hogt dpng 6

3 Tac dung voi dung djch muoi

GV lam thi nghiem: Ngam 1 thanh sat

da (cao sach gi) vao dung dich CUSO4

loang sau 1 thai gian, cho HS quan sat

va yeu cau

HS quan sat va nhan xet

Hogt dpng cda GV

- Quan sat hien tugng

- Giai thich

- Viet phuang trinh hoa hgc minh hoa

GV lam tiep thi nghiem: Cho 1

Na vao dung dich CUSO4 loang

HS quan sat va yeu cau:

- Quan sat hien tugng

mau Cho

- Giai thich bang phuong trinh hoa

hoc

GV yeu ciu HS so sanh 2 thi ng

dh rut ra ket luan

GV khic sau kien thuc:

Dieu kien kim loai tac dung vai

dich mu6i tao ra kim loai mai

hiem

dung

Hogt dpng cua HS

- Hien tugng: dung dich CUSO4 nhat

mau dong thai tren thanh sat co Cu kim loai mau do bam vao thanh sat

- Gidi thich: Fe co tinh khir manh hon

Cu Khir Cu^^ thanh Cu

Nong do CUSO4 giam lam mau xanh nhat dan, dong thai Cu kim loai mau do tao ra bam len thanh sat

- Phuang trinh hoa hgc

Fe + CUSO4 -> FeS04 + Cu

HS quan sat va nhan xet

- Hiin tugng: Thay mau Na tan dan

dong thai c6 khi bay ra va dung dich nhat mau, co ket tua mau xanh nhat xuat hien

- Gidi thich: Ban dau mau Na tac dung

vai nuac lam mau Na tan va co khi 2Na + 2H2O -> 2NaOH + H21 Sau do NaOH trao doi vai CUSO4 tao thanh ket tua Cu(0H)2

CuS04+2NaOH->Cu(OH)2 + Na2S04

Kit ludn: Tuy vao ban chat kim loai ma

san pham tao ra la khac nhau

HS ghi bai

11

Hogt dpng cua GV

- Kim loai co tinh khir manh han kim

loai trong muoi

- Kim loai khong tac dung vai nuac a

nhiet do thuong

- Muoi cua kim loai tao ra phai tan

GV bo sung ngoai cac tinh chit tren thi

kim loai con co cac phan img khac:

- Tdc dung vai oxit kim logi: Vi du Al

tac dung dugc vai Fe203, Fe304, CuO

- Tdc dung vdi oxit phi kim Vi du: Mg

CO the khu dugc CO2, SO2

- Kim logi Al, Zn, Be tdc dung vai

dung dich baza

Yeu cau HS viet phuong trinh hoa hgc

4 Tac dung v6"i nu-dc

GV yeu cau HS viet cac kieu phan

img ciia kim loai ma HS da timg biSt?

GV thong bao: Vay nhirng kim loai

nao thi co phan ung theo kilu ciia Na,

theo kieu ciia Fe Co the xet nhu sau:

- Cac kim loai nhom IA, IIA (trir Be,

Mg) CO tinh khir manh tac dung vai

nuac a nhiet do thuong tao ra bazo tan

va hidro

- Cac kim loai co tinh khir yeu han tac

dung vai nuac o nhiet do cao tao ra

oxit kim loai va hidro

HS viet phuang trinh hoa hgc 2Na + 2H2O -> 2NaOH + H21

Fe + H2O — i ^ FeO + H21

HS ghi bai

J

Hogt dpng cda GV

- Cac kim loai co tinh khir rat yeu nhu

Ag, Au, Pt thi khong cac dung dugc

GV chieu len man hinh tranh anh hoac

cac mau vat sau va giai thieu:

- Manh duyra la hgp kim cua Al, Cu,

Mn, Mg

- Thanh thep (1 mieng gang) la hgp

kim ciia Fe, C

- Day chuyen, nhan, bong tai lam

bing vang tay la hgp kim ciia Au, Cu,

Ag

Yeu ciu HS cho biit: Thanh phan ciia

cac hgp kim tren c6 gi giong va khac

nhau

/

Tir do neu khai niem hgp kim

GV bo sung:

- Hgp kim khong phai la hon hgp

thong thuang thu dugc khi trgn 2 chit

vol nhau Ma la san phim thu dugc khi

nung chay hon hgp kim loai vai kim

.loai hay kim loai vai phi kim

- Hap kim c6 ciu tao tinh the va dugc

chia lam cac loai:

HS quan sat thao luan va nhan xet:

Gidng nhau: Deu co thanh phan la kim

loai

Khdc nhau: Ngoai kim loai do con c6

kim loai khac hay phi kim trong hgp kim

Dinh nghia:

Hgp kim la vat lieu kim loai c6 chira mgt

kim loai ca ban va mgt so kim loai va phi kim khac

13

Hogt dpng cda GV

+ Tinh the hon hgp

+ Tinh the dung dich ran

+ Tinh the hgp chat hoa hgc

Hogt dpng cda HS

GV giai thieu:

- Tinh chdt hod hoc cua hgp kim thi

thuang CO tinh chat ciia cac don chat

cau tao nen hgp kim

Vi du: Hgp kim Cu-Zn thi co tinh chat

cua Cu va tinh chat cua Zn

- Tinh chdt vdt li: Co nhiSu thay doi

so vai tinh chat cua cac dan chat

GV neu cac vi du sau ve don chat va

hgp chat

- Vang 99,99% dep nhung mem,

nhirng d6 diing bing vang 99,99% de

meo va mon De khac phuc nhung

nhugc di§m do nguai ta diing hgp kim

ciia vang vai Ag, Cu de lam do trang

sire va due tien

- Do dan dien cua Cu rit tot (dung thu

2, sau Ag) Do dan dien ciia dong giam

nhanh n8u co lan tap chat Do vay, day

dien la d6ng c6 do tinh khiet den

99,99%

- Nhiet do nong chay ciia Sn (232 C)

Nhiet do nong chay ciia Pb (327,4 C)

-> Nhiet do nong chay cua hgp kim

Sn-Pb (thiec han) la 2 l o V

Hogt dpng 9

II TINH C H A T C U A H O P KIM

HS nghe giang va ghi bai

HS thao luan va nhan xet

- Tinh cimg: Hgp kim thuang cung han

cac kim loai thanh phan

- Do ddn dien ciia hgp kim giam nhieu

so vai kim loai don chat

- Nhiet dp ndng chay cua hgp kim giam

so vai kim loai dan chat

Hogt dpng cua GV

Yeu cau HS nhan xet sir biln d6i tinh

chat vat li ciia hgp kim

Hogt dpng cda HS

Hogt dpng 10

III inVG DUNG CUA HOP KIM

GV Chieu len man hinh tranh, hinh

anh bang powerpoint giai thieu ve

nhung ling dung cua hgp kim

HS ghi bai

- Thep khong gi (thep inox): Fe(74%)-Ni(8%)-Cr(18%): Chd tao dung cu y te, nha bep

- Thep Mn rat ben, chiu dugc va dap manh, dung de che tao duong ray xe lira, may nghien da

- Thep W-Mo-Cr rit cung dii a nhiet

do cao, diing ch8 tao luai dao cat ggt kim loai cho may tien, may phay

- Duyra hgp kim Al(95%), Cu(4%), Mn-Mg-Si(l%) Duyra nhe gin nhu nhom nhung lai rit cung, cimg gap 4 lan nhom tuc gin bing thep ma lai nhe bang 1/3 thep Duyra b6n Diing lam vat lieu ch6 tao may bay, 6 to

Hogt dpng 11

CUNG CO BAI VA BAI TAP VE NHA

GV chidu cac bai tap sau len man hinh

cho HS thao luan cung c6 ngi dung bai

hgc:

Cau 1 Kim loai nao trong cac kim

loai sau tac dung dugc vai ca 4 dung

dich muoi: Zn(N03)2, AgN03, CuCb,

AICI3?

HS quan sat theo luan cho ket qua

Cau 1 Chgn dap an D

15

Hogt dpng cda GV

A Fe B Al

C Cu D Mg

Cau 2 Dot chay hoan toan 4,04 gam

hon hgp bot ba kim loai Cu, Al, Fe thu

dugc 5,96 gam hon hgp 3 oxit DS hoa

tan het hon hgp ba oxit nay can V lit

dung dich HCl IM Gia tri ciia V la

iCho 0=16 Al=27, Fe=56, Cu=64)

A 0,12 lit B 0,14 lit

C O , Hit D.O, 24 lit

Cau 3 Nhom chat nao sau day deu tac

dung dugc vai dung dich NaOH?

Bai tap ve nha: 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10, 11, 12 (SGK)

D HU'ONG D A N G I A I BAI TAP TRONG SGK

1 Chgn dap an B

2 Chgn dap an C

3 Chgn dap an C

4 Dung

5 Vi tri ciia kim loai trong bang tuan hoan:

- Cac nguyen to s (nhom IA, IIA)

- Cac nguyen t6 d (nhom IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, IIB)

- Cac nguyen to f (hg lantan va hg actini)

- Mot phin cac nguyen to p

Vl tri kim loai co tinh khir manh nhat: Goc trai phia duoi bang, do la nguyen t6 Cs

Vi tri phi kim co tinh oxi hoa manh nhit: Goc phai phia tren bang, do la

nguyen td F

Cau hinh electron nguyen tir: Cs: [Xe]6s' F: 1 s^2s"2p'

6 Cau hinh electron nguyen tir va ion:

Thidu: N a : l s V 2 p ' 3 s ' Na": l s - 2 s V

Fe: [Ar] 3d'4s- Fe"": [Ar] 3d' Fe'": [Ar] 3d'

7 a) Truang hgp xay ra phan img

Fe + CUSO4 -^

Fe + Pb(N03)2 ^ Vai tro cac chat tham gia phan img

- Chat khir: Fe

- Chit oxi hoa: Cu^", Pb""

b) Phudng trinh hoa hgc dang ion thu ggn:

Fe + Cu^" -> Fe'" + Cu

Fe + Pb^" -^ Fe^" + Pb

8 a) Cu + Fe2(S04)3 ^ CUSO4 + 2FeS04

Cu + 2Fe'" -> Cu"" + 2Fe^"

Fe + CUSO4 -^ Cu + FeS04

Fe + Cu"" -^ Fe-" + Cu b) So sanh: Fe co tinh khir manh han Cu; Fe co tinh oxi hoa manh han Cu" ; Cu c6 tinh oxi hoa manh han Fe"

9 a) Cho dung dich 2 muoi tac diing vai bgt Fe du Phan img xong, Igc bo bgt

Fe du, nuoc lgc la dung djch FeS04

HS viet phuang trinh hoa hgc

b) Ngam hon hgp bgt Cu, Zn, Pb trong dung dich Cu(N03)2 du Sau phan irng, lgc dugc chat ran la Cu

HS viet phuang trinh hoa hgc

2-TKBGHOAH<?C12NC.T2 -| y

10 a) Zn + CUSO4 -^ Cu + ZnS64

Theo phuang trinh hoa hgc cir 1 mol Zn (65g) bi hoa tan thi sinh ra 1 mol Cu

(64 g) bam tren kim loai Zn Do vay kh6i lugng la Zn giam sau phan ung

Ciing suy luan nhu vay ta c6 cac ket qua:

b) va c): Kh6i lugng la Zn tang sau phan img

d) Khoi lugng la Zn giam sau phan irng

11 Phuang trinh ion thu ggn:

M + Pb^" -^ M-" + Pb (1)

M + Cu^" -> M^" + Cu (2) Dat X (g) la kh6i lugng mol ciia kim loai M

n la s6 mol kim loai M tham gia phan ung

a la khdi lugng la kim loai M ban diụ

Theo (1) khi co nx (g) kim loai M tham gia phan irng, sinh ra 207n gam Pb

Ta c6 phuang trinh dai so:

2 0 7 - n x

100% = 19%

a

n ( 2 0 7 - x ) /ộ Rutra: a = - ^ - - - 100 (3) Theo (2) khi c6 nx (g) kim loai M tham gia phan img, sinh ra 64n gam Cụ

Ta CO phuong trinh dai so:

n x - 6 4 -.100% = 9,6%

a Rutra: a = ^ ^ ^ 1 0 0 (4)

9,6 Tir (3) va (4), ta co:

i l ( 2 0 7 ^ 1 0 0 = i ^ ^ ^ ^ ^ l 0 0 ^ x = 1 1 2 ( g )

19 9,6 Kim loai M co khdi lugng mol 112 la cadimi (Cd)

12 Giai tuong tu bai tap 8

Kim loai M co khdi lugng mol 65 g/mol la Zn

E TU- LIEU THAM KHAO

De giai thich cac li tinh ca ban cua kim loai c6 the dua vao thuylt "khi

electron" va thuylt vimg ndng lugng

1 Thuyet "khi electron"

Thuyet "khi electron" cho ring mang tinh the kim loai d thd rin va long bao gom dong thdi cac nguyen tir da bi ion hoa, tire la cac nguyen tir da bi tach mgt phan cac electron hoa tri cua minh Cac electron hoa tri lien kit ylu vdi cac hat nhan nguyen tir, trong do cd mgt s6 chuyin dgng tu do de dang trong toan khdi kim loai, chuyen ddng hdn loan nhu cac phan tir khi Vi thi c6 thi coi nhu cd khi electron chuyin ddng trong mang tinh thi kim loai Kilu lien kit giira "khi

electron" vdi cac nguyen tir va ion kim loai ggi la lien kit kim logi

Gidi thich: Bang thuyet "khi electron" cd thi giai thich dinh tinh cac tinh chit li

hgc dac trung cua kim loai:

• Kim loai cd anh kim vi "khi electron" trong ciu triic tinh thi kim loai tao ra cho kim loai kha nang phan chieu manh cac biic xa nhin thiy Mgt sd kim loai cd mau vi chi hap thu mdt sd birc xa va phan chilu mdt sd biic xa nhin thay khac Ddng cd mau do vi nd da hap thu cac biic xa ciing mau xanh

• Kim loai dan dien tdt vi "khi electron"chuyln ddng tir hon loan sang cd hudng khi lap mdt hieu dien thi d hai diu day din Dun ndng, do dan dien giam vi tang su chuyen dgng hdn loan ciia "khi electron" va tang sir dao ddng cua nguyen tir hay ion kim loai lam can sir chuyin ddng cd hudng cua electron

• Kim loai dan nhiet tdt vi khi tang nhiet do d mdt cho thi d dd nguyen tir va ion kim loai dao ddng manh, truyen sang cac electron tu do, rdi tir cac electron tu do truyen sang cac nguyen tir va cac ion kim loai lan can Cir the dao ddng ciia cac nguyen tir va cac ion trong toan khdi kim loai dugc tang cudng va trang thai nhiet cua khdi kim loai dugc thang bing nhanh chdng

• Kim loai cd tinh deo la nhd "khi electron" lien kit cac tieu phan (nguyen tir va ion kim loai) trong tinh the va chiing cd thi bi xe dich do chiu tac dung cua mdt lire ca hgc

Han che cua thuyet "khi electron" la khdng thi giai thich dugc mdt each triet

de mire do khac nhau ve 4 tinh chat li hgc dac trung cua kim loai va khdng thi giai thich dugc cac tinh chat li hgc rieng cua mdi kim loai

19

2 Thuyet vung nang luotig

Thuyet viing nang lugng dua tren co sd phuong phap obitan phan tir (MO), la thuylt hien dai cd thi khic phuc nhirng thilu sdt cua thuyet "khi electron" ve cau true kim loai

Theo thuylt nay, kim loai rin hay ldng cd -cau true tinh the, nut mang la ion duang Cac obitan nguyen tir (AO) hoa tri ciia cac kim loai dugc td hgp thanh cac MO chung cho toan bg tinh thi Trong sir hinh thanh phan tir hai nguyen

tu sir xen phii giira 2 AO lien kit lam xuit hien 2 MO Khi mdt nguyen tir thu

ba dugc kit hgp vao phan tir nay thi cd sir hinh thanh 3 MO Nhu vay neu tinh thi kim loai gdm N nguyen tir (N = 6.023.10^'^) thi sir xen phu ciia N AO se cho ta N (MO) Moi MO img vdi mdt trang thm nang lugng xac dinh Vi so N rit ldn nen N trang thai xich lai gin nhau tao nen viing nang lugng Su khac nhau vl nang lugng ciia cac trang thai trong gidi han mdt vimg la vd ciing nhd

be chi bing khoang 10"^^ eV, nen cd thi coi viing nang lugng nhu mdt vach nang lugng lien tuc Cac MO ciia vimg nang lugng tuong tu nhu cac MO bat dinh xir khap tinh the kim loai

Hinh 5.1 cho thiy sa dd hinh thanh cac mire nang lugng (tao ra viing nang lugng khi tang sd nguyen tir tuang tac)

E

1 2 4 8 IG N

Hinh 5.1 Sa 66 hinh thanh cac viing nang lugng khi tang lien tuc

so nguyen tu trong tinh the kinn loai

Su diln cac electron vao cac MO trong viing nang lugng xay ra theo thii tu nang lugng tang din va theo nguyen li Pauli (mdi MO tdi da 2e cd spin ddi song) Vay nlu tinh thi gom N nguyen tir, cac vimg nang lugng hinh thanh do sir xen phii cac AO s, p, d, f se chiia toi da 2N (viing s), 6N (viing p), 1 ON (vimg d) va 14N (vimg f) electron Tuy thudc vao ciu hinh electron cua nguyen tir va tinh ddi ximg ciia mang tinh thi, viing chiia electron dam bao cho sir lien

kit goi la viing hod tri (vimg chiia electron hoa tri) va viing trdng tren viing hoa

tri ggi la viing ddn Neu viing hoa tri va viing dan khdng xen phu nhau thi cd mdt khoang gian doan ve nang lugng ggi la vimg cdm 0 cac tinh the kim loai

thudng xay ra sir xen phu nhau ciia viing hoa tri va viing dan Trong chit ban dan viing cam cd chilu rgng AE = 0,1 - 3,0 eV va trong chit dien mdi (each dien) cd A E > 3,0 eV (xem hinh 5.2)

Hoac Vung

v'ung dan

Vung cam re

Vung hoa tri

ng

Vung dan

Viing cam hep

Vung hoa tri

Vat ban dan Vat each dien

Hinh 5.2

Cac electron hoa tri chuyen ddng tren cac MO chung cho toan bd tinh thi nen

cd tac dung rang budc cac ion duong kim loai thanh mdt khdi

Gidi thich tinh chdt vdi li cua kim logi:

• Theo thuyet viing nang lugng, vi cac electron hoa tri chuyen ddng tren eac

MO ciia viing hoa tri tao ra nhirng dam may electron da lam tang kha nang phan chieu va giam kha nang hap thu cac buc xa nhin thay ma kim loai cd

anh kim Cung vi cd cac electron hoa tri chuyen ddng tren cac MO chung

ma lam cho toan bd tinh the ludn ludn lien ket vdi ion duong thanh mdt khdi ddu chiu dugc tac dung ciia luc ca hgc ma kim loai cd tinh deo

• Tinh dan dien va dan nhiet tdt ciia kim loai dugc giai thich nhu sau: cac kim loai dan dien tdt nhat thudc nhdm IA va IB Nguyen tir cua cac kim loai nay chi cd 1 electron hoa tri s nen vimg nang lugng cua tinh the kim loai mdi chira 1/2 sd electron tdi da Trong tinh the chira N nguyen tii' thi cd N (AOs) ciia Idp ngoai cimg xen phii tao ra N (MO), lap thanh viing nang lugng gdm

N mire Vi cd N electron hoa trj nen so electron chi chiem N/2 mire (moi mire 2 electron) N/2 mire bi electron chiem tao thanh viing hoa tri N/2 miic

21

con lai dang trdng tao thanh vimg dan Cac miic bi chiem nam gan true tiep vdi cac mire trdng tao co hdi cho cac electron cd the chuyen dich dugc duai tac dung ciia dien trudng Do dd kim loai nhdm IA va IB dan dien tot

Trong tinh the kim loai nhdm IIA va IIB sir xen phu ciia cac AOs ciia N nguyen tir ciing tao ra vimg N mire Do mdi nguyen tir cd 2 electron s nen

\ung nay phai dugc xep 2N electron, nghia la viing hoa tri da dugc dien dii Tuy nhien, cac AOp ben ngoai ciing xen phu nhau thanh cac MO tao ra vimg nang lugng trdng p vdi 3N mire (vimg dan) Hai viing hoa tri s va vimg dan p xen phii nhau tao thanh viing lai hoa sp Cac electron eiing chuyen dich true tiep theo cac mire cua vimg lai hoa sp khi cd tac dung cua dien trudng

Tuang tu vdi cac nguyen td chuyen tiep d (chang ban Cr 3d 4s ) Neu tinh thi gom N nguyen tir thi kit qua cua su xen phii ciia cac AOs ldp ngoai cimg tao ra vimg s gdm N miic va cua AOd ldp sat ngoai ciing tao ra vimg d gdm 5N mire Su xen phii cua 2 viing s va d tao ra vimg lai hoa ds gdm 6N mire Nguyen tir ciia nguyen td chuyen tiep nhu Cr chi cd 6 electron hoa tri nen tinh thi N nguyen tir chi cd 6N electron hoa tri va chi dien vao 6N/2 = 3N mire Viing lai hoa ds cdn 3N miic trdng nen kim loai chuyen tiep dan dien tdt

Cac kim loai dan nhiet tdt nhd kha nang di chuyen tu do ciia cac electron hoa tri trong tinh the va truyen nang lugng tir phan ndng hon sang phan lanh hon Khi dun ndng, dao ddng cua cac nguyen tir tai chd bi dun ndng trd nen manh hon, gay khd khan cho su chuyen ddng cd hudng ciia electron hoa tri

tu do theo chieu ciia dien trudng hay tir phan ndng den phan lanh Do do tinh dan dien va dan nhiet ciia kim loai giam khi nhiet do tang

Thuc nghiem cho thay khoang 1 electron trong sd cac electron hoa tri ciia nguyen tir kim loai gay ra tinh dan dien va dan nhiet, sd electron hoa tri con lai tham gia tao lien ket cdng hoa tri ben giira cac nguyen tir kim loai Do do phan ldn cac kim loai chuyen tiep cd khdi lugng rieng, nhiet do ndng chay, nhiet do sdi va do cimg ldn hon nhieu so vdi cac kim loai khdng chuyen tiep

Bai 20 DAY DIEN HOA CUA KIM LOAI

A MUC TIEU BAI HOC

1 Ki§n thii'c

HS biit:

• Cac khai niem: Cap oxi hoa - khir ciia kim loai, pin dien hoa, suit dien ddng

va the dien cue

• Cau tao cua pin dien hoa, su chuyin dgng cua cac phin tir mang dien khi pin dien hoa hoat ddng

• Cac phan ung hoa hgc xay ra d catot (cue +) va anot (cue - ) ciia pin dien hoa

• The dien cue chuan ciia kim loai

• Day the dien cue chuan cua kim loai va y nghTa cua nd

HS hiiu:

• Cach sir dung day dien hoa de du doan chieu cua phan iing oxi hoa khir

• Cach xac dinh suat dien ddng chuan ciia cap pin dien hoa

• Tinh dugc the dien cue chuan cua mdt sd cap oxi hoa - khir trong pin dien hoa

3 Tinh cam, thai do

Van dung kien thiie da hgc de giai thich co che hoat ddng ciia pin, acquy thudng diing trong cugc sdng hinh thanh tu duy logic cho HS

B C H U A N B! CUA GV VA HS

• GV: - Lap rap mdt sd pin dien hoa Zn - Cu, Pb - Cu, Zn - Pb theo hinh

5.3 SGK

- Mdt sd tranh anh dugc ve trudc

• HS: On lai bai cii va xem trudc bai hgc

23

C TIEN TRINH DAY - HOC

Hogt dpng 1

I KHAI NIEM VE CAP OXI HOA - KHLT CUA KIM LOAI

GV yeu cau HS

- Viet qua trinh nhudng, nhan electron

ciia cac kim loai va ion sau: Cu, Ag, Fe,

Ag", Cu-", Fe-"

- Cho biet vai trd ciia cac chat trong

ban phan irng

GV gidi thieu: Dang oxi hoa va dang

khir ciia cimg mdt nguyen td tao nen

cap oxi hoa-khii' ciia kim loai:

o-~ ,-^ D ' t t s o x i b d a /

Bieu dien: ^ /u,, , ,

/ D ' n g kho Yeu cau HS viet eac cap oxi hoa- khir

cho cac nguyen td kim loai tren

GV bd sung: Ngoai cap tren cdn mdt sd

cap dac biet nhu: ^^ / i, - ^ /i T

HS viet cac cap oxi hoa / khir:

AgV cu^y Fe-y / A g - / C u ' / F e

Hogt dpng 2

II PIN DIEN HOA

1 Khai niem ve pin dien hoa, suat dien dong va the dien circ

GV lam thi nghiem:

- Cdc 1 dung 50ml dung dich CUSO4

IM cdc 2 dung 50ml dung dich ZnS04

IM hai cdc ndi vdi nhau bang dng chu

U cd chira KNO3 liim cau ndi

- Nhiing vao cdc CUSO4 1 la Cu, cdc

ZnS04 1 la Zn hai la kim loai nay dugc

HS quan sat thi nghiem va nhan xet:

Hiin lugng:

- Kim vdn ke bi lech ve phia circ Cu cd

gia tri 1,10V

- Dien cue Zn bi an mdn dan

- Cd 1 ldp kim loai Cu bam len dien circ Cu

- Kim vdn ke bj lech cd nghTa la xuit

hien 1 hieu dien thi giu'a hai dien cue,

chirng td tren mdi cue cd 1 hieu dien

the nhat dinh

- Hieu dien the giua 2 dien cue (Epjn)

dugc ggi la suat dien ddng

E = E - E

Hogt dgng ciia HS

- Mau xanh ciia dung dich CUSO4 bi

nhat dan

2 Ctf che phat sinh dong dien trong pin dien hoa

GV hudng dan HS giai thich ca chi

hoat ddng ciia pin dien hoa Zn-Cu

- Giai thich hien tirgng xay ra tren moi

Do vay dien circ Zn bj mdn dan

- Dien cue ddng: dung dich Cu- bi

khir thanh Cu kim loai

Cu'^ + 2 e ^ C u

Do vay tren cue Cu cd 1 ldp ddng bam vao va dung dich CUSO4 bi nhai mau dan

- Dien cue Zn: Zn -^ Zir' + 2e nen du

electron nen mang dien tich am (dien cue am)

25

Hogt dpng cua GV Hogt dpng cda HS

- Diin cue Cw:Cu-"+2e->Cu nen

thilu electron mang dien tich duong (dien cue duang)

=> Khi ndi 2 cue vai nhau bdng mot ddy ddn thi lap tuc tgo ra su chuyen electron tic cue Zn sang cue Cu

GV yeu ciu HS kit luan ve ca che hoat

ddng cua pin

GV bd sung:

- Cue Zn la nai xav ra su oxi hoa nen

ggi la cue anot

- Cue Cu la nai xay ra sir khir nen ggi

la circ catot

INUU i;u t;au iiui ^^^^llua u u n g u i v n i-^iiv^j;

trung hoa dien tich Do dd qua trinh chuyin electron dugc thuc hien lien tuc

- Phan ling xay ra trong pin

Zn + Cu^" -^ Zn^^ + Cu Kit lugn:

- Trong qua trinh hoat ddng cua pin co

su bien ddi ve ndng do cae ion Zn , Cu^"

- Ddng dien tao ra la ddng dien mgt chieu

- Suat dien dgng cua pin phu thudc vao: Ban chat kim loai, ndng do dung dich va nhiet do

HS ghi bai

Hogt dpng 3

III THE DIEN ClTC C H U A N CUA KIM LOAI

GV dat van de: Gia tri hieu dien the ciia

chiing ta do dugc trong thi nghiem tren

la hieu ciia cac the dien cue

HS thao luan va nhan xet

- Khdng the do dugc gia tri tuyet ddi ciia the dien cue

GV hudng dan HS giai quylt vin dl

GV chuyen tiep: Dien cue chuan cua

hidro dugc eau tao nhu the nao? Chiing

ta ciing nghien cim trong muc sau

1 Dien cue hidro chuan

Hogt dpng cda HS

- Vi vay ngudi ta dua ra 1 the dien cue

so sanh Chip nhan quy udc the dien cue ciia nd bang 0

- Dien cue dugc chgn la dien cue hidro chuan

GV chieu dien cue chuan hidro len man

hinh eho HS quan sat va yeu cau HS

neu cau tao ciia dien cue chuan hidro

Platin

dd axit

/ / :> ^ > > / / ^

Vay ca che hoat ddng cua dien cue

hidro dien ra nhu the nao?

HS quan sat va nhan xet

- Gdm mdt tam platin cd phii mudi platin nhiing trong dung dich axit H

IM Khi hidro dugc thdi lien tuc dudi

ap suat latm, khi hidro dugc hap phu lien tuc tren be mat tam platin

HS nghien ciiu SGK va nhan xet

H,< >2W + 2e

Vdi the ciia dien cue chap nhan la 0,00V d mgi nhiet do Tire la

2 H * / H , 0,00 V

2 The dien cu-c chuan cua kim loai

GV cho HS nghien ciiu SGK yeu cau

HS cho bilt:

- Cach lip thilt bi xac dinh the dien

cue chuin ciia mdt kim loai nao dd

HS nghien cim SGK va nhan xet

- Thiet bi xac dinh the dien chuin cua kim loai Zn dugc lap nhu hinh ve

27

Hoat donu ciia GV Hogt dgng ciia HS

Vi ciu: Kim loai Zn

Gia tri dien ke cho biet dieu gi?

- Ciic phan irng xay ra trong qua trinh

hoal dgng ciia pin

GV: Tirang tu hay vicl cac qua trinh

xav ra trong pin xac dinh:

- The dien cue chuan ciia kim loai Ag

Zn + 2 H " -^ Zn^" + HT

HS thao luan cho ket qua:

- Do Epin = + 0,80V va dien cue Ag la dien cue duang Dien cue hidro la dien cue am

- Phan img xay ra trong pin dien hoa: Tai cue am (anot):

Hogt dpng cua GV Hogt dpng cua HS

H2 -> 2H" + 2e Tai cue duong (catot):

Ag" + e ->Ag

=> 2Ag" +H2 -^ 2 H " +2Ag Hogt dpng 4

IV DAY THE DIEN CUC C H U A N CUA KIM LOAI

GV cho HS nghien cuu SGK va yeu

cau HS cho biet

- The nao la dien cue chuan ciia kim

loai

- Nguyen tac sap xep eac cap oxi hoa

khu

GV chieu len man hinh day the dien

cue chuan ciia kim loai cho HS quan sat

va bd sung: Cap H /H2 la cap dua vao

de so sanh ngoai ra cdn cd cap

Fe" /Fe" nam giiia cap Cu va Ag

HS nghien ciru SGK va nhan xet

- Thi diin cue chudn: la gia tri cita

dien circ chuan ciia kim loai so vdi dien cue hidro d 25 C, dan vi V(vdn)

- Nguyin lac sdp xip: Gia trj the dien

cue chuan ciia cae kim loai dugc sap xep tir thap den cao thi dugc day the dien cue chuan ciia kim loai

HS ghi bai

Hogt dpng 5

IV Y NGHIA CUA DAY THE DIEN CUC C H U A N CUA KIM LOAI

1 So sanh tinh oxi hoa -

khu-GV chilu lai day the dien cue chuan

ciia kim loai len man hinh eho HS quan

sat va yeu ciu HS cho biet: theo chieu

mui ten thi tinh oxi hoa, tinh khir bien

ddi the nao?

HS quan sat, thao luan va nhan xet

29

Hogt dpng cua GV Hogt dpng cua HS

2 Xac djnh chieu cua phan img oxi hoa - khir

GV yeu cau HS so sanh tinh oxi hoa

ciia ion kim loai, tinh khir ciia kim loai

va the dien cue chuan ciia 2 cap oxi hoa

2+

khir: Cu /Cu, Ag /Ag

GV yeu cau HS neu chieu phan iing tir

do riit ra quy tac phan img cua 2 cap the

dien cue chuan

GV nhan xet va bd sung:

- Quy tac a dimg de xet chieu phan

img ciia cae cap oxi hoa khir

- Neu cd nhieu cap trong cimg mgt mdi

trudng thi hai cap cd the dien cue chuan

khac nhau nhieu nhat thi phan img

trudc

HS thao luan cho ket qua:

- Ion Ag cd tinh oxi hoa manh hon ion Cu^"

- Kim loai Cu ed tinh khir manh hon kim loai Ag

Thi dien cue chuan: E° > E "

Ag'/Ag Cii'"/Cu

=:> Chieu xay ra phan ling giira 2 cap oxi hoa khir

Cu + 2Ag" ^ Cu^" + 2Ag

HS Phan ring xay ra theo quy tac anpha ( a )

Hogt dpng cua GV

GV chieu bai tap sau len man hinh cho

HS thao luan:

Khi cho hdn hgp Mg, Zn vao dung

dich chiia cae mudi Cu(N03)2, AgNOa

Neu thir tu eac phan irng xay ra trong

dung dich

Hogt dpng cua HS

GV nhan xet ket qua HS trinh bay va

yeu cau HS dua vao da thi dien cue

chuan hay cho biet ion H " trong dung

dich cd the oxi hoa dugc nhirng kim

loai nao?

HS quan sat va thao luan cho ket qua Thii tu the dien cue chuan ciia cdc kim loai trong day difn hoa

M g - ' Z r i ' C u ' A j "

Mg Zn Cu Ag (Gia tri the dien cue chuin tang din) Nen Mg tac dung vdi AgNOs trudc

Mg +2Ag" -^ Mg^" +2Ag

- Neu Mg hit thi Cu tac dung vdi AgNOs

Zn +2Ag" ->Zn^" +2Ag Sau dd ed the cd phan iing neu Ag het

Zn + Cu 2+ Zn^" + Cu

- N e u A g het thi Mg tac dung vdd Cu

Mg + Cu^" -> Mg^" + Cu Sau dd cd the cd phan iing neu Mg het

Zn + Cu^" -^ Zn^" + Cu

HS nhan xet: Nhirng kim loai cd the dien cue chuan am thi bi ion H oxi hoa

GV dat vin de: Lam the nao de xac

dinh thi suit dien dgng chuan ciia pin

HS thao luan va nhan xet

Ta cd

(+1 "(-)

31

Hogt dpng ciia GV

dien hoii khi biet the dien cue chuan ciia

cap oxi hoa khu cua dien cure am va

dien civc duang

Tir dd xac dinh suat dien ddng chuan

ciia cap pin Zn-Cu

^ F • =F° - F"

^ "^-pin '^cu='/Cu ^ ?

Zn-' /Zn

= 0,34V-(-0,76V) = 1,1V

4 Xac djnh the dien cue chuan ciia cap oxi hoa - khir

HS thao luan va nhan xet

Ta cd E = E,., - E ,

GV dat van de tiep: Lam the nao de xac

dinh the dien cue chuan ciia cap oxi hoa

khir khi biet suat dien dgng ciia pin dien

hoa vii the dien cue chuan ciia cap oxi

hoa - khu cdn lai

Tir do xac dinh the dien cue chuan ciia

cap Ni- /Ni biet Epjn Ni-CLi= 0,60V va

E" „ , =0,34V

^ p m - t-( + ) (-)

Trudc het phai xet cap oxi hoa khir can xac dinh the ddng vai trd la cue am hay cue duang trong pin Sau dd tir cdng thiic Ep|„ = E,^| -E|_jtinh dugc the dien circ chuan ciia cap oxi hoa - khir can xac dinh

Vi du: Epin Ni-Cu= 0,60V ta thay Ni

hoat ddng han Cu nen Ni ddng vai tro

la circ am, Cu ddng vai trd la cue duang

CUNG CO BAI V A BAI TAP VE N H A

GV chieu eac bai tap sau len man hinh

cho HS thao luan cung cd ndi dung bai

hoc:

HS quan sat theo luan eho kit qua

Hogt dpng cua GV

Bai 1 Biet suit dien ddng chuin ciia

pin Zn-Cu la +1,10 vdn, thi dien cue

chuan ciia dien cue Zn la -0,76 vdn, thi

dien cue chuin cua dien cue Cu la

A + 0,34 vdn B - 0,34 vdn

C.-1,86 vdn D.+1,86 vdn

Bai 2 Trong day thi dien cue chuin

cua kim loai, vi tri mdt sd cap oxi hoa

-khir dugc sip xIp nhu sau: A1^"/A1,

Fe-"/Fe, Ni2"/Ni, Cu'"/Cu, Fe^"/Fe2",

Ag"/Ag, Hg^"/Hg Trong sd eac kim

loai Al, Fe, Ni, Cu, Ag, Hg thi cd bao

nhieu kim loai khi tac dung vdi dung

dich mudi Fe " chi khir duac Fe^" vl

D HU'ONG D A N G I A I BAI TAP TRONG SGK

Phan img hoa hgc

b) Cap Ag"/Ag va Fe "/Fe thi Ag la cue duang cdn Fe la cue am Phan ling hoa hgc Fe + 2Ag'' Fe'" +2Ag

c) Cap Ag"/Ag va Pb'"/Pb thi Pb la cue am cdn Ag la cue duong

Phan irng hoa hoc Pb + 2Ag" -» Pb " + 2Ag

5 Chgn dap an C

7 Trong phan img Fe + Ni ^- Fe + Ni

a) Fe la cue am cdn Ni la cue duong

M " / M (theo quy udc viet dang oxi hoa/dang khu) Hai trudng hgp cd the xay ra:

- Neu thanh kim loai de nhudng electron (M -> M " " + ne), ion M " " tao ra

se dugc phan tan vao dung dich, electron d lai tren thanh kim loai M lam eho thanh kim loai tich dien am va cd mdt dien thi am so vdi dung dich -^ E°„ < 0

- Neu M " trong dung dich de nhan electron ( M " " + ne ^ M ) thi nd se nhan electron ciia thanh kim loai M lam cho thanh kim loai tich dien duong va cd mdt dien the duong so vdi dung dich -> E° „, > 0

Tuong tu nhu vay, ngudi ta cd thi tao ra cae dien cue khi bing each dimg mgt thanh kim loai tra (Pt) hay thanh than chi tilp xuc ddng thdi vdi khf va

nhiing trong dung djch chira ion ciia khi dd Vi du: dien cue hidro H2(k)

(Pt)/H"(dd), dien cue oxi 02(k) (Pt)/OH/dd), dien cue clo Cl2(k) (Pt)/Cr (dd),

Ddi vdi nhung cap oxi hoa khir trong dd khdng cd dan chit, ngudi ta diing dien cue gdm thanh kim loai tra (Pt) hay thanh than ehi nhung trong dung djch chiia dong thdi dang oxi hoa va dang khii-, ching han nhu dien cue Fe^"(dd)/Fe'"(dd) (Pt), dien cue Sn^"(dd)/Sn'"(dd) (Pt),

H, (1dm)"

dd l,On

Lo thoat khi H,

Hinh 5.3 Dien cue hidro tieu chuan

Ngudi ta khdng xac dinh dugc gia tri tuyet ddi cua thi dien cue nhung do dugc hieu dien thi ciia 2 dien cue (suit dien ddng ciia pin) Vi vay, dl so sanh the cua 2 dien cue khac nhau, ngudi ta xac dinh thi ciia dien cue dd so

vdi dien cue hidro chuin, vdi quy udc E°.^ = 0,00V Bing each dd cho

2 r"i / H 2 ^^

phep ta xac dinh dugc the dien cue chuan ciia nhilu cap oxi hoa khir M " " / M

va lap thanh bang tra ciiu (xem bang 5.1) Theo quy udc cua lUPAC, thi dien cue chuan eiia cac cap oxi hoa khir dugc vilt cho qua trinh khir:

Oxh + ne -> Kh Trong dd: Oxh - dang oxi hoa;

Kh - dang khir lien hgp cua mdt cap oxi hoa - khir

35

T h i dien cipc chuan cua mot sd cap oxi hoa/khir

Ca'"/Ca Na"/Na

Mg'"/Mg H2/2H-

Be'"/Be AI^"/AI Ti'"/Ti Mn'"/Mn H2O/OH-

^(V)

-3,04

-2,92 -2,92

-2,90

-2,89

-2,87 -2,71

-2,37

-2,25

-1,85 -1,66 -1,63 -1,18 -0,83 -0,76

-0,74

-0,48 -0,44

Cu'"/ Cu"

SO4'-/ H2SO3 Cu'"/ Cu Fe(CN)^-/ Fe(CN)g^- Cu"/Cu

12/21-MnO^/ MnO^

O2/H2O2 Fe^"/Fe'"

Hgr/2Hg

Ag"/ Ag 2Hg'"/ Hg^^

NO3/HNO2

Pd'"/ Pd HNO2/ NO Br2/2Br- O2/2H2O 2HNO2/ N2O Cl2/2Cr Pb02/ Pb'"

+0,17 +0,34 +0,36 +0,52 +0,54

+0,57

+0,68 +0,77 +0,79

+0,80 +0,92

+0,94

+0,99 + 1,00 +1,06 + 1,23 + 1,29 + 1,36 + 1,45 + 1,50 +1,51

+ 1,69

+1,98

+2,87 1

- Gia tri thi dien cue danh gia kha nang oxi hoa - khir ciia dang oxi hoa va

dang khir: E" cang duang thi dang oxi hoa cang manh va dang khir cang

ylu, ngugc lai, E" cang am thi dang oxi hoa cang yeu va dang khir cang

manh Day la nguyen tac xep day dien hoa kim loai

Vi du: Trong bang nay Li la chit khir manh nhat va F2 la chat oxi hoa

manh nhat

- The dien cue la mdt dai lugng cudng do, khi thay ddi he sd ti lugng ciia

mot nira phan img, gia tri eiia the dien cue chuan EO khdng thay ddi

Vi du: Ag" + e ^ Ag E" = +0,80V

3Ag" + 3e -^ 3Ag E° = +0,80V

- The dien cue cdn phu thudc vao nhiet do va ndng do cua chat oxi hoa va

chat khir theo phucmg trinh Nemst:

a Oxh + ne ^ P Kh

0 303RT [Oxhf

Phuang trinh (5.1) ggi la phuong trinh Nernst eho thi dien cue

Trong do: E - the dien circ d nhiet do T vdi ndng do dang xet

E - the dien cue chuan (25 C, 1M)

n - sd electron trao ddi d dien cue [Oxh] - ndng do mol ciia dang oxi hoa [Kh] - ndng do mol cua dang khir

a - he sd hgp thire cua dang oxi hoa (3 - he sd hgp thiic ciia dang khir

R - h i n g sd khi (8,31451 OJ.K'Vmor')

F - hing so Faraday (96485,309C mol"')

O 25 C cdng thire (5.1) dugc vilt ggn:

Vi du: Xac dinh the dien cue Sn" /Sn va Pb /Pb d 25 C neu ndng do mol

eiia ion Sn va Pb- lan lugt la 1,2M va 0,1M

Bai giai: Tir sd lieu bang tren ta ed:

E° = - 0 ] 4 V - E" = - 0 1 3 V

Ap dung phuang trinh Nemst eho hai trudng hgp tren ta ed:

Dien cue Sn-"/Sn: E = E° + - ^ ^ l g [ S n ' " ] =-0,14V

39