Kỹ thuật giải quyết nhanh gọn đề thi đại học môn Hóa học

Noi khac d i , hoc Hoa khong can phai hoc thuoc long, khong can phai nhcr nhieu nhiJng dieu ma chi can qua suy luan c6 the de dang nhan ra chung chang han trong mot nhom A k h i di tCf

GIAI Q U Y E T

NHA X U A T B A N D A I HOC QUOC GIA H A NOI

THS.NGUYIN DilMH DO

GIAI Q U Y E T NHANH GON

DE THI D A I HOC

mon

THI/ ViEN TJNHBIMH TMUAN

De lam tot bai t h i Dai hoc la mong muon cua tat ca cac em trong cac mua t h i Doi v(5i mon Hoa, day lai la van de bijfc thiet Idn, v i le noi dung de

thi Hoa trai dai ca ba khoi 10; 11; 12 khien klioi lifgrng kien thijfc di/cfng

nhii la ca mot bien trofi menh mong, vo tan

That ra, Hoa hoc la mon hoc rat nhe nhang ne'u cae em biet hoc c6 phqo'ng phap, v i le tat ca phan ufng hoa hoc hay t i n h chat hoa hoc cua cac chat deu dUofc xac dinh thee cac qui luat Do do van de la nam dtfOc cac qui luat nay t h i ta deu c6 the de dang diT doan t i n h chat hoa hoc mot chat, hay

de dang viet ra san pham phan ijfng giffa cac chat ma khong can phai hoc thuoc san pham nhir cac em lam tiio'ng bay lau nay Noi khac d i , hoc Hoa khong can phai hoc thuoc long, khong can phai nhcr nhieu nhiJng dieu ma chi can qua suy luan c6 the de dang nhan ra chung (chang han trong mot

nhom A k h i di tCf tren xuong difdi t h i ban k i n h nguyen tii" cac nguyen to bat

buoc phai tang dan, do'n gian v i so Idp electron cua nguyen tuf cac nguyen to nay tang dan)

Nguyen tSc hoc Hoa la the, tuy vay neu khong c6 ky thuat lam bai t h i trac nghiem khach quan t h i diem so' se khong nhii y so v(5i thiic life Do la thifc te ma bat cuf hoc sinh nao cung c6 the nhan ra, va day chinh la ly do

ra ddi ciia tap sach nay

Chuc cac em t i m thay niem vui trong hoc tap, va nhat la phai dat diftfc ket qua my man nhat trong t h i cuf

Tac gia

Nguyin Dlnh 06

3

O C H L T d N G I

KY THa6T Gl^l DE THI TR^C NGHIEM

Mot dieu khong the phu nhan la du ndm rat chSc cac kien thijTc trong sach giao khoa, nhieu t h i sinh vSn khong the giai quyet tron ven cac cau hoi trong cac de t h i Dai hoc Mot thqc te la da so cac cau trSc nghiem ly thuyet cung nhif bai tap ma t h i sinh xem la rSc roi, d i bi mat diem trong cac de t h i , hoac cac cau ma t h i sinh con mii mcr hay ma ho ve hqdng giai lai c6 the giai quyet rat tot bang phtfang phap loai triT

Vay the nao la phqang phap loai trif? De de h i n h dung, h-ay xem mot v i du sau khong lien quan den Hoa hoc:

Trong so cac nhiem ky long thong My tie xUa den nay, vi tong thong duy nhdt doc than den cud'i dai Id:

A Bill Clinton B Jone F Kennedy

C James Buchanan D Abraham Lincoln

Dap an dung cho cau hoi tren la C (James Buchanan) Nhiftig ro rang, cau

tra Idi nay khong phai xuat phat iii sii hieu biet ve than the James Buchanan,

vi vi tong thong thijf 15 ciia Hop chung quoc Hoa ky nay la mot ten tuoi kha xa

la vdri chung ta Cach lam d day la dung phqang phap loai trif: Trifdc tien loai triT Bill Clinton v i han chiing ta con nh6 hai vg chong tong thong B i l l Clinton

ti/ng CO chuyen ghe tham Viet Nam (nam 2000) Tiep theo, tong thong Jone F

Kennedy cung nam trong danh sach loai trii, vi vu am sat ong vao nam 1963

tai thanh pho' Dallas, tieu bang Texas k h i dang cung phu nhan tham vieng tieu bang nay, la mot sii kien chan dong the gidi thcfi do va hien nay c6 le khong ai khong biet Cuo'i cung, loai trCf not Abraham Lincoln do cupc hon nhan day bait hanh ciia v i tong thong nay da dqcfc ghi lai qua kha nhieu giai thoai

Ro rang James Buchanan phai la sii liia chon cuo'i cung!

Chung ta tiep tuc xem mot v i du c6 le gan gui hon v i du tren, va van la mot

vi du khong lien quan den Hoa hoc:

Hoa iCac Gidp Than hay con c6 ten Hoa uac Patenotre (Pa-ta-not), Id hoa Udc cuo'i Cling nha Nguyen ky vai thuc dan Phap Hoa Uac Gidp Than dugc ky vdo nam ndo ditai day?

A 194S B 1789 C 1752 D 1884

Khong dijng cong thufc doi nam duong lich sang nam am lich, ro rang phai

loai trii nam 1948, v i trieu dai riEa Nguy§n ket thuc k h i vua Bao Dai tuyen bo'

thoai v i , trao an kie'm cho dai dien chinh phu Viet nam dan chii cong hoa vao

nam 1945 Cung nhanh chong loai trii nam 1789, v i day la nam vua Quang

Trung keo quan ra Thang Long tieu diet quan Thanh Luc nay trieu dai nha

5

chtfa diigc

t.hie't lap, v

i ch

i kh

n

Anh mcri

x Lf ng

ngoi vua, la

n hi f

tren, loa

i trC

r nS

m 1752,

g na

m 1802)

Vay liia

chon cuo'i cun

g pha

i l

a D (nam 1884)

Bay gid

,

ta bat ta

Co 3 ancol sau:

do soi cda 3

ancol tren theo chieu

til trdi sang phdi

la:

A (II); (I); (III)

sinh lung tun

cua 2 ancol don

g phan, c

C

k ho ng

the c6

n hi et

do so

i cao

h an

n nhan

h chon

g tim dtfcJc da

gSm AgNOs

vd Cu(N03 )2 Sau

khi cac phan ring

xdy ra hoan toan,

thu dugc dung dich

X gom hai mudi

vd chat rdn Y

gom hai

kim loai Hai muoi

trong X

vd hai kim loai

trong Y Idn lilat Id:

i Fe

t ro ng

X ne

n sa

u

phan ufng khon

triT

ngay C

vi Cu

t ro ng

t ro ng

t ro ng

X Ro

r an g

g trLfcfn g

hgp na

y d

a to

ro

tfu the

t ro ng

giai tra

c nghiem

!

Can biet the

m ran

g phifcfn

g pha

p loai

g mo

t so' ba

giup

ta loai b

m gam

Al bdng dung dich

HNO3 lodng, thu dugc

5,376

lit (dktc) hSn hgp

khi X gom N2,

N2O vd dung dich

chiia 8m gam mudi.

Tl khoi

cua X

so vdi H2 bdng

18 Gia tri cua

-r

Rat nhieu hoc sink nhanh chong xdc dinh dugc buac ddu tien d ddy la phdi tim so mol tilng khi Do Id huang di diing! Theo dU kien dd cho, ta cd so mol

Tuy nhien huang di tiep ddi vdi mot so em cd the Id chua ro rang, khi dd ta dung philang phdp loai triC:

NoO = 0,12.10 + 0,12.8 = 2,16 mol, do do:

(dkc) Mat khdc, khi cho cung lUgng X tren phdn ling vdi mot lUgng dU dung

andehit trong X Id:

A OHC -CH2-CHO vd OHC- CH2-CH2CHO

C CH

s C

- CH

O vd

OHCCH2-CHO

D CH2

=CH-CH0 vd OHC-CHO

truns binh = —

^ = — =

ux •'

nAg =

1 : 3,2 nen phdi loai

t la

d nhCfn

g ca

u l

y thuy

et ha

y b

ai toan m

a

d cr lieu da

cho

la

khon

f t

o r

o la m

ot si

r lii

a cho

n to

et

vi du sau:

X la chat hOu

ca tdc dung vai

Na diC cho so

mol

H2 bay

ra b&ng

so mol NaOH

can diing

de trung hba het

cUng luang

X tren.

Cong thiCc phan tit

r nga

y B v

i CGHMOS khon

g phan tfng di/o

c vcr

i NaO

H2 =

— s

o m

ol Na

o c

6 v

6 so' h6n hop ancol thoa man

de ba

i nen

neu

sa

da

vao gia thie't s

e khong the c6 k

et qua:

Cho hon hap X

gom hai ancol Dot

chdy hodn todn 0,3

mol hSn hap X

thu

dugc 22 gam CO

2 Mat

khdc 0,3 mol X

tdc dung vai Na

dU diiac 5,6 lit

H2 (dkc)

Hai ancol

dd cho Id:

A.

CH3OH vd C2H5OH B.

CH3OH vd C3H6(OH

)2

C.

C2H/OH )2 vd C3HdOH)2 D.

CH3OH vd C3H5(OH

)3

Ta lo

ai tr

if ngay

A, B va

C d

o h6

n hop c6 so

C trun

g binh = so' n

ho

m O

H

trun

g bin

h ^ = 1,66

tren la

C H3 OH

va

C3H5(OH

)3

BA

I T AP A

P D UN

G

1 Ch

o b

ot Mg va Fe vao dun

g dic

h go

m AgN03 va Cu(N03

n toan, th

u difcf

c dung dich

X go

m b

a muo

i va chat ra

m loa

i

Ba muo

i trong

X v

a h

ai ki

m loa

i trong

Y Ia

n li/cf

t la:

A Mg(N03

)2; Fe(N03 )2; Fe(N03

)3 va Fe; Cu

B Cu(N03

)2;

AgNOs; Fe(N03)3

va Ag; Cu

D Mg(N03

)2; Fe(N03 )2; Cu(N03

)2

va Ag; Cu

Gidi

Ro rang dap an can tim Id D That vdy, ta loai trit ngay A, vi Fe vd Cu trong Y phdi tdc dung vai FefNOsJs trong X nen sau phdn ring khong the thu dugc nhQng chat nhii the; tuang tu Id loai trie ngay B vi Cu trong Y phdi tdc dung vai FefNOsJs vd AgNOs trong X, vd cuoi cung loai trit ngay C vi Cu trong

Chu y rdng rdn Y d day Id Ag vd Fe (dang bdi tap cho hdn hap kim loai vdo

CO tinh khit yeu nhdt)

Do do di ddng loai trii cdc phitang dn B, C, D vd lua chon dap dn A

9

X + 2NaOH

> 2CH

4 + K2CO3 +

NagCOg

Chat X

la

A CH2(COOK)2

B CH2(COONa)2

C CH3COO

K D CHgCOON

H a

2 ve

Loai trii D

vi Xphdi chiia nguyen

-Gidi

Chii y rdng vai

dang bdi tap nay,

chi can phdt hicn

mot loai

ta trong

niSi

ddy da cho khong

phdi Id

to nhdn tao thi

ta loai trii ngay.

Vdy di ddng loai

trii

A, B,

C vd chon D.

(ta nilon-6,6;

ta capron;

ta vinilon

Id ta tong hap,

con ta

tdni; len

Id ta thien nhien)

-Gidi

Tuang tu nhu can

6 a tren, ta

loai trii ngay A,

B, C

vd chon

D (ta tdm; ta

nitron; ta nilon-6 khong

c6 nguon goc til

(c) Tron

g ca

c hg

p chat, s

p cha

t crom(III) ch

Trong ca

c pha

t bie

u tren, nhijfn

g pha

t bie

u dun

g la:

A (a), (b) v

a (e) B (a), (c) v

a (e) C (b), (d) v

a (e) D (b), (c) v

a (e

)

(Dai hoc

2013 khoi A)

-Gidi

De y rdng b) Id phdt bieu sai nen loai trie ngay A, C, D (CrO Id oxit baza; CrOs la oxit axit; CrsOs Id oxit liiang tinh) Vay chon B

(4), vinyl axetat (5) Cac chat c6 kha nang tham gia phan uTng trung hcfp tao polime la

A (1), (2) va (3) B (1) (2) va (5) C (1), (3) va (5) D (3), (4) va (5)

Gidi

Vi caprolactam (1) cho dugc phan iXng triing hgp, nhitng isopropylbenzen (2)

khong cho dugc phan iCng triing hgp nen loai trit ngay D, A, B Vay chon C

Cho cac bien phap : (1) tang nhiet do, (2) tang ap suat chung cua he phan

ufng, (3) ha nhiet do, (4) diing them chat xuc tac V2O5, (5) giam nong do SO3, (6) giam ap suat chung cua he phan ufng NhOfng bien phap nao lam can bang tren chuyen dich theo chieu thuan?

A (2), (3), (4), (6) B (1), (2), (4)

C (1), (2), (4), (5) D (2), (3), (5)

Gidi

Chu y rdng chat xuc tdc (4) khong Idm can bdng chuyen dich nen loai trie

ngay A, B, C Vgy chon D

(1) H2NCH2COOH, (2) CH3COOH, (3) CH3CH2NH2 va (4) C2H3COOH

Day xep theo thuf tiT p H tang dan la:

Vi dung dich CH3CH2NH2 c6 moi truang baza nen pH cua dung dich ndy

phdi Ian nhdt trong so 4 dung dich Vgy loai trii A, C

NhiCng dung dich NHoCH^COOH c6 pH xdp xi Id 7, con dung dich CH3COOH phdi CO pH < 7 nen loai trie tiep B Vgy chon D

di/cfc dung dich Y va phan khong tan Z Cho Y tac dung vc;i dung dich NaOH (loang, du) thu d'Jgc ket ttia:

A Fe(0H)3 va Zn(0H)2 B Fe(0H)2 Cu(0H)2 v^ Zn(0H)2

C Fe(0H)3 D Fe(0H)2 Cu(0H)2

11

Gidi

Phdn khong tan Z

Id Cu con du,

do do khong the

tqo muoi Fe^*, tiic

khong the

cd hidroxit liidng tinh

Zn(0H)2, vdy loqi

tril B.

Do do dap dn

g dic h

C US O4

3 ga

m C 1,7

1 ga

m D 0,9

8 ga

m

(Dai hoc

2013 khoi A)

-Gidi

De y

rdng so mol Ba^*

c6 0,01 mol BaSO^,

chua ke con Cu(0H

loqi trii

B, C,

D Vdy chon A

14.

Cho m gam

rSn

X go

m Mg , F

CUCI2.

Sau kh

i pha

n

ufng xon g

m ho

n

hgp ra

n T Bie

t m > m' Va

y ra

n Z

va T Ian Itfot l

C

u v

a MgO

; FeaOg

Gidi

Can luu

y rdng

Mg c6 tinh

khvC mqnh han Fe

nen Mg

se phdn Ung

trUdc vdi

CuCh Chi khi Mg

phdn iZng het, mdi

tdi lugt

Fe phdn ilng Vdy:

Loqi tril

A, do

Mg con thi Fe

chila phdn ling nen

khong the

cd muoi

sdt

trong dung dich Y,

ddn den

T khong the cd

Fe203

Loqi trii B,-do Mg

ud Fe

phdn

iCng het

thi long khoi liiang

magie oxit

va sdt

oxit

tqo thdnh trong T

phdi Ian hon tdng

khdi liicmg Mg

va Fe ban ddu,

tOc m' > m

Loqi trii

C, do

Fe con trong Z

thi CuCl2phdi het, ddn

den T khong the

Mg, Al, Zn

va F

e va

o dun

g dic h

C uC l2

n Y

va dun

g dic

h Z The

t hie

n ke

t tu

a T Nun

g T den khdi li/dn

y ra

n Y gom:

A Zn , Fe , C

u B Mg

, A

l, Zn , Fe , C

u

C Fe , C

u D Zn

, C

u

Gidi

Chu y rdng thii

tii phdn ling cua

cac kim loqi vdi

dung dich CuCl2 Id

Mg >Al>Zn>

Fe

Vdy:

Loqi trie B, vi dung dich Z khi do chi chiia MgCl2, ddn den W chi Id MgO,

khong phai Id hon hap W nhu de yeu cdu

Loai trie A, vi dung dich Z khi do chiia MgClo vd AICI3, ddn den W ciing chi

Loai trCf A, C v i b a n k i n h nguyen ttf F k h o n g t h e I d n hcfn b a n k i n h nguyen

tuT O ( t r o n g m o t chu k i k h i d i tii t r a i sang p h a i , b a n k i n h n g u y e n tuf g i a m dan)

Ttfcfng t i f nhtf t r e n , l o a i trCf D v i b a n k i n h nguyen tijf Si k h o n g t h e \dn hcfn

ban k i n h nguyen tuf A l

Vay chon B

1 7 X la h o n hop gom a x i t cacboxylic dcfn chufc A v a a x i t cacboxylic n h i chufc B

Dot chay h o a n t o a n 0,15 m o l X can viTa du x m o l O2, sau p h a n ufng t h u dtfcfc

i chuf

c B Do

t cha

y

hoan toan 0,25 mo

l X

can visa

du x mol O2 , sa

0 C 0,52

5 D 0,47

5

Gidi

Ta dung bdo todn

oxi de loai tril nhiC sau:

- Loai trie A

vi x = 0,25

vi x = 0,35

-n

, i.^

u

0,475.2 + 0,325-0,35.

- Loai trii C

vi x = 0,525

B chiCa

20 trong phan tii

nen tuang

tU nhu bdi tren

ta phdi

cd:

1 <:

so O trung binh

MO, MCOH)

^ v

a M CO

, (

M l

a

kim loai c

6 ho

a t

ri khon

g doi ) tron

i (dktc ) v

a dun

g dic

h Y chi chi'r

la

A M

g B C

u D Z

n D C

a

(Dai hgc

2013 khoi B)

-Gidi

Vi dung dich Y

chi chiia mot chat

tan duy nhdt nen

H2SO4 dd ddng vita

phdp loai trtt nhii

sau: ^

- Loai trie B

vi M

Id Cu cho ta

he:

80a + 98b + 124c =

24

a H

- b + c = 0,

22,4

- Loai trii C vi M Id Zn cho ta he:

Liiu y: Co the khong can dung da kien so gam hdn hap la 24 gam ud gidi

nhanh nhu sau:

Ggi a, b, c Idn lugt Id so mol MO, MCOH)^ vd M C O , , ta c6 he:

100.39,2 ^

a + b + c = = 0,4

100.98 1,12

= 0,05 22,4

( M + 96)(a + b + c)100

Af = 24 (Mg)

= 39,41

24 + 1 0 0 - 4 4 C

dirge 22,4 l i t k h i CO2 (dkc) M a t khac 0,3 m o l X tac dung \6\a d i i di/gc 5,6

l i t H2 (dkc) H a i ancol da cho la:

A CH3OH; C2H5OH B CH3OH; C3H6(OH)2

C C2H4(OH)2; C3H5(On).3 D CH3OH; C2H4(OH)2

- Loai trie A (c6 so nhom OH trung binh Id 1)

- Loai trie B (c6 so nhom OH trung binh khac so C trung binh)

- Loai trii: C (c6 2 < so C trung binh < 3)

Vdy chgn D

15

m

a chuf

c este) tron

B

C9 H1 4O 4

C

C4 H4 O4

D

C4 H8 O4

Gidi

Can phdi hieu rdng

ancol HOCH=CHOH khong ben

dd chuyen thdnh

andehit glycolic HOCH2CHO Do

dd este

E phdi

cd dang RCOOCH=CHOOCR,

tiic E phdi cd

so C chdn (loai

trit A, B)

Mat khdc vai cong

thicc RCOOCH=CHOOCR thi E

D) Vqy chon C

i ho

a X

bang

CuO tao hcf

i nho

m OH lien ke

a nho

m CH

-Gidi

Trilac het loai trii

A vi

so mol CO2 nhd

han so mol H2O

nen X

Id ancol

no,

khong lam mat mdu

nicac brom

Tiep tuc loqi trii

D vi hidrat hoa

anken duqc ancol dan

chiic no khong cd

khd ndng hoa tan

Cu(0H )2

Cadi ciing loqi trii

C vi

X chdy tqo 0,4

mol CO2 vd

0,5 mol H2O nen

X cd

4C

trong phdn tit Ancol

da chiic

cd 4C trong phdn

ti2 khong the cd

3 nhom -CH3

c ch

o 0,

3 mo

l X tac dun

n ufng Ha

i andehi

t d

a ch

o la:

A HCHO

; CH3CHO

B CH3CHO

; C2H3CHO

C HCHO

; (CH0)2

D HCHO

; CH2(CHO)2

Gidi

,

- "co, 1 C trung cd so hap X rang hon Be y

binh =

^ = = 1,6

6 =

so lien ket n

, ,

"

H

, 0,5 ,

"hh

- Loai tritA (c6 so n trung binh Id 1)

- Loai trie B (c6 2 <so C trung binh < 3)

- Loai trie D (c6 so n trung binh khdc so C trung binh)

Vdy chon C

24 Cho h6n hgp X gom hai axit cacboxyUc Dot chay hoan toan 0,3 mol hon

hgp X, thu di/gc 35,2 gam CO2 Mat khac cho 0,2 mol X tac dung vdi

NaHCOg dtf thu difgc 8,96 l i t CO2 (dkc) Hai axit cacboxylic da cho la:

A CH3COOH; CH2(COOH)2 B CH3COOH; C2H5COOH

C (C00H)2; CH2(COOH)2 D CH2(COOH)2; HOOC-CH=CH-COOH

25 H6n hgp X gom hai axit cacboxylic don chuTc Dot ch^y hoan toan 0,1 mol X

can 0,24 mol O2 thu di/gc CO2 va 0,2 mol H2O Cong thufc hai axit la

Boo toan O cho so mol CO2 =—— ^ = 0,24 mol, vdy loai trie A (do

A gom 2 axit cacboxylic dan chiCc no khi chdy phdi too so mol CO2 = so mol H^)

Vdy chon D

26 Hidro hoa hoan toan 0,05 mol hon hgp X gom hai an debit can 2,24 l i t H2

(dkc) Mat khac, k h i cho cung lifgng X tren phan ufng vdri mot lugng dtf dung

dich AgNOs trong NH3 t h i thu di/gc 17,28 gam Ag Cong thufc cau tao cua

hai andehit trong X la: _

B H - C H O va O H C - C H o - C H O ' ^ ^ '

17

C CH

CHO v

a OHC

-C H2 -C H2

-C

HO

D CHo-CH-CIi

O va OHC

-C H2

nen loai trii B,

Mat khdc

so m.ol.

Ag 0,16 nen

nx :

/i.Ag ^

1 • 3,2

ol h6

n hop

X go

m h

ai andehit c6 kho

i luang

dii

dung dich AgNOa

tron

g NH

3 th

i thu

duqc

8,64 gam

Ag

Cong thufc ca

u ta

o cu

a h

ai andehit trong

X la:

A OKC-CHo-CHO v

a OIIC-CIIO B H-CHO v

a OH

a OH

CH-CI-I

:

nAg =

1 : 3,2 ti

lugng trimg binh cua

hSn hap

- -^^—^

65,6 nen phdi

loai trit

C Vqy chgn D

28 Ii6

n hcf

p X gom h

ai ax

it cacboxyli

c dcf

n chijfc, mac

h hd, k

e tie

p nha

g dang E)o

t cha

y hoa

n Loan 4,0

2 gam X, thu dtfgc 2,3

c 10,0

5 gam X pha

m muo

v

a C3H7COOH

.

D CH3COO

H v

a CallsCOOH

(Dai hoc

2013 khoi B)

-Gidi

Ta

CO so

mol 2 axit trong 10,05 gam

hon hap -

—10,0

2 axit ~

Mat khdc

so mol

2 axit trong 4,02

gam hSn hap =

do do loai trit

C

Vqy chon

B

0,1

29 M la h6n hcfp hai chat hiJu ccf dcfn chijfc X va Y, thanh phan nguyen to' deu

gom C, I I , O (My < My) Cho 0,1 mol h6n hop gom X va Y phan uTng hoan

toan vdi l)icmg du' dung dich AgNOa trong NH3, thu difcfc 38,88 gam Ag

Phan tram khoi \\igng cua X trong h6n hcfp M la

A 83,33% B 66,87% C 75,00% D 90,00%

Gidi

Vdy hdn hap phdi gom HCHO(X) vd RCHO(Y)

Cung phdi loai trit

C, vi neu Y

Id C3H6 thi X

budc phdi

Id HCHO (do so

Id 2, khi do phdi c6

A v

a anke

n B Do

t cha

y ho^

n toan 7,84 U

g thijf

c pha

n tu

f A, B Ian lifgt

6 B

C2 H6

va

C 4H

8

C

C4 H1

0

va

C 4H

8

D

C3 H8

va

C 5H

n h5

n hg

p X gom

th

u duac

0,09 mo

l CO2 Ne

u la

y cun

g m

ot liign

g h6n

di mo

t liign

g dii

dung dic

h AgNO

a tron

n kh

oi \Mng

ke't tu

a thu diigc Id

m her

n 4 gam Con

g X Ian

luat

la:

A CH

^C

-C H3 ,

CH2=

CH-C

=C

H B CH^C-CHa

, CH2

=C=C=CH2

C CH2=

CH

C-2, CH2=

C-C

=CH2 D CH2

=C=CH2, CHs^

CH-C

^C

H

(DQii hoc

2011 khoi A)

-Gidi

Ggi a

la so mol moi chat,

ta c6 2a + 3a + 4a = 0,09

<=> a

= 0,01

Chu y rdng chi

nhUng hidrocacbon c6 noi

ba ddu mach mai

tao ke't tua khi

phdn ling vai dung

dich AgNOs trong NH3.

Vay:

- * Loai frit B-vi mka

tua (max)

= 240.0,01 + 147.0,01

= 3,87 gam <

4 gam

- Loai trii C

vi khong c6 ke't

tua tao thdnh

- Loai tril D

vi mkgt

tua (max)

= 240.0,01 + 159.0,01

- 3,99 gam <

xudt hien tinh hud'ng

cho hSn hgp A

tdc dung vai chat

B, nhdn thdy "sau

mot thai gian luang

ke't tua thu duac

dd vuat qud x

gam" hay

"sau mot thai gian

luang khi thu duac

dd vUat qua y

lit", thi tat cd

cdc chat

33 X l a h o n hcfp g o m 2 ancol no, m a c h h d D o t chay h o a n t o a n X dugc 0,4 m o l

CO2 v a 0,55 m o l H2O Cung lifong X t r e n neu tAc d u n g vdri N a d a dtfac 2,8 l i t

H 2 ( d k c ) X g 6 m

A CH3OH; C2H4(OH)2 B C2H4(OH)2; C3H5(OH)3

C C H 3 O H ; C3H5(OH)3 D C2H5OH; C3H6(OH)2

O CH I/

ON

G

II

KY T HC I^

T DU NG CfiC

D jN H

lUQT

B^

OT O^

N

Tron

g Ho

a hoc, c

6 4 din

h lu

at ba

o to

^n thiforng dug

c sti

r dun

g la:

Di

nh

luat

bao toa

n kh

oi li/cfng

; Din

h lu

at ba

o toan die

n tich;

Dinh iu

at ba

o to

an

electron

va Din

h lu

at ba

o toan nguyen

to

Ta

t nhie

n kh

i d

a sij

f dung cac dinh

luat ba

o

toan t

hi ha

u nh

u khon

g ca

n vie

t ca

c phiiong trinh pha

i ca

c ba

i toan Hoa hoc kh

i d

o s

e nhan

i the

o ca

c eac

h truye

n thon

i toan, th

i sin

h ph

ai bie

t dung din

i toan cho nhanh, gon, hcf

p li, bd

i l

e khon

g nh

at thie

t ba

i toa

n

nao cung sijT dang cac din

h luat, v

a nh

at l

a su

f dun

g dinh luat khon

n ba

i toan tha

y

vi difO

c gia

i do

n gia

n s

e tr

d thanh r

oi ra

m hon!

Nhac l

ai pham v

i SL

f dun

g cii

a ca

c dinh iuat:

1/ Dinh luat bdo

toan khoi lUting

Dinh luat na

f hon hop kim loai hoa

4

; hon hcfp axi

i ancol

; h6

ii di/o

c dun

g kem

21 Dinh luat bdo

toan dien tich

Dinh lu

at na

y a

p dung cho cac ba

i toan lien quan den

so mo

c ba

i toan trong do c6 s

y thay the io

n na

y bang m

n hg

p ca

c ox

it ki

h HCl; H2SO

n bang io

et phan hon hgp cac muo'

i

nitr

at ta

o cun

g sa

n pham la cac ox

it kim loa

i la sg tha

y th

e io

n NO,

at nhie

n ca

n Itf

u y rkn

g s

g thay the nay pha

i "ba

o toan dien tich'', tijf

c

cac io

n dtfcfn

g trong h6n hgp cac catio

n ki

m loa

i ph

ai khon

g thay doi die

n gn

g ho

a hoc

3/ Dinh luat bdo

toan nguyen

to

Dinh lu

at na

y da

c bie

t thic

h hgp v

di ca

c ba

i toan gom nhie

g d

o sa

n pham tao thanh c6 cun

g so' nguyen

tii cu

a mo

t nguye

n to

'

tron

g phan tuf (nhu' ta

o ho

n hg

p NO

; NO

2 ha

y ho

n hg

p Ng

; N2O), hoa

m ta

o ra tua

n the

o mo

t qu

i lua

t xa

c di

nh

vdri s

o

nguyen t>jf cua m o t nguyen to t r o n g p h a n tuf chat p h a n uTng, nhtf h 6 n hop cac axit cacboxylic tac dung v d i lifgng dtf NaHCOa t h i a x i t cacboxyhc don chufc (c6 2 nguyen tuf O t r o n g p h a n ttf) g i a i phong CO2 theo t i le m o l 1 : 1 , con cac a x i t cacboxyhc n h i chufc (c6 4 nguyen tuf O t r o n g p h a n t i l ) g i a i p h o n g CO2 theo t i le mol 1 : 2

D i n h luat nay ap dung dufcfc cho t a t ca c^c b a i t o a n c6 l i e n quan den cac qua

t r i n h oxi hoa khijf nhif toan ve h o n hop cac k i m loai tac dung vdi dung dich chufa h6n hop cac muoi; toan ve h o n hop cac k i m loai tac dung vtJi h o n hop cac p h i

k i m ; toan ve h 5 n hop cac k i m loai tac dung v6i HNO3; v6i H2SO4 dac, nong Dieu can n h d k h i g i a i theo bao t o a n electron l a t a c h i chu y den mufc o x i hoa

ciia cac nguyen to d luc ban ddu va luc ket thuc b a i t o a n ^ k h o n g can quan

tam den mufc oxi hoa cr cac g i a i doan t r u n g gian

Can biet t h e m rSng sii p h a n loai cac ufng dung t r e n c h i c6 t i n h t i i o n g doi, v i mot bai toan H o a hoc c6 the g i a i theo n h i e u each khac n h a u , m 6 i each l a i c6 the v a n dung d i n h luat nay hoac d i n h luat Idiac, t h a m chi v a n d u n g n h i e u d i n h luat cung luc V a n de la each nao cho k e t qua n h a n h chong, va quan t r o n g h o n

ca la each nao giup t a hieu b a i , n a m b a i to't n h a t

Tuy CO 4 d i n h luat bao t o a n , t a hay xet 14 v i du diidi day:

V i d u 1 : Hoa t a n het 16 gam r d n X gom ZnO; MgO; CuO; AI2O3 can vifa du 300 m l

dung dich H2SO4 I M Co can dung d i c h sau p h a n ufng dtioc m g a m h 5 n hop mudi k h a n G i a t r i m la

• Nhdn xet

• K l i o n g dung d i n h luat bao toan electron do bai t o a n k h o n g l i e n quan den

- M i o n g diing d i n h l u a t bao toan nguyen to do k h o n g c6 dau h i e u dac t n / n g

+ D i i n g d i n h luat bao toan d i e n t i c h

Vay mmi,6i = n i k i m loai + n ^ s o :

Vdy chon C

2 3

d u

2: Ch

o m gam

H 2S O4

t k

hi NO The

8 l

it kh

o d

dieu kien tieu chuan Dun

t ca

c

phan iJng de

u xa

y r

a hoa

n toan Gi

0 C 4,0

6 D 3,9

2

(Dai hoc

2013 khoi A)

g nht

f sa

u pha

n ijfng

d mo

l C

u = 0,0325

0,07mol

0,0325mol

Vay 2

a + 0,065 -

0,21 «

a = 0,0725 mol

Do d

o m = 56.0,072

5 = 4,06 gam Va

y cho

n C

a ch

i ca

n liA

i y den muf

c ox

i ho

a

ban dau v

i doa

n trun

g gian

t (dkc ) ho

B y = 6

x + 2,8V

V „

22,4

D y = 8

x + 22,4

+ D i m g d i n h luat bao t o a n nguyen t o N

22 A

+ D i j n g d i n h l u a t bao t o a n electron

Gia sit h 6 n hcfp k h i g o m a m o l N O v a b m o l NO2

De y r a n g hSn h o p k i m l o a i d a cho (3x + 2.2x + 3 x ) = l O x m o l electron, con N"^^ da n h a n (3a + b) m o l electron de tao k h i , t a c6 he:

De y r a n g h o n h o p k i m loai k h i do cung cho ( 3 x + 2.2x + 3 x ) = l O x m o l electron, con N"^^ d a n h a n (3a + 8b) m o l electron de tao k h i , t a c6 he:

2 5

a +

b = 22,4 <!

3a + 8b = lO

x

5 22,4

1

Vay n,„,,^

=4n,, + l0n,„

«>

y ^4^

(^

-IOx) +10^

(10x

Va

y cho

n C

Vi du 4:

Ho

n hcr

p X gom

Zn(N03

)2,

Fe

(N03)3 ,

Th

an

h

phan % kh

di liicfn

g cu

a nitc

f tron

g X la 11,864%

Nung non

g 14,1

6 ga

m X

den kho

i li/cfn

g khong ddi dtfg

c m gam rSn Gia t

ri m !a

A 10,5

6 ga

m B 7,6

8 ga

m C 3,3

6 ga

m D 6,7

2 ga

e dung din

h lu

at ba

o tcan die

n tic

h d

o ra

n th

e io

n NO

^ tron

g muo'

i bkn

g ion

+ C

o th

e dCin

g dinh lu

at ba

o toan electron

do phan uTng nhie

t phan

cac muo'

i

nitr

at l

a ca

c phan

I'rn

g o

xi ho

a khijf

+ Khon

g dung din

h lua

t ba

o toan nguyen

to' d

o khon

g c

6 da

u hie

u da

c triAig

Tuy vay can bie't dinh lu

at ba

o toan nguyen

n kho'

i lu'Ong

9 Gidi

+ Dung din

h lua

t ba

o toan die

n tic

h

De y ran

g JM

^ = 14 t

hi

%N = 11,86

4

Ne

n M =

62 cho % N

O, =

—-

Ch

u y ran

g m gam ran thu du'cfc l

a ca

c ox

it nen:

+ Dijng din

h lua

t ba

o toan electron

, , , 14,16.52,5

=0,1

2 mo

it ki

m loai,

tao

N^^ va O"^ d

a ch

o electro

n ta

o 0° the

o ca

c qu

a trin

h ch

o nhan electron

sau:

V i d u 5: Hoa t a n hoan toan h5n hop gom 2,8 gam Fe va 1,6 gam Cu t r o n g 500 m l

dung dich h o n hop HNO3 0 , 1 M va H C l 0 , 4 M , t h u di/cfc k h i N O ( k h i duy

n h a t ) va dung dich X Cho X vao dung dich AgNOs d\J, t h u diicfc m g a m chat

r a n , B i e t cac p h a n ufng deu xay r a hoan t o a n , N O la san p h a m k h i i duy n h a t

cua N*^ t r o n g cac p h a n ufng G i a t r i cua m la

A 29,24 B 30,05 C 28,70 D 34,10

(Dai hoc ^OlSkhoi B)

• Nhdn xet

Day !a dang toan ve k i m loai (hoac'ion Fe^"^) tac dung vdri d u n g dich hSn hgp

gom H " va N O ^ D a n g nay thUcfng k h o n g ap dung difgc cac d i n h l u a t bao t o a n

nen hau het dtfoc g i a i b a n g each v i e t cac phu'cfng t r i n h p h a n ufng xay r a of dang

ion, sau do so sanh x e m chat hay i o n nao p h a n ufng h e t de d i i n g so m o l ciia no

t r o n g t i n h t o a n

Tuy n h i e n bai toan da cho cf day dac biet c6 the dung d i n h luat bao toan

electron de giai quyet r a t n h a n h gon T h a t vay xet thcfi diem ban dau va liic ket

thiic t h i nghiem, ta t h a y chi c6 Fe va Cu da cho electron de t r d t h a n h Fe'^ va

27

Cac phan ufng xa

y ra theo thu

f tii:

Fe + 4

H^

+ NO:

Fe

3 +

NO + 2H2

^

0,025mol 0,05mo

l 0,05mol

l

Cu'*

: 0,02

5 mo

l

Fe'"

:0,0

5 mo

l

Cr

:0,2 m

ol

Kh

i ch

o X vao dung dich AgNOs

dii, s

e c

6 si

f ta

o than

h 0,

2 mo

Va

y dung dich

X sa

u pha

n ufn

g c

6 chijfa:

3Fe^* + 4

g"

0,0125 m

ol

NO:

> 3Fe^

" + N

O + 2H2O

Fe^" + A

g

0,0125 m

ol

Vay

mkettLia

= mA gc

i + niAg

= 0,2.143,

5 + 0,0125.108

= 30,0

5 gam

+ Cac

h dun

g dinh lu

at ba

o toan electron

CH

O NH

+ 3

e

0,15mol NO: + 4H" + 3e

->

NO + 2H

niAgci

+ mA g

= 0,2.143,

5 + 0,0125.108

- 30,0

5 gam Va

n hoa, thu

hi ch

o X vao dun

i the

o eac

h

thon

g thtfcto

g pha

i la:

3Fe'"

+ 4H

" + NO:

> 3Fe^

" + N

O + 2H2

i the

o ba

o toan electron, chi

i y rkn

g d

o NO, tron

n toan

bo H"

trong t

hi nghie

m d

a pha

e nhan r

a (*

) tii

2 phtfon

g trinh io

n xa

y ra trong bai:

Fe + 4H" + N

O,

3Fe^" + 4H" + NO:

> Fe^

" + N

O + 2H2O

> 3Fe^

" + N

O + 2H2O

Vi du 6: H o n hop X chufa ba a x i t cacboxylic deu d o n chufc, m a c h h d , gom m o t

axit no va h a i a x i t k h o n g no deu c6 m o t l i e n ke't doi (C=C) Cho m g a m X

tac dung viTa du vdi 150 m l dung dich N a O H 2 M , t h u dtfcfc 25,56 g a m h o n

bang dung d i c h N a O H dii, kho'i Itfcfng d u n g d i c h t a n g t h e m 40,08 gam T o n g

khoi lifcfng cua h a i a x i t cacboxylic k h o n g no t r o n g m gam X l a

A 15,36 gam B 9,96 g a m C 18,96 g a m D 12,06 g a m

(Dai hoc 2013-kh6i A)

• Nhdn xet

Khong v a n d u n g di/gc d i n h l u a t bao t o a n nao de r i i t n g d n h o n I d i g i a i b a i

toan, ngoai viec d u n g bao t o a n nguyen to' C va H de suy r a so m o l C O 2 v a H 2 O

thu difoc do dot X t h a y v i v i e t cac p h a n ufng chay

can b a n g Ko; t o a n ve h i d r o x i t \\idng t i n h ; t o a n ve xac d i n h p H cua dung dich;

toan ve cac loai h a t co b a n (p; n ; e) hau n h i i k h o n g sijf d u n g den c a c d i n h

luat bao toan

V i d u 7: Cho m gam h 6 n hcfp X gom a x i t axetic, a x i t fomic va a x i t oxalic tac

dung vdi NaHCOg (dH) t h i t h u dUgrc 15,68 l i t k h i C O 2 (dktc) M a t khac, dot

chay hoan toan cung lifcfng X t r e n can 8,96 l i t k h i O2 (dktc), t h u dtfoc H 2 O

De y rang CO

2 sinh r

a id

hon ho

p X tac dun

ti l

e mo

l 1 : 2 , tuf

va 1 : 2 nen ba

la s

o mo

l CH3COO

H , HCOO

H v

a C2H2O4, ta c6

: a + b + 2c -

0,7

Bao toa

n ox

i cho : 2

a + 2b + 4c + 2.0,4 =

2.0,8 + n„ o 0,6 (mol

2 8,96 22,4

m 33,2

-Vay cho

n A

t ca

c phiion

g trin

h pha n

ufng

xay ra C

O2 :

CH3COOH + 2O

2 —

2HC00H + O

2

2H00C-C00ri + O2

2CO2 2CO2 4CO2

b = 0,2

c = 0,2

Vay m = 60

a + 46b + 90c = 33,2 (gam )

=CH-C00 H ; HOOC-CH=CH-COO

dLfcre

gia tr

n c

o din

h l

a 33,2 Da

Chinh V ] vay viec biet ke't hop dinh luat se cho ket qua nhanh chong hon so

voi chi dung mot dinh luat Day la dieu ma cac hoc sinh can nam k h i giai cac

bai toan Hoa hoc phtiTc tap, chua ke qua do cac em se phat trion kha nang t u

duy hoc Hoa len nhieu Ian

Thong thtfcmg k h i ket hop dinh luat, t h i dinh luat bao toan khoi liTong difoc

dung song song vdi dinh luat bao toan nguyen to' se cho ket qua tot nha't Cung

toan nguyen to Ta se xet them mot so vi du cho viec ket hop dinh luat qua cac

bai toan diTdi day:

Vi d u 8: Nung 4,2 gam h6n hop X gom Fe, Al, Zn, Mg va Cu trong oxi mot thcfi gian

A 0,18 B 0,14 C 0,16 D 0,11

• Nhdn xet

mol S (tijfc so mol ion SO^, ) c6 trong muoi, sau do dung bao toan kho'i Itfong se

tim doge a Cu the l a bao toan S cho

n,, = n , = n „ „ , , - n _ , , = (a - 0,04) mol

S / m u o i S O : /mu(')i M S O j S O , ^ '

+ Cung C O the giai theo bao toan electron do bai toan c6 xay ra cac qua t r i n h

oxi hoa khijf Tuy nhien can lOu y rang khong goi a, b, c, d , e la so mol 5 k i m

loai ban dau, Chi can dai dien 5 kim loai da cho la k i m loai M (voi so' mol la a;

hoa t r i x) de giam hdt an so'

o Giai

+ Dung dinh luat bao toan khoi loong kem dinh luat bao toan nguyen to

Ta C O 4,68 + 98a = 4,2 + 96(a - 0,04) + 64.0,04 + 18a a = 0,11 mol

Vay chpn D

+ Dung dinh luat bao toan electron kem dinh luat bao toan nguyen to'

De y rang k i m loai M cuoi bai da hi oxi hoa toan bo thanh M"""; O2 cuoi bai

bi khCf thanh va S^*^ cudi bai bi khuf thanh

Theo de so mol O2 da phan ufng - ^ 0,015 (m.ol)

Cac qua t r i n h cho, nhan electron:

31

Bao toa

n nguye

n to' S cho:

+ Ke'

t qu

a vin khong do

kem dinh luat ba

h s

o

mol

H2 SO 4

cac

kim loai gia

(4,68-4,2) ,0,896 ,

loai l

a

j,,, = 2nj,„ Cong thijf

phan ufng cu

a

mot kim loai M bat

ki v6i

H 2S O4 dac

nong:

2M + 2nH2S0

4 (dac

) >

M2(S04)

n + nS02 + 2nH2

l, Zn, M

a ta

n hoa

n toa

n Y trong HNO

3 d

a diJO

c

0,896 lit (dkc) ho

h khu

f N*^

So' mo

5 C 0,16

8 D 0,18

0

• Nhdn

xet

Tiiong ti

0,04) + 38.0,04 +

18 « a = 0,19

5 mol

; = = 0,0

la ho

a tri

cua

M

Bao toan electron cho: xa = 4.0,01875 + 3.0,02 + 0,02 = 0,155

Bao toan N cho n^,„^„_ = " N / M f N o , ) , + " N O + " N / N O ,

^ " U N O , = ^ n M ( N O , | „ + " N O + " N 0 3

« " H N O , = ^ n M , N o , „ +nNo + " N O , = + 0,04 = 0,195(mol) Vay chpn B

Bai toan cung c6 the giai rat nhanh nhd dung cong thufc t i n h so' mol HNO3

can dung k h i hoa tan mot hon hcJp cac k i m loai:

2(3,8-3,2)

" H N O , "nNO,/oxilkimloai " n N O, / k i m l M i 16 + 4.0,02 + 2.0,02 = 0,195 mol

V i d u 10: Cho m gam rSn X gom Fe, FeO, Fe203 va Fe304 vao coc difng 100 m l

NO (dkc) la san pham khuf duy nhat va con lai phan r a n la 1,48 gam sat chira tan het Gia t r i m la

+ Dung dinh luat bao toan electron kem dinh luat bao toan nguyen to

Dat cong thijfc trung binh cua ran X la Fe^Oy

Goi a la so mol FoxOy da phan iJng, ta c6 n

t ch

i xa

y r

a 2 qua tn nh khuf N

*^

Gia tri

x l

a

A 0,9

3 B 1,0

5 C 1,1

2 D 0,8

i v

i d

u 9 , d day d

42 (^

—) + 0,25.3

8 + l

^^

- »

a = 0,775 (mol)

Vay X

= 0,77

5 + ^'^^^"^^

= 0,9

3 (mol) Va

Ta C

O ilpg(j^,

o ) =ax mol S

CHO N

a(

3x -2 y) = 0,375+

0,125 = 0,5 fa

x = 0,175

a(56x + 16y) =

10 [a

y = 0,0125

Bao toa

n N cho n„^,„,^^,,^^^

^ =

^^FeiNo,,, +

^ NO +

^^o, =

^ax + 0,25 =

+ Nhac l a i cong thurc g i a i n h a n h t i n h so' m o l Fe(N03)3 t h u dxiac k l i i h o a t a n

hon hcfp g o m sat v a cac o x i t sat t r o n g li/ong d i i HNO3:

+ V i dung d i c h Y c h i chufa m o t chat t a n duy n h a t n e n chat t a n n a y c h i c6

the l a Fe2(S04)3, do do neu goi a l a so m o l HNO3 t h i bao t o a n nguyen to se I a n

\\iat t i n h diJgc so m o l NO ; H2O va Fe2(S04)3 Cuoi cimg d u n g bao t o a n k h o i

lifgng se xac d i n h di/gc a v a c6 k e t qua cAn t i m

+ Co t h e giai theo bao t o a n electron v i c6 x a y r a cac qua t r i n h o x i h o a khuf,

luc nay n h a t t h i e t p h a i dijng k e m bao toan nguyen t o

• QMi

+ DCing d i n h l u a t bao toan kh6"i liforig k e m d i n h l u a t bao t o a n nguven to'

Goi a l a so' m o l HNO3 da dung A p dung d i n h luat bao t o a n cac nguyen to H ,

N, O, t a CO p h a n ufng sau:

(FeS; FeS2) + HNO3 > Fe2(S04)3 + NO + H2O

a a 0,5a

12 Vay 5,2 + 63a = 4 0 0 - ^ + 30a + 18.0,5a <=> a = 0,2

12

Do do V = 22,4.0,2 = 4,48 ( l i t ) Vay chon B

+ D u n g d i n h luat bao t o a n electron k e m d i n h luat bao t o a n nguyen to'

Xem h&n hop da cho gom a mol Fe va b mol S, t a c6 cac qua t r i n h cho nhan electron:

C H O N H A N

3a (3a-H6b)

35

g ba

o toan Fe t

hi phan utng ph

ai ta

o — m

ol Fe2(S04)3

CO

56a + 32b = 5,

2 a-

0,

05

b = 0,0

75

Va

y V = 22,4(^

^-^) = 4,48 h't Va

y chp

n B

• Luu

y

Tach

r ie ng

hon hop d

a ch

o than

h tifti

g dcf

n cha

t rieng le

h ox

i ho

a khijf, da

c bie

t d

o l

a hon hop m

a so' cha

g ba

n ho

n hg

p (Fe

; FeS

; FeS2) c

6 th

e tac

h than

h ho

n hcr

p

gom Fe v

a S

; hon hgp (Fe; Cu

6 th

e tac

h tha

; FeO

; FegOa

; Fe304) c

6 th

e tac

h thanh hon

hgp

gom

Fe va O2 .Dieu

c an liAi y

cho thanh titng

dan chat rieng le

n ha

h lua

t ba

o toa

n electron

C6 the xet

ai toan sau trong de t

hi kho'

i A nam 2013 de r

Hdn hgp

X gom

Na, Ba, Na20 ud

BaO Hoa tan hodn

toan 21,9 gam X

veto

niiac, thu dugc 1,12

lit khi H2 (dktc)

va dung dich Y,

trong do

cd 20,52 gam

Ba(0H)2 Hap thu

hodn todn 6,72 lit

khi CO2 (dktc) udo

Y, thu dugc m

gam ket

tua Gid tri ciia

i the

o eac

h thon

ol 4

chat

tren, ta se difcfc h

e phiion

g trin

h 4 a

n s

o nhiing c

hi c

6 3 phifcfng

trin

g th

e gia

i ra tCtog an Tu

y vay, ne

u bie

t rang b

ai toan c

i tong l

a (

a +

2b) va

(c + d ) t

hi bang k

y nang bie

h c

6 the gia

i ba

i toa

n da cho the

o eac

h tre

n nhif sau:

Goi

a ,

b,

c, d

Ian

B

a v

a BaO

t ro ng

X

Theo de

a c

6 he: <

23a + 62b + 137

c + 153d = 21,

Vay nxaOH = a + 2b = 0,14 mol

Suy ra dung dich sau boa tan ran X c6 chufa 0,12 mol Ba^"^

va (0,14 + 2.0,12) = 0,38 mol OH~ Theo de n^,, = 0,3 mol nen n^^^, = n^^^^ - n ^ , , = 0,38 - 0,3 = 0,08 mol

Ma n = 0,12 mol nen n„ =0,08 mol, ttTc mtettta = 197.0,08 = 15,76 gam

Ro rang each giai kha vat va do phai bien doi toan hoc riTdm ra ma khong phai t h i sinh nao cung c6 the thifc hien difcfc Trong k h i do neu giai bang phiJcfng phap tach rieng hon hgp da cho thanh tCfng dcfn chat rieng le, bai toan chi con 3 an so nhii sau:

Goi a, b, c Ian lifgt la so mol cua Na; Ba va O2 trong X

Chu y Na va Ba da cho electron, con O2 va H"^ da nhan electron, theo de ta c6 he:

a = 0,14

b = 0,12

c = 0,07 22,4

,2+

Do do dung dich Y c6 chijfa (a + 2b) = 0,38 mol O H va b = 0,12 mol Ba'

V i du 13: Cho m gam rSn X gom Cu; Fe; FeO; Fe203 v a Fe304 vao 500ml dung dich HNO3 2M Sau k h i phan ijfng xong diTgc 4,48 l i t NO (dkc) l a san pham khuf duy nhat; dung dich Y v a con 2 gam rSn la Cu chtfa tan bet Cho nifgc

NH3 dii vao dung dich Y Loc lay ket tua sau phan ufng dem nung trong

khong k h i den kho'i lifgng khong doi diigc 16 gam ran Z Gia t r i m l a

A 25,6 B 31,8 C 22,2 D 27,6

• Nhdn xet

Vi Cu con dii nen dung dich Y chufa Cu^^ v a Fe^\t khac do Cu(0H)2 tan

het trong ni/gc NH3 d\i nen 16-gam Z chi l a 0,1 mol Fe203 Nhtf vay c6 the

dimg bao toan khoi liJgng ket hijp bao toan nguyen to cho bai toan

Mat khac do c6 xay r a cac qua t r i n h oxi boa khtJ nen cung c6 the dCing dinh luat bao toan electron ket hgp vdi bao toan nguyen to

37

+ 0,2.3

0 + 18

- +

2 «

m = 27,6 (gam

)

2 2

Vay cho

n D

l C

u v a

F cx Oy

da pha

n ufng , t

a c

6 he

bx = 0,2

by = 0,1

m = 27,6

64a + b(56x +

16y) =

m

2

2a + b(

2x -2 y) -3 0 ,2 = 0,

6

bx = 0,2

2a + 2bx + 0,2 = 0,5.2 =

1

Vay cho

n D

Vi

du 14:

A l

a mo

t triglixerit X

a phon

g ho

a m gam

m liS

n ho

p mud

i khan Do

6 C C55H

]02O6

D C57Hno0

6

• Nhdn xet

c t im difgc con

g thuf

c

phan tuf cu

a A

m triglixeri

t A , ti

Triglixerit A + 3NaO

H

0,01mol 0,03mo

l h6n hop muo'

i + glixerol

0,01mol

Bao toa

n C cho: n„,

^ =n^,^,^

+ nr

-, v

^ ,^

,

C/

A C/

CO , C/

Na ,C () , C/

gh xc ro

l

9 1 34

1 S

Q

' +-

^ + 3.0,01 =

0,53 mo

Bao toan H cho: n„,^ = n^,,„ „ + n„,^,.^_, - n„,,^^„„

= - — — + 0,01.8-0,03.1 = 1,02 mol

18 NhU vay 0,01 mol A c6 0,53 mol C va 1,02 mol H nen phan tijf A c6 53C va 102H

+ Dung dinh luat bao toan nguyen to kem bao toan khoi liTcrng

Dat cong thufc trung binh 3 muo'i la CxHy02Na

1 Hoa tan het ran X gom 0,20 mol Al va 0,15 mol M g can viTa du x mol HNO3

pham khuf khac) Gia t r i x la

A 1,40 B 1,55 C 1,65 D 1,30

• Nhdn xet

Chon bao toan electron la hudng di dung cho bai toan do d day c6 xay ra cac

qua t r i n h oxi hoa khuf Tuy vay, bao toan nguyen to N mdfi la hi/dfng di ngan

bai toan cung c6 the giai theo bao toan kho'i luong nhifng day la loi giai mdm

ra nen tranh vi con phai dung kem bao toan electron

• Giai

+ Dung bao toan electron

Do Al va Fe da cho (0,2.3 + 0,15.2) = 0,9 mol va N*^ da nhan (3a + b) mol electron, ta c6 he:

39

a = 0,2

6 = 0,3

a + b = 0,5 /> = 3o +

0,9

Vay X

= 4«,, , +2n,,,

^ = 4.0,2 + 2.0,3 =

1,4 (mol) Va

y cho

n A

n^,„^,,^ =

+"N/M,(NO,), +"N /No+nN/No,

«x = 3.0,

2 + 2.0,15 +

il

= 1,

4 (mol) Va

Ja

= 0,

2

3a + b = 0,9

0,2.27 + 0,15.24 +

63x = 0,2.213 +

0,15.148 + (30.0,2 +

46.0,3) +1

2 Cha

t be

o A c6 ch

2 C 329,16

5 D 327,61

2

• Nhdn xet i so Co ch

rtlA +

mK OH

= ni

xa phon

g + Dlglixerol +

"^nxidt:

Vay

m xa phong = ( HI

A + m KO H) - (nigUxerol +

n itn ,6 c)

xa phong hoa cac triglixerit)

+ Chi so axit la so mg KOH dung de trung hoa het Itfang axit beo tir do c6 trong 1 gam chat beo

+ Co the d i dang chiing minh i ^ g dang toan nay c6 cong thurc giai nhanh sau:

chat bet) ^ X a '

84000

(Cx la chi so' xa phong hoa; C a la chi so' axit)

+ Neu thay K O H bang NaOH (cac so lieu giOf nguyen) t h i kho'i liicrng

glixerol va midc vSn khong doi, nhung do khoi lifcmg NaOH khac vdfi khoi

liJOng KOH nen khoi liTcfng xa phong thu dugc la:

A 6,40 B 4,00 C 3,00 D 1,60

• Nhdn xet

Do Cu(0H)2tan het trong nUdc NH3 dii nen rSn Z chi la 0,15 mol Fe203 Mat

khac Cu con dii sau phan ufng nen bao toan Fe cho thay dung dich Y phai chufa 0,3 mol FeS04 Hon hop k h i c6 0,1 mol SO2 nen bao toan S cho so mol CUSO4 trong dung dich Y la (0,5 - 0,3 - 0,1) = 0,1 mol CUSO4

Vay da c6 du dCf kien de suf dung dinh luat bao toan khoi liicmg tim ra gia t r i m

41