cĐ2 - btnt

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Bin son v ging dy : Thy gio Nguyn Minh Tun THa Trng THPT Chuyn Hng Vng Ph Th T : 01689 186 513

Pht hnh ti nh sch Khang Vit (71 inh Tin Hong P.aKao Q.1 TP.HCM) Thng 10 2013 1

CHUYN 2: PHNG PHP BO TON NGUYN T

I . Phng php bo ton nguyn t1. Ni dung phng php bo ton nguyn t

- C sca phng php bo ton nguyn t l nh lut bo ton nguyn t : Trong phnngha hc, cc nguyn tc bo ton.- H qu ca ca nh lut bo ton nguyn t :Trong phnng ha hc, tng smol ca mt

nguyn t thamgia phnng bngtngsmol nguyn t to thnh sau phnng.V d : t chy hon ton 6 gam axit axetic cn va V lt O2 (ktc). Sn phm chy hp th

ht vo bnh ng NaOH d, thy khi lng bnh tng mgam. Tnh V v m ?Cc hng t duy tnh V v m :

* Hng 1 :Da vo s mol ca axit axetic (CH3COOH) v phng trnh phnng tnh s molca O2 cn dng, s mol CO2 v s mol H2O to thnh. T suy ra th tch O2 v khi lng bnh

NaOH tng.

Theo gi thit :3CH COOH

6n 0,1 mol.60

= =

Phng trnh phn ng :

CH3COOH + 2O2ot 2CO2 + 2H2O

mol: 0,1 0,2 0,2 0,2

Theo phng trnh v gi thit, ta c :

2

2 2

O (ktc)

bnh NaOH tang CO H O

V 0,2.22,4 4, 48 l t

m m m 0,2.44 0,2.18 12,4 gam

= =

= + = + =

* Hng 2 : Da vo hqu canh lut bo ton nguyn t v s mol axit CH3COOH (0,1 mol) tnh s mol CO2 v s mol H2O to thnh; s mol O2 tham gia phn ng. T suy ra th tch O2v khi lng bnh NaOH tng.

p dng bo ton nguyn ti vi C v H, ta c :

2 3 2

2 3 2

CO CH COOH CO

H O CH COOH H O

n 2n 2.0,1 0,2 n 0,2

2n 4n 4.0,1 0,4 n 0,2

= = = =

= = = =

p dng bo ton nguyn t O, ta c :

{ { {3 2 2 2 2CH COOH O CO H O O

? 0,2 0,20,1

2 n 2 n 2 n n n 0,2 mol.+ = + =14 2 43

Suy ra :

2

2 2

O (ktc)

bnh NaOH tang CO H O

V 0,2.22,4 4, 48 l t

m m m 0,2.44 0,2.18 12,4 gam

= =

= + = + =

- Phng php bo ton nguyn t l phng php gii bi tp ha hc sdng h qu canh lut bo ton nguyn t.

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Pht hnh ti nh sch Khang Vit (71 inh Tin Hong P.aKao Q.1 TP.HCM) Thng 10 20132

2. u im ca phng php bo ton nguyn ta. Xt cc hng gii bi tp sau :

Cu 25 M231: Dn V lt (ktc) hn hp X gm axetilen v hiro c khi lng l m gam iqua ng s ng bt niken nung nng, thu c kh Y. Dn Y vo lng d AgNO3 trong dungdch NH3 thu c 12 gam kt ta. Kh i ra khi dung dch phn ng va vi 16 gam brom v

cn li kh Z. t chy hon ton kh Z c 2,24 lt kh CO2 (ktc) v 4,5 gam H2O. Gi tr ca Vl:A. 11,2. B. 13,44. C. 5,60. D. 8,96.

(thi tuyn sinh Cao ng khi A nm 2007)

Hng dn giiCch 1 : Phng php thng thng Tnh ton theo phng trnh phnng

Theo gi thit ta suy ra Y gm H2 d, C2H2 d, C2H4 v C2H6.

S mol ca cc cht :

2 4 2 2 2 2 2

2

2 2 2 6

C H Br C H d C Ag

COH O CO C H

16 12n n 0,1 mol; n n 0,05 mol;

160 240 n4,5 2,24n 0,25 mol; n 0,1 mol n 0,05 mol.

18 22,4 2

= = = = = =

= = = = = =

Phng trnh phn ng :

C2H2 + H2oNi, t C2H4 (1)

mol: 0,1 0,1 0,1

C2H2 + 2H2oNi, t C2H6 (2)

mol: 0,05 0,1 0,05

C2H2 + 2AgNO3 + 2NH3

ot

C2Ag2 + 2NH4NO3 (3)mol: 0,05 0,05

C2H6 +72

O2oNi, t 2CO2 + 3H2O (4)

mol: 0,05 0,1 0,15

2H2 + O2oNi, t 2H2O (5)

mol: 0,1 (0,25 0,15) = 0,1

Theo cc phn ng ta thy :

2 2 2 2

2 2 2 2 2 2 2 2

H H (1) H (2) H (5)

C H C H (1) C H (2) C H (3)

n n n n 0,3 mol;

n n n n 0,2 mol.

= + + =

= + + =

2 2 2X C H HV V V 0,5.22,4 11,2 l t = + = =

Cch 2 : Sdng phng php bo ton nguyn t

2 2 2 2 2 4 2 2C H d C Ag C H Br H On n 0,05 mol; n n 0,1 mol; n 0,25 mol.= = = = =

p dng bo ton nguyn ti vi H, ta c :

{ {2 2 2 2 4 22 2H C H d C H H OC H ban au0,1 0,250,05

2n 2n 2 n 4 n 2 n+ = + +1 2 3

2 2 2 2 2 2(H , C H ban au) (H , C H ban au) ktcn 0,5 mol V 11,2 l t = =

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b. Nhn xt :Vi cch 1 : Vit nhiu phn ng, mi lin quan vsmol ca cc cht c tnh ton da trn

phn ng. Tuy d hiu nhng phi trnh by di dng, mt nhiu thi gian, ch ph hp vi hnhthc thi t lun trc y.

Vi cch 2 : Mi lin quan vsmol ca cc cht c tnh ton trc tip da vo sbo ton

cc nguyn t

nn khng phi vit phng trnh phn ng.c. Kt lun :So snh 2 cch gii trn, ta thy : Phng php bo ton nguyn t c u im l trong qu

trnh lm bi tp hc sinh khng phi vit phng trnh phn ng, tnh ton n gin da vo sbo ton nguyn tv cho kt qunhanh hn so vi vic tnh ton theo phng trnh phnng.

Nh vy : Nu s dng phng php bo ton nguyn t mt cch hiu qu th c thtng ngktc lmbi so vi vic sdng phng php thng thng.3. Phm vi p dng :

Phng php bo ton nguyn tc thgii quyt c nhiu dng bi tp lin quan n phnng trong ha v c cng nh trong ha hu c.

Mt s dng bi tp thng dng bo ton nguyn t l :+Ion Al3+, Zn2+ tc dng vi dung dch kim (NaOH, Ba(OH)2,...).+ Kh CO2 tc dng vi dung dch kim.+ Tnh smol HNO3, H2SO4 tham gia phnng.+ t chy hp cht, thng l hp cht hu c.+ Thy phn khng hon ton peptit.

4. Bng tnh nhanh smol nguyn t, nhm nguyn t trong phnngT v dtrn ta thy : C th tnh nhanh s mol nguyn t, nhm nguyn t nh sau :Smol nguyn tX hoc nhm nguyn tX =s nguyn thoc nhm nguyn tX trong

n cht, hp cht smol cht .Bng tnh nhanh smol nguyn t, nhm nguyn t

Cht Smol cht Smol nguyn t, nhm nguyn t

Ba(OH)22Ba(OH)

n 22 2Ba(OH) Ba(OH)Ba OH

n n ; n 2n+ = =

H2SO42 4H SO

n 22 4 2 44

H SO H SOH SOn 2n ; n n+ = =

Fe2(SO4)32 4 3Fe (SO )

n 3 22 4 3 2 4 34

Fe (SO ) Fe (SO )Fe SOn 2n ; n 3n+ = =

Al2O32 3A l O

n 3 22 3 2 3Al O A l OAl O

n 2n ; n 3n+ = =

CxHyOzNtx y z tC H O N

n x y z t x y z tC C H O N H C H O N

n x.n ; n y.n ;= =

x y z t x y z tO C H O N N C H O Nn z.n ; n t.n .= =

Ala-Ala-AlaA l a A l a A l a

n

A la A la A la A lan 3n =

Ala-Gly-Ala-Val-Gly-ValAla-Gly-Ala-Val-Gly-Valn

A l a A l a- Gl y- Al a- Val -G ly -V aln 2n ;=

Gly A la-Gly -A la-Val -Gly -Valn 2n .=

i vi cc cht khc ta tnh tng t.

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I I . Phn dng bi tp v cc v dminh ha1. Dng 1: Tnh lng cht trong phnng

Phng php gii- Bc 1: Lp s phn ng biu din qu trnh chuyn ha gia cc cht, thy r bn

cht ha hcca bi ton.- Bc 2 : Nhn dng nhanh phng php gii bi tp : Khi gp bi tp m gia lng cht

cn tnh v lng cht bi cho u c cha cng 1 nguyn thay mt nhm nguyn t th tann dng phng php bo ton nguyn t.

- Bc 3 : Xc nh p dng bo ton nguyn ti vi nguyn t, nhmnguyn tno.- Bc 4 :Thit lp phng trnh bo ton nguyn t. Ngoi ra, kt hp vi cc gi thit khc

lp cc phng trnh ton hc c lin quan. T suy ra lng cht cn tnh.PS :- Trong phng php bo ton nguyn t, nu xc nh sai hoc thiu cc cht cha nguyn t

m ta sdng tnh lng cht th bo ton nguyn tkhng cnng na.

Cc v dminh ha a. Phnng mt giai onV d1: in phn nng chy Al2O3 vi cc in cc bng than ch, thu c m kilogam Al catotv 89,6 m3 (ktc) hn hp kh X anot. T khi ca X so vi H2 bng 16,7. Cho 1,12 lt X (ktc)

phn ng vi dung dch Ca(OH)2 d, thu c 1,5 gam kt ta. Bit cc phn ng xy ra hon ton.Gi tr ca m l

A. 115,2. B. 82,8 . C. 144,0. D. 104,4.(thi tuyn sinh i hc khi B nm2013)

Hng dn gii

Bc 1 : Lp s phnng :Trong phn ng in phn nng chy Al2O3 vi cc in cc lm bng than ch (C), Al sinh ra

catot, O2 sinh ra anot v nh vy anot s b O2 oxi ha thnh CO, CO2, ngoi ra vn c th cn O2d.

S phn ng :pnc

2 3 2 2Al O A l (CO , CO, O )

(catot) (anot)

+

CO2 + CaCO3 CaCO3 + H2OBc 2 :Nhn dng nhanh phng php gii bi tp

Bi tp yu cu tnh khi lng ca Al khi in phn nng chy oxit Al2O3, trong khi li chothng qua thng tin v s mol ca CO2, CO, O2. Nhn thy : Gia hn hp (CO, CO2, O2) v Al2O3u c cha nguyn t O; Gia Al v Al2O3 u c nguyn t Al. y l du hiu chng t bi tpny s s dng phng php bo ton nguyn t.Bc 3 : Xc nh p dng bo ton nguyn ti vi nguyn t, nhm nguyn tno

Da vo gi thit tnh c s mol ca CO2, CO, O2. T tnh c s mol ca Al2O3da vobo ton nguyn t O. Bit c s mol ca Al2O3 s tnh c s mol ca Al da vo bo tonnguyn tAl. Bc 4 :Thit lp phng trnh bo ton nguyn t. T suy ra lng cht cn tnh.

Theo gi thit, ta c :

2 2X CO O CO

89,6n n n n 4 kmol (1)

22,4= + + = =

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2 2

2 2

CO O COX

CO O CO

44n 32n 28nM 16,7.2 33,4

n n n

+ += = =

+ +

2 2CO O CO44n 32n 28n 33, 4.4 133, 6 kg (2) + + = =

2 3 2CO CaCO CO trong hon hp X

1,5 0,015n n 0,015 mol %n .100% 30%.

100 0,05

= = = = =

2CO trong Xn 30%.4 1,2 kmol (3) = =

Thay (3) vo (1), (2), ta c h hai phng trnh hai n. Gii h phng trnh ta c :

2O COn 0,6 kmol; n 2,2 kmol.= =

p dng bo ton nguyn ti vi O v Al, ta c :

{ { {2 3 2 2 2 3

2 3

Al O CO CO O A l O

2,2 1,2 0,6Al

A l Al O A l

5,83n n 2 n 2 n n kmol11,63 m 27. 104,4 kg

11,6 3n 2n n kmol

3

= + + = = =

= =

V d2:t 5,6 gam Fe trong khng kh, thu c hn hp cht rn X. Cho ton b X tc dng vidung dch HNO3 long (d), thu c kh NO (sn phm kh duy nht) v dung dch cha m gammui. Gi tr ca m l:

A. 18,0. B. 22,4. C. 15,6. D. 24,2.

(thi tuyn sinh i hc khi B nm2012)

Hng dn giiV dung dch HNO3 d nn Fe phn ng ht, mui st to thnh l Fe(NO3)3.

Gia lng cht cn tnh l khi lng Fe(NO3)3 v lng cht bit l Fe u c nguyn t

Fe, nn p dng bo ton nguyn ti vi Fe, ta c :3 3 3 3Fe(NO ) Fe Fe(NO )

n n 0,1 mol m 24,2 gam= = =

V d 3:Hp th hon ton 2,688 lt kh CO2 (ktc) vo 2,5 lt dung dch Ba(OH)2 nng amol/l, thu c 15,76 gam kt ta. Gi tr ca a l:

A. 0,032. B. 0,048. C. 0,06. D. 0,04.

(thi tuyn sinh i hc khi A nm2007)

Hng dn giiV

{ {2 3CO BaCO0,12 0,08

n n> nn phn ng cn to ra c mui Ba(HCO3)2 v BaCO3.

Theo bo ton nguyn ti vi C v Ba, ta c kt qu sau :

2 3 3 2

2 2 3

2 3 3 2

CO BaCO Ba(HCO )

Ba(OH ) CO BaCOBa(OH ) BaCO Ba(HCO )

n n 2n2n n n

n n n

= + =

= +

T kt qu trn, ta c :

{ {2 2 3 2Ba(OH ) CO BaCO Ba(OH ) 20,12 0,08?

0,12 n n n n 0,1 a [Ba(OH) ] 0,04M

2,5 = = = = =

14 2 43

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V d 4: Hp th hon ton V lt CO2 (ktc) vo bnh ng 200 ml dung dch X gm NaOH 1M vNa2CO3 0,5M, thu c dung dch Y. Kt tinh dung dch Y (ch lm bay hi nc) thu c 19,9gam cht rn khan. Gi tr V l:

A. 2,24. B. 3,36. C. 5,6. D. 1,12.

(thi thi hc ln 5 THPT Chuyn i hc SPHN, nm hc 2011 2012)

Hng dn giip dng bo ton nguyn t i vi Na ta thy :

{ 2 3Na trong Y Na trong X NaOH Na CO0,2.1 0,2.0,5

n n n 2 n 0,4 mol.= = + =1 2 3

Nu trong dung dch Y ch c Na2CO3 th s mol Na2CO3 l 0,2 mol, khi khi lng cht rnl 21,2 gam; nu Y ch cha NaHCO3 th s mol NaHCO3 l 0,4 mol, khi khi lng cht rn l33,6; cn nu Y cha c hai mui th khi lng cht rn thuc khong (21,2 ; 33,6). Trn thc tkhi lng cht rn ch l 19,9 gam nn xy ra trng hp NaOH d. Nh vy cht rn gm NaOHd v Na2CO3.

Theo gi thit v bo ton nguyn t Na, ta c :

2 3

2 32 3

NaOH d Na CO NaOH d

Na CONaOH d Na CO

40n 106n 19,9 n 0,1

n 0,15n 2n 0,4

+ = =

=+ =

p dng bo ton nguyn t C, ta c :

2 2 3 2 3 2CO Na CO trong Y Na CO trong X CO (ktc)

0,15 0,1

n n n 0,05 V 0,05.22,4 1,12 l t= = = =1 4 2 4 3 1 4 2 4 3

V d5: Cho 200 ml dung dch AlCl3 1,5M tc dng vi V lt dung dch NaOH 0,5M, lng kt tathu c l 15,6 gam. Gi tr ln nht ca V l:

A. 1,2. B. 1,8. C. 2,4. D. 2.


Hng dn giiV

{3

3A l (OH)A l

0,3 0,2

n n+ >1 2 3

nn cn mt phn ion nhm nm trong dung dch sau phn ng.

Phn ng c th xy ra theo hai hng khc nhau :

33

3

34

NaClA l(OH) dd

AlCl d

AlCl

NaClA l(OH) dd

Na[Al(OH) ]

+

+

Theo hng (1) : AlCl3 d, nn lng NaOH dng trong trng hp ny l t nht.

Theo hng (2) : AlCl3 chuyn ht vo kt ta Al(OH)3, sau kt ta b ha tan mt phn.Trng hp ny lng NaOH dng nhiu nht. Vy ta phi tnh lng NaOH theo hng (2).

p dng bo ton nguyn t i vi Al v bo ton nhm OH , ta c kt qu sau :

33 4

33

34

A l (OH)A l [ A l (OH ) ]

A l (OH)A l OHAl(OH)

OH [ A l (OH ) ]

n n n4n n n

n 3n 4n

+

+

= + =

= +

dd NaOH+ (1)

(2)

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T kt qu trn, ta c :

{ {3

3Al (OH ) NaOH dd NaOHAl OH OH

0,3 ? 0,2

4 n n n n 1 mol n 1 mol V 1 : 0,5 2M+ = = = = =1 2 3

PS : bi ny, nu ch ni Gi tr ca V l : ...th phnng c thxy ra theo hng (1)hoc (2). Khi s c hai gi tr ca V tha mn l V(min)ng vi hng (1) v V(max)ng vi

hng (2).

V d 6:Ho tan hon ton m gam ZnSO4 vo nc c dung dch X. Nu cho 110 ml dung dchKOH 2M vo X th thu c 3a gam kt ta. Mt khc, nu cho 140 ml dung dch KOH 2M vo Xth thu c 2a gam kt ta. Gi tr ca m l:

A. 32,20. B. 24,15. C. 17,71. D. 16,10.

(thi tuyn sinh i hc khi A nm 2010)

Hng dn giiBn cht phn ng :

22Zn 2OH Zn(OH)+ +

22 4Zn(OH) 2OH [Zn(OH ) ]

+

Trng hp phn ng ca Zn2+ v OH c hin tng ha tan mt phn kt ta, p dng boton nguyn t Zn v nhm OH , ta c kt qu sau :

2 22 4

22

22 4

Zn(OH)Zn [ Zn(OH ) ]

Zn(OH)Zn OHZn(OH)OH [ Zn(OH ) ]

n n n4n n 2n

n 2n 4n

+

+

= + =

= +

Cho 110 ml KOH 2M (0,22 mol) vo dung dch X (TN1), thu c 3a gam Zn(OH)2. Cho 140

ml dung dch KOH 2M (0,28 mol) vo dung dch X (TN2), thu c 2a gam kt ta. Chng ttrng hp (TN2) kt ta b ha tan mt phn. TN1 kt ta c th b ha tan mt phn hoccha b ha tan.

Nu TN1 kt ta cha b ha tan, p dng bo ton nhm OH TN1; bo ton nhm OH vZn TN2, ta c :

2

44 2

4

Zn(OH ) KOH

ZnSOZnSO K OH Zn(OH )ZnSO

3a2. 0,222n n a 3,6399

n 0,10674n n 2n 2a4n 2. 0,28

99

== =

= = = +

Trng hp ny khng tha mn v TN1 :{ {4ZnSO KOH0,220,1067

2 n n< nn kt ta b ha tan.

Vy TN1 kt ta b ha tan mt phn, ta c :

44

4

4

ZnSOZnSO

ZnSO

ZnSO

3a4n 0,22 2. n 0,199 m 16,1 gam

2a a 2,974n 0,28 2.99

= =

= = =

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V d 7: Ha tan ht hn hp cha 10 gam CaCO3 v 17,4 gam FeCO3 bng dung dch HNO3long, nng. S mol HNO3 tham gia phn ng l:

A. 0,8 mol. B. 0,5 mol. C. 0,7 mol. D. 0,2 mol.(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2011 2012)

Hng dn gii

S phn ng :FeCO3 + CaCO3 + HNO3

ot Fe(NO3)3 + Ca(NO3)2 + NO + CO2 + H2O

p dng bo ton nguyn t Ca, Fe v bo ton electron, ta tnh c s mol ca Ca(NO3)2,Fe(NO3)3 v NO. Sau p dng bo ton nguyn t N, ta tnh c s mol ca HNO3 :

{

3 2 3

3 3 33 3 2 3 3

3

Ca(NO ) CaCO NO

Fe(NO ) FeCO HNO Ca(NO ) Fe(NO ) NO

0,050,1 0,15NO FeCO

n n 0,1 n 0, 05 mol

n n 0,15 n 2 n 3 n n 0,7 mol

3n n 0,15

= = =

= = = + + =

= = 14 2 43 14 2 43

V d 8: Ha tan hon ton hn hp gm 0,18 mol FeS2 v a mol Cu2S bng dung dch HNO3 va thu c dung dch X ch cha mui sunfat v V lt NO (ktc) l sn phm kh duy nht. Gi trca V l:

A. 44,8 lt. B. 22,4 lt. C. 26,88 lt. D. 33,6 lt.

(thi thi hc ln 3 THPT Chuyn Nguyn Hu H Ni, nm hc 2010 2011)

Hng dn giiV phn ng ch to ra mui sunfat nn suy ra trong X c hai mui l CuSO4 v Fe2(SO4)3.

S phn ng :

3 42 HN O2

2 4 32

CuSOCu SNO H O

Fe (SO )FeS

+ +

p dng bo ton nguyn t i vi Cu, Fe, S, ta c :

Cu2S + 2FeS2 3HN O 2CuSO4 + Fe2(SO4)3

mol: 0,09 0,18 0,18 0,09

p dng bo ton electron cho phn ng ca FeS2 v Cu2S vi HNO3, ta c :

{ { {2 2FeS Cu S NO NO NO (ktc)?0,18 0,09

15 n 10 n 3n n 1,2 mol V 26,88 l t+ = = =

V d9: X l hn hp 2 hirocacbon mch h, cng dy ng ng. t chy ht 2,8 gam X cn6,72 lt O2 (ktc). Hp th ton b sn phm chy vo nc vi trong d c m gam kt ta. Gi

trm l:A. 30 gam. B. 20 gam. C. 25 gam. D.15 gam.

Hng dn giiS phn ng t chy hai hirocacbon trong X :

ot2 2 2x y

C H O CO H O (1)+ +

p dng bo ton khi lng v bo ton nguyn t O cho phn ng (1), ta c :

{ {

{

2 2 2

2 2 2

2 2 2 2 2 2

X O CO H O

2,8 CO H O H O0,3.32

O CO H O CO H O CO

0,3

m m 44n 18n44n 18n 12,4 n 0,2

2 n 2n n 2n n 0,6 n 0,2

+ = ++ = =

= + + = =

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p dng bo ton nguyn t C, ta c :

3 2 3CaCO CO CaCOn n 0,2 mol m 0,2.100 20 gam= = = =

V d 10: t chy hon ton 0,1 mol mt axit cacboxylic n chc, cn va V lt O2 (ktc),thu c 0,3 mol CO2 v 0,2 mol H2O. Gi tr ca V l:

A. 8,96. B. 11,2. C. 6,72. D. 4,48.


Hng dn giiCng thc phn t ca axit cacboxylic n chc c dng l CxHyO2.

S phn ng :

CxHyO2 + O2 CO2 + H2O (1)

p dng bo ton nguyn t O cho phn ng (1), ta c :

{ { {x y 2 2 2 2 2 2C H O O CO H O O O (ktc)? 0,3 0,20,1

2 n 2 n 2 n n n 0,3 mol V 6,72 l t+ = + = =1 2 3

V d 11: Hn hp X gm axit axetic, axit fomic v axit oxalic. Khi cho m gam X tc dng viNaHCO3 (d) th thu c 15,68 lt kh CO2 (ktc). Mt khc, t chy hon ton m gam X cn8,96 lt kh O2 (ktc), thu c 35,2 gam CO2 v y mol H2O. Gi tr ca y l:

A. 0,3. B. 0,8. C. 0,2. D. 0,6.


Hng dn giiTheo gi thit, hn hp X gm CH3COOH, HCOOH, HOOC COOH.

Phn ng ca X vi NaHCO3 :

COOH + NaHCO3 COONa + CO2 + H2O (1)

mol: 0,7 0,7Theo (1) v bo ton O trong hn hp X, ta c :

2COOH CO O trong axi t O trong n hom COOH COOHn n 0,7 mol n n 2n 1,4 mol. = = = = =

p dng bo ton nguyn t O trong phn ng t chy hn hp X, ta c :

{ { {2 2 2 2O trong axi t O CO H O H O0,4 0,8 ?1,4

n 2 n 2 n n n 0,6 mol+ = + =14 2 43

V d 12: Tripeptit X v tetrapeptit Y u mch h. Khi thy phn hon ton hn hp gm X v Ych to ra mt amino axit duy nht c cng thc H2NCnH2nCOOH. t chy 0,05 mol Y trong oxi

d, thu c N2 v 36,3 gam hn hp gm CO2, H2O. t chy 0,01 mol X trong oxi d, cho snphm chy vo dung dch Ba(OH)2 d, thu c m gam kt ta. Bit cc phn ng u xy ra honton. Gi tr ca m l

A. 29,55. B. 17,73. C. 23,64. D. 11,82.


Hng dn giiTheo gi thit, suy ra : Amino axit to nn X, Y l amino axit no, mch h, c mt nhm

COOH v mt nhm NH2.

t cng thc phn t ca amino axit l CaH2a+1O2N.

X l tripeptit to ra t amino axit trn c cng thc l C3aH6a-1O4N3.

Y l tetrapeptit to ra t amino axit trn c cng thc l C4aH8a-2O5N4.

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p dng bo ton nguyn t C, H trong phn ng t chy Y, ta c :

{ {2 2CO Y H O Y0,05 0,05

n 4a. n 0,2a; n (4a 1) n 0, 05(4a 1)= = = =

Mt khc, theo gi thit khi t chy Y thu c :

2 2CO H Om m 36,3 0,2a.44 0,05(4a 1)18 36,3 a 3+ = + = =

Vi a = 3 th cng thc phn t ca X l C9H17O4N3.

p dng bo ton nguyn t C trong phn ng t chy X v bo ton nguyn t Ba khi hp thusn phm chy ca X vo dung dch Ba(OH)2 d, ta c :

{3 2 3BaCO CO X BaCO0,01

n n 9 n 0,09 m 0,09.197 17,73 gam= = = = =

PS :Cch thit lp cng thc ca X, Y :X l tripeptit nn cng thc ca X l : (3CaH2a+1O2N 2H2O) = C3aH6a-1O4N3;Y l tetrapeptit nn cng thc ca X l : (4CaH2a+1O2N 3H2O) = C4aH8a-2O5N4.

V d 13: Thy phn ht m gam tetrapeptit Ala-Ala-Ala-Ala (mch h) thu c hn hp gm28,48 gam Ala, 32 gam Ala-Ala v 27,72 gam Ala-Ala-Ala. Gi tr ca m l:

A. 90,6. B. 111,74. C. 81,54. D. 66,44.


Hng dn giiAla (alanin) l tn thng gi ca amino axit CH3 CH(NH2) COOH (M = 89).

S phn ng :

Ala-Ala-Ala-Ala + H2O Ala + Ala-Ala + Ala-Ala-Ala

mol: 0,32 0,2 0,12p dng bo ton nhm Ala, ta c :

{Ala A la A la A la A la A la A la A la A la A la A la A la A la A la0,32 0,2 0,12

4n n 2 n 3n n 0,27 mol. = + + =1 2 3 1 4 2 43

Ala A la A la A la m (4.89 3.18).0,27 81,54 gam = =

PS :Shnh thnh lin kt peptit :H2NCH(R)COOH + HNHCH(R)COOH H2NCH(R)CONHCH(R)COOH + H2O

Nh vy mi mt lin kt peptit hnh thnh th sng thi gii phng 1 phn tH2O.Suy ra :

32 27,720,2 ; 0,12 .

2.89 18 3.89 2.18A l a A la A la A l a A l a n mol n mol

= = = =

y l dng bi tp mi xut hin tnm 2011 v cn c thxut hin trong cc thi nhngnm tip theo. Trc , ta ch gp nhng bi tp p dng bo ton nguyn t hoc nhm nguyntv c nh 23 4, , ,...N O OH SO

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b. Phnng xy ra nhiu giai onV d 14: in phn 200 ml dung dch CuSO4 (dung dch X) vi in cc tr sau thi gian ngngin phn th thy khi lng X gim. Dung dch sau in phn tc dng va vi 500 ml dungdch BaCl2 0,3M to kt ta trng. Cho bit khi lng ring dung dch CuSO4 l 1,25 g/ml; sauin phn lng H2O bay hi khng ng k. Nng mol/lt v nng phn trm ca dung dchCuSO4 trc in phn l:

A. 0,35M, 8%. B. 0,52, 10%. C. 0,75M, 9,6%. D. 0,49M, 12%.

Hng dn gii

Khi in phn dung dch CuSO4, ion2

4SO khng b in phn, nn mol 24SO

trc v sau

in phn khng i.

p dng bo ton gc 24SO v nguyn t Ba, ta c :

4 4 2CuSO BaSO BaCln n n 0,5.0,3 0,15 mol.= = = =

Vy nng mol/lt v nng phn trm ca CuSO4 trc in phn l :

44 CuSO

0,15 0,15.160[CuSO ] 0,75M ; C% .100% 9,6%0,2 200.1,25= = = =

V d 15: Cho hn hp X gm 0,3 mol Fe, 0,15 mol Fe2O3 v 0,1 mol Fe3O4 tc dng ht vi dungdch H2SO4 long thu c dung dch Y. Cho dung dch Y tc dng vi dung dch NaOH d, lckt ta em nung trong khng kh n khi lng khng i thu c m gam cht rn Z. Tnh m.

A. 70. B. 72. C. 65. D. 75.

Hng dn giiS phn ng :

o2 4 2

42dd H SO O , tdd NaOH

2 3 2 4 3 2 33 Z

3 4 2 4

YX

FeSOFeFe(OH)

Fe O Fe (SO ) Fe OFe(OH)Fe O H SO d

+ ++

1 2 3

1 4 2 4 314 2 43

p dng bo ton nguyn t Fe, ta c :

{ { {2 3 2 3 3 4

2 3 2 3

Fe trong Z Fe trong X Fe O trong Z Fe Fe O Fe O

0,3 0,15 0,1?

Fe O trong Z Z Fe O trong Z

n n 2 n n 2 n 3n

n 0,45 mol m m 72 gam

= = + +

= = =

1 4 2 43

V d 16: Nung hn hp gm 11,2 gam Fe; 6,4 gam Cu v 19,5 gam Zn vi mt lng d luhunh n khi phn ng hon ton. Sn phm ca phn ng tc dng vi dung dch HCl d thu

c kh B. Th tch dung dch Pb(NO3)2 20% (d = 1,1 g/ml) ti thiu cn dng hp th ht khB l

A. 752,27 ml. B. 902,73 ml. C. 1053,18 ml. D. 910,25 ml(thi thi hc ln 2 THPT Chuyn Nguyn Hu H Ni, nm hc 2011 2012)

Hng dn giiKhi cho Fe, Cu, Zn phn ng vi S d th sn phm thu c l FeS, CuS, ZnS.Trong cc cht

sn phm ch c FeS v ZnS phn ng c vi HCl, CuS khng phn ng. V vy ta khng cnquan tm n lng Cu ban u.

S phn ng :

{o 3 2dd Pb(NO )S, t dd HCl

2

B

Zn ZnS H S PbSFe FeS

++ +

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p dng bo ton nguyn t i vi cc nguyn t Pb, S, Fe, Zn, ta c :

3 2 2Pb(NO ) PbS H S (FeS, ZnS) Fe Zn

11,2 19,5n n n n n n 0,5 mol

56 65= = = = + = + =

3 2dd Pb(NO )

0,5.331V 752,27 ml

1,1.20% = =

PS :Ta c dd. % . . % .

. %= = = =

m Cm V d C M n n V

M M M d C

(n : s mol, M : khi lng mol, m : khi lng cht tan, mdd : khi lng dung dch, d :khi lng ring ca dung dch, V : th tch ca dung dch, C% : nng phn trmca dungdch.)

V d 17: Cho 13,5 gam hn hp X gm Fe v Zn vo 200 ml dung dch Z cha CuCl2 v FeCl3.Phn ng xong thu c cht rn B nguyn cht v dung dch Y. Cho Y tc dng vi dung dch

NaOH d thu c kt ta D v dung dch E. Sc CO2 n d vo dung dch E, lc kt ta em

nung n khi lng khng i thu c 8,1 gam cht rn. Thnh phn % theo khi lng ca Fev Zn trong X ln lt l:A. 50,85; 49,15. B. 30,85; 69,15. C. 51,85; 48,15. D. 49,85; 50,15.(thi thi hc ln 2 THPT Chuyn Hng Vng Ph Th, nmhc 2010 2011)

Hng dn giiTheo gi thit ta thy : Cht rn B l Cu, dung dch Y c mui ZnCl2, FeCl2 v c th cn CuCl2

d.

S phn ng :

{

o

2 3 2

2

dd (CuCl , FeCl ) COdd NaOH d t2 22 2

2X E

Y

FeClNa ZnOFe

ZnCl Zn(OH) ZnOZn NaOH dCuCl

1 4 2 4 314 2 43

p dng bo ton nguyn t i vi Zn, ta c :

Zn ZnO Zn Fe

8,1 6,5n n 0,1 mol %m .100% 48,15% ; %m 51,85%

81 13,5= = = = = =

V d 18: Ho tan hon ton hn hp X gm 0,2 mol Fe v 0,2 mol Fe2O3 vo dung dch axitH2SO4 long (d), thu c 2,24 lt kh (ktc) v dung dch Y. Cho lng d dung dch NaOH vodung dch Y, sau khi phn ng xy ra hon ton thu c m gam kt ta. Gi tr nh nht ca m l:

A. 54,0. B. 59,1. C. 60,8. D. 57,4.(thi tuyn sinh cao ng nm 2011)

Hng dn giiNu Fe ch phn ng vi H+ th s mol H2 to ra phi l 0,2 mol, trn thc t ch l 0,1. Suy ra

bn cht phn ng l Fe tc dng c vi H+ v vi mui st(III) sinh ra to ra st(II). Nh vymui st(II) sinh ra t Fe v mt t phn mui st(III).

p dng bo ton electron, ta c :

{ {3 3

2Fe H Fe phan ng Fe phan ng0,2 0,1 ?

2 n 2 n n n 0,2 mol.+ += + =1 4 2 43

Vy dung dch Y gm cc cation Fe3+ v Fe2+ :

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{3 3

2 3Fe OFe Fe phan ng

0,2 0,2

n 2 n n 0,2 mol+ += =1 4 2 43

; 2 3Fe ban auFe Fe phan ng0,2 0,2

n n n 0,4 mol.+ += + =14 2 43 1 4 2 43

Theo bo ton nguyn t Fe, ta c :

22

33

Fe(OH) Fe

ket tua (m in)

Fe(OH) Fe

n n 0,4 molm 0,4.90 0,2.107 57, 4 gam

n n 0,2 mol

+

+

= = = + =

= =

PS :ni Gi tr nhnht ca m l : ... v Fe(OH)2 trong hn hp c thtip tc tc dngvi O2 v H2O to thnh Fe(OH)3 lm cho khi lng kt ta tng ln.

V d 19:Ha tan hon ton 0,3 mol hn hp gm Al v Al4C3 vo dung dch KOH (d), thu ca mol hn hp kh v dung dch X. Sc kh CO2 (d) vo dung dch X, lng kt ta thu c l46,8 gam. Gi tr ca a l:

A. 0,60. B. 0,55. C. 0,45. D. 0,40.



2

2

4

4 3

0,3 mol

4 CO3

0,6 mol

dd X

H

CH

Al

A l C

K[Al(OH) ]Al(OH)

KOH d

14 2 43

1 4 2 431 44 2 4 43

Theo s phn ng ta thy : Hn hp kh X l CH4 v H2; 46,8 gam kt ta l Al(OH)3ngvi s mol l 0,6 mol.

Theo gi thit v bo ton nguyn t Al, ta c :

4 3

4 34 3 3

A l A l C A l

A l CA l A l C Al (OH )

n n 0,3 n 0,2

n 0,1n 4n n 0,6

+ = = =+ = =

p dng bo ton nguyn t i vi C v bo ton electron, ta c :

4 4 3 4

4 2

22

CH Al C CHCH H

HH A l

n 3n 3.0,1 n 0,3 a n n 0,6 moln 0,32n 3n 3.0,2

= = = = + = == =

dd KOH

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V d 20: Nung nng m gam hn hp gm Al v Fe3O4 trong iu kin khng c khng kh. Saukhi phn ng xy ra hon ton, thu c hn hp rn X. Cho X tc dng vi dung dch NaOH (d)thu c dung dch Y, cht rn Z v 3,36 lt kh H2 (ktc). Sc kh CO2 (d) vo dung dch Y, thuc 39 gam kt ta. Gi tr ca m l

A. 48,3. B. 57,0. C. 45,6. D. 36,7.

(thi tuyn sinh i hc khi B nm2009)Hng dn giiS phn ng :

o

2

0

2

3

2 38

3 0t3 4

0 0

3CO2

3

H

A l O

Fe O Fe

A l Al d

NaAlOAl(OH)

NaOH d

+

+

+

T s phn ng, ta thy : Cht kh l Al, cht oxi ha l Fe3O4 v H2O trong dung dchNaOH; sn phm kh ca H2O l H2 (0,15 mol). Trong phn ng ton b qu trnh phn ng, s oxi

ha ca Fe gim t83

+ v 0, ca H gim t +1 v 0, ca Al tng t 0 ln +3. Kt ta thu c l

Al(OH)3 vi khi lng l 39 gam ng vi 0,5 mol.p dng bo ton nguyn t i vi Al v bo ton electron, ta c :

{ { { {

3

3 43 4 2

3 4

A l A l (OH )A l

Al Fe OA l Fe O HFe O 0,5.27 0,15.2320,5 0,15?

n n 0,5 n 0,5m m m 48,3 gam3 n 8 n 2 n n 0,15

= = = = + = = + =

1 2 3

V d 21: Nung 2,23 gam hn hp X gm cc kim loi Fe, Al, Zn, Mg trong oxi, sau mt thi gianthu c 2,71 gam hn hp Y. Ha tan hon ton Y vo dung dch HNO3 (d), thu c 0,672 ltkh NO (sn phm kh duy nht, ktc). S mol HNO3 phn ng l

A. 0,12 . B. 0,14. C. 0,16. D. 0,18.(thi tuyn sinh i hc khi B nm 2010)

Hng dn giiThay cc kim loi bng kim loi M. S phn ng :

50

32

n 20 n 2

H N OO 2 n3 n 2

M OM M (NO ) N O H OM d

++

+ +++

+ +

Theo bo ton khi lng, ta c :

{ { {2 2 2X O Y O O2,23 2,71?

0,48m m m m 0,48 gam n 0,015 mol.

32+ = = = =

Cch 1 :Tnh smol HNO3 theo smol N

Theo bo ton electron, ta c : { {23 O NOelectron t rao oiN O tao muoi0,030,015

n n 4 n 3n 0,15 mol. = = + =

1

2(H O NaOH)+

+ +

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Theo bo ton nguyn t N, ta c :3 3

HNO NON O tao m uoin n n 0,15 0,03 0,18 mol= + = + =

Cch 2 :Tnh smol HNO3 theo smol H+Ion H+ tham gia vo 2 phn ng :

4H+ + 3NO + 3e NO + 2H2O

2H+ + 2O H2OSuy ra :

3

32

2

NOH NO

HN O HOH O

n 4n 4n 4.0,03 0,12n n 0,18 mol

n 2n 4n 4.0,015 0,06

+

+

+

= = = = = =

= = = =

V d 22: Hn hp X gm 0,5 mol C2H4 v 0,7 mol H2. Nung nng hn hp X c Ni xc tc mtthi gian, thu c hn hp Y. t chy hon ton hn hp Y c bao nhiu mol H2O ?

A. 1,2. B. 1,7. C. 0,9. D. 0,6.(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2011 2012)

Hng dn giit chy hn hp Y cng chnh l t chy hn hp X (theo bo ton nguyn t v khi lng).

p dng bo ton nguyn t i vi H, ta c :

{ { {2 2 4 2 2H O C H H H O? 0,5 0,7

2 n 4 n 2 n n 1,7 mol= + =

V d 23: Cho hn hp kh X gm HCHO, C2H2 v H2 i qua ng s ng bt Ni nung nng. Saumt thi gian thu c hn hp Y (gm kh v hi). t chy hon ton Y cn dng va 0,07mol O2, sinh ra 0,055 mol CO2 v 0,81 gam H2O. Phn trm th tch ca HCHO trong X l

A. 25,00%. B. 75,00%. C. 66,67%. D. 33,33%.

(thi thi hc ln 1 THPT Chuyn i hc Vinh, nmhc 2012 2013)Hng dn gii

bi ny, nu ch yu cu tnh s mol ca HCHO th ch cn s dng bo ton nguyn t Ol . Nhng yu cu tnh phn trm v th tch ca HCHO nn phi tnh c s mol ca tngcht (1) hoc phi tnh c smol ca HCHO v tng smol ca ba cht (2).

Nu theo hng (1) ta phi p dng bo ton nguyn t i vi c O, C, H.

Ta c :

{ { {

{

{

2 2 2

2 2 2 2 2

2

2 2 2 2

HCHO O CO H O

0,07 0,055 0,045 HCHO

HCHO C H CO C H HCHO

0,055H

HCHO C H H H O

0,045

n 2 n 2n n

n 0,015n 2n n n 0,02 %V 33,33%

n 0,012n 2n 2n 2 n

+ = +

= + = = =

= + + =

Nu theo hng (2) ta ch cn p dng bo ton nguyn t i vi O v H.

Ta c :

{ { {

{

2 2 2

2 2 22 2 2 2

HCHO O CO H O

0,07 0,055 0,045 HCHO

HCHO(HCHO, C H , H )HCHO C H H H O

0,045

n 2 n 2n nn 0,015

%V 33,33%n 0,0452n 2n 2n 2 n

+ = + =

= =+ + =

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V d 24: Oxi ho 2,3 gam ancol etylic bng CuO un nng thu c 3,3 gam hn hp X gmanehit, axit, ancol d v nc. Hn hp ny tc dng vi Na sinh ra 0,84 lt H2 (ktc). Hiu sut

phn ng oxi ho ancol l:A. 25%. B. 50%. C. 75%. D. 90%.

(thi thln 2 Trng THPT Chuyn Hng Vng Ph Th, nm hc 2009 2010

Hng dn giiCch 1 : Gii theo phng php thng thng - Tnh ton theo phnng

Khi lng hn hp X tng ln so vi khi lng ancol ban u l do lng O trong CuO phnng chuyn vo H2O v CH3COOH.

Theo gi thit ta c :

= = = = =

2CuO phan ng O phan ng H

3,3 2,3 0,84n n 0,0625 mol; n 0,0375 mol.

16 22,4

Gi s mol ca ancol tham gia phn ng l x, y v s mol ancol d l z.

Phng trnh phn ng :

CH3CH2OH + CuO CH3CHO + H2O + Cu (1)mol: x x x x

CH3CH2OH + 2CuO CH3COOH + H2O + 2Cu (2)

mol: y 2y y y

2CH3CH2OH + 2Na 2CH3CH2ONa + H2 (3)

mol: z 0,5z

2CH3COOH + 2Na 2CH3COOH + H2 (4)

mol: y 0,5y

2H2O + 2Na 2NaOH + H2 (5)

mol: (x + y) 0,5(x+y)Theo cc phng trnh phn ng v gi thit, ta c :

2 5

2

C H OH

H

CuO

n x y z 0,05 x 0,0125

n 0, 5y 0, 5z (0, 5x 0, 5y ) 0, 0375 y 0, 025

z 0,0125n x 2y 0,0625

= + + = =

= + + + = = == + =

Vy hiu sut phn ng oxi ha ancol l :0,05 0,0125

H .100 75%0,05

= =

Cch 2: p dng bo ton nguyn tS phn ng :

{

o

33

2 5CuO, t Na2 5 2 5 2(1) (2)

0,0375 mol0,05 mol

3

3,3 gam

CH COOHCH COONa

C H OH dC H OH C H ONa H

HOHNaOH

CH CHO

+

14 2 43

1 44 2 4 43

Bn cht phn ng (1) l C2H5OH b oxi ha bi CuO, khi lng hn hp sau phn ng tngln l do O trong CuO chuyn vo H2O v CH3COOH. phn ng (2), CH3COOH, C2H5OH d,H2O c nguyn tH linh ng trong nhm -OH nn tham gia phn ng th Na, CH3CHO khngtham gia phn ng ny.

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Theo gi thit ta c :

= = = = =

2CuO phan ng O phan ng H

3,3 2,3 0,84n n 0,0625 mol; n 0,0375 mol.

16 22,4

Theo bo ton nguyn t O trong CuO phn ng v H trong nhm OH, ta c :

3

2 5

3 2 5 2

HOH CH COOH OCu O phan ng

bao toan nguy en toOC H OH d

HOH CH COOH C H OH d H

bao toan nguyen toH trong n hom OH

n n n 0,0625

n 0,0125.n n n 2n 0,075

+ = =

=+ + = =

1 4 4 4 4 4 2 4 4 4 4 43

1 4 4 4 4 44 2 4 4 4 4 4 43

Vy hiu sut phn ng oxi ha ancol l :0,05 0,0125

H .100 75%0,05

= =

2. Dng 2 : Tm cng thc hp chtNgoi vic sdng tnh lng cht trong phn ng, phng php bo ton nguyn t cn

c dng vo vic tmcng thc ca cc hp cht (thng l hp cht hu c).

Phng php gii- Bc 1 : Da vo gi thit xc nh xemhp cht c cha nhng nguyn t no. i vi

hp cht hu c, khi t chy thng sinh ra CO2 v H2O nn cha thxc nh c ngay hpcht c oxi hay khng trkhi bi cho bit.

- Bc 2 : Sdng bo ton nguyn t tnh s mol cc nguyn t trong hp cht, sdngbo ton khi lng kim xem hp cht c oxi hay khng. T suy ra cng thc n gin nht,cng thc phn thoc c thtm ngayc s lng nguyn tca cc nguyn t trong hp chtsuy ra cng thc phn t.

Cc v dminh ha

V d1:t chy hon ton 20 ml hi hp cht hu c X (ch gm C, H, O) cn va 110 ml khO2 thu c 160 ml hn hp Y gm kh v hi. Dn Y qua dung dch H2SO4 c (d), cn li 80 mlkh Z. Bit cc th tch kh v hi o cng iu kin. Cng thc phn t ca X l

A. C4H8O2. B. C4H10O. C. C3H8O. D. C4H8O.


Hng dn giiDung dch H2SO4 c rt ho nc, nn khi dn Y qua dung dch ny th nc b gi li, kh cn

li thot ra l CO2. Vy2 2CO H O

V 80 ml, V 80 ml.= =

i vi cc cht kh v hi (o cng iu kin nhit v p sut) th t l th tch bng t l

s mol. Nn c th p dng bo ton nguyn t theo th tch ca cc cht.t cng thc phn t ca X l CxHyOz. S phn ng :

CxHyOz + O2 CO2 + H2O

ml: 20 110 80 80

p dng bo ton nguyn t i vi C, H, O, ta c :

4 8

20x 80 x 4

20y 80.2 y 8 X laC H O

20z 110.2 80.2 80 z 1

= =

= = + = + =

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V d 2: t chy 1 lt hi hirocacbon vi mt th tch khng kh (lng d). Hn hp kh thuc sau khi hi H2O ngng t c th tch l 18,5 lt, cho qua dung dch KOH d cn 16,5 lt, chohn hp kh i qua ng ng photpho d th cn li 16 lt. Xc nh CTPT ca hp cht trn bitcc th tch kh o cng iu kin nhit , p sut v O2 chim 1/5 khng kh, cn li l N2.

A. C2H6. B. C2H4. C. C3H8. D.C2H2.

Hng dn giiTheo gi thit, ta c :

2 2 2 2CO O d N O ban auV 2 lt; V 0,5 l t; V 16 lt V 4 l t.= = = =

S phn ng :

CxHy + O2 CO2 + H2O + O2 d

lt: 1 4 2 a 0,5

p dng bo ton nguyn t i vi cc nguyn t C, H, O, ta c :

x 2 x 2

y 2a y 64.2 2.2 a 0,5.2 a 3

= =

= = = + + =

Cng thc ca hirocacbon l 2 6C H

V d 3:t chy hon ton mt hp cht hu c X cn 6,72 lt O2 (ktc). Sn phm chy hp thht vo bnh ng dung dch Ba(OH)2 thy c 19,7 gam kt ta xut hin v khi lng dung dchgim 5,5 gam. Lc b kt ta, un nng nc lc li thu c 9,85 gam kt ta na. CTPT ca Xl:

A. C2H6. B. C2H6O. C. C2H6O2. D. C4H12O2.


{2

0,3 mol

o

3

0,1 mol

O

2x y z

2X

t3 2 3 2

0,05 mol 0,05 mol

BaCO

COC H O

H O

Ba(HCO ) BaCO CO

+

14 2 43

14 2 43

1 4 2 4 3 14 2 43

Theo bo ton nguyn t C, ta c :

{2 3 3 2C trong X CO BaCO Ba(HCO )0,1 0,05

n n n 2 n 0,2 mol.= = + =142 43

Theo gi thit, ta c :

{ {3 2 2 2 2dd giam BaCO CO H O H O H O

0,2.44 ?5,5 19,7

m m (m m ) m 5,4 gam n 0,3 mol.= + = =14 2 43 1 2 3

p dng bo ton nguyn t H, ta c :

2H trong X H On 2n 2.0,3 0,6 mol.= = =

p dng bo ton nguyn t i vi O, ta c :

{ { {2 2 2O trong X O CO H O O trong X0,3 0,2 0,3?

n 2 n 2 n n n 0,1 mol.+ = + =14 2 43

2Ba(OH)

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T l s mol ca cc nguyn t trong X l :

C H On : n : n 0, 2 : 0, 6 : 0,1 2 : 6 : 1= = Cng thc n gin nht ca X l C2H6O.

t cng thc phn t ca X l (C2H6O)n hay C2nH6nOn.

bt bo ha ca X l X2.2n 6n 2

0 n 1 n 12

+ = = .

Vy 2 6C H O chnh l cng thc phn t ca X.

PS :i vi nhng dng bi tp : t chy (oxi ha) hon ton mt hp cht hu c X. Choton bsn phmchy vo bnhng dung dch Ca(OH)2 hoc Ba(OH)2 th :

+ Khi lng bnh tng =2 2

+CO H O

m m .

+ Khi lng dung dch tng =2 2

( )+ CO H O ket tua

m m m .

+ Khi lng dung dch gim =2 2

( ) +CO H O ket tua

m m m .

V d 4:t chy hon ton mt amin n chc X bng mt lng khng kh (cha 80% th tchN2, cn li l O2) va , ch thu c 0,15 mol CO2; 0,175 mol H2O v 0,975 mol N2. Cng thcphn t ca X l

A. C2H7N. B. C9H21N. C. C3H9N. D. C3H7N.

(thi thi hc ln 1 THPT Chuyn i hc Vinh, nmhc 2012 2013)

Hng dn giip dng bo ton nguyn t i vi C v H, ta c :

2 2C CO H H On n 0,15 mol; n 2n 2.0,175 0,35 mol.= = = = =

p dng bo ton nguyn t i vi O trong phn ng t chy X, ta c :

{ {2 2 2 2O khong kh CO H O O khong kh0 ,15 0 ,175?

2 n 2 n n n 0,2375 mol.= + =14 2 43

Trong khng kh, N2 chim 80% v th tch, cn li l O2 nn :

2 2N khong k h O k hong k hn 4n 4.0,2375 0,95 mol.= = =

Suy ra :2 2N trong hchc N N khong kh

0,975 0,95

n 2( n n ) 0,05 mol.= =1 2 3 14 2 43

T l mol ca cc nguyn t trong X l :

C H Nn : n : n 0,15 : 0,35 : 0,05 3 : 7 :1.= =

Dng bt bo ha chng minh c 3 7C H N chnh l cng thc phn t ca X.

PS : Vi bi tp ny ta c th lm nhanh bng cch tnh t lmol C v H ri cn cvo p nsuy ra kt qu.

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V d5 : Ha hi 8,64 gam hn hp gm mt axit no, n chc, mch hX v mt axit no, a chcY (c mch cacbon h, khng phn nhnh) thu c mt th tch hi bng th tch ca 2,8 gam N2(o trong cng iu kin nhit , p sut). t chy hon ton 8,64 gam hn hp hai axit trn thuc 11,44 gam CO2. Phn trm khi lng ca X trong hn hp ban u l

A. 72,22%. B. 65,15%. C. 27,78%. D. 35,25%.

(thi tuyn sinh i hc khi A nm2012)Hng dn giiTheo gi thit : Y l axit no, a chc, mch h, khng phn nhnh. Suy ra : Y l axit no, mch

h, trong phn t c 2 nhm COOH (v nu Y c t 3 nhm COOH tr ln th phi c mchnhnh).

t cng thc phn t ca X l CnH2nO2 v Y l CmH2m-2O4.

Theo gi thit v bo ton nguyn t C, ta c :

n 2n 2 m 2m 2 4 2n 2 n 2

n 2n 2 m 2m 2 4 m 2m 2 4

n 2n 2 m 2m 2 4 2

C H O C H O NC H O

C H O C H O C H O

C H O C H O CO

2,8(1) n n n 0,1 n 0,0428

(2) (14n 32).n (14m 62).n 8,64 n 0,0611,44 0,04n 0,06m 0,26

(3) n.n m.n n 0,2622,4

+ = = = =

+ + + = = + = + = = =

2 4 22 4 2

3 4 4

X : C H On 2 12.0,04%C H O .100 27,78%

Y : C H Om 3 8,64

= = =

=

PS : Th(3) vo (2) c phng trnhn 2n 2 m 2 m 2 4C H O C H O

32n 62n 5 (4).

+ = Kt hp (1) vi (4) tm

c smol ca X v Y.

V d 6:t chy hon ton m gam hn hp X gm hai este ng phn cn dng 27,44 lt kh O2,thu c 23,52 lt kh CO2 v 18,9 gam H2O. Nu cho m gam X tc dng ht vi 400 ml dung dch

NaOH 1M, c cn dung dch sau phn ng th thu c 27,9 gam cht rn khan, trong c a molmui Y v b mol mui Z (MY < MZ). Cc th tch kh u o iu kin tiu chun. T l a : b l

A. 2 : 3. B. 4 : 3 . C. 3 : 2. D. 3 : 5.


Hng dn gii tm cng thc phn t ca hai este trong X ta c th lm nh sau :

Theo gi thit :2 2CO H O

23,52 18,9n 1,05 mol; n 1,05 mol

22,4 18

= = = = .

Suy ra hai este l este no, n chc c cng thc phn t l CnH2nO2.

Theo bo ton khi lng, ta c :

{ { {2 2 2X O CO H O X1, 22 5.32 1, 05 .44 18 ,9

m m m m m 25,9 gam.+ = + =


2

X X X

CO X XX

m (14n 32)n 25,9 n.n 1,05 n 3

n n.n 1,05 n 0,35n 0,35

= + = = = = = ==

Cng thc cu to ca hai este l HCOOC2H5 v CH3COOCH3.

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2

2 5 3 3

CONaOH (HCOOC H vaCH COOCH )

nn 0,4 mol, n 0,35 mol.

3= = =

Suy ra : Cht rn gm a mol HCOONa (Y), b mol CH3COONa (Z) v 0,05 mol NaOH d.

Vy ta c :

a b 0,35 a 0,2a : b 4 : 3

68a 82b 0,05.40 27,9 b 0,15+ = =

= + + = =

V d 7: t chy hon ton 2,76 gam hn hp X gm CxHyCOOH, CxHyCOOCH3, CH3OH thuc 2,688 lt CO2 (ktc) v 1,8 gam H2O. Mt khc, cho 2,76 gam X phn ng va vi 30 mldung dch NaOH 1M, thu c 0,96 gam CH3OH. Cng thc ca CxHyCOOH l:

A. C2H5COOH. B. CH3COOH. C. C2H3COOH. D. C3H5COOH.

Hng dn giit gc CxHy l R.

S mol O trong X l : 2 2CO H OC HO 2,76 12n 2n2,76 m mn 0,0716 16 = = =

p dng bo ton nguyn t i vi O, Na v bo ton gc CH3- , ta c :

3 3

3 3

3 33 3

RCOOH RCOOCH CH OH ban au RCOOH

RCOOH RCOOCH RCOONa NaOH RCOOCH

RCOOCH CH OH sauphan ngCH OH ban au CH OH ban au

2n 2n n 0,07 n 0,01

n n n n 0,03 n 0,02

n n n 0,03 n 0,01

+ + = =

+ = = = =

+ = = =

2 30,01(R 45) 0,02(R 59) 0,01.32 2,76 R 27 (C H ) . + + + + = =

Vy CxHyCOOH l 2CH CH COOH=

V d 8: Cho 100 ml dung dch amino axit X nng 0,4M tc dng va vi 80 ml dung dchNaOH 0,5M, thu c dung dch cha 5 gam mui. Cng thc ca X l

A. NH2C3H6COOH. B. NH2C3H5(COOH)2.

C. (NH2)2C4H7COOH. D. NH2C2H4COOH.


Hng dn giiDo X NaOHn : n 1 :1,= suy ra X ch c mt nhm COOH, X c cng thc l (H2N)nRCOOH.

Ta c :

2 n

2 n

( H N ) RCOON a NaOH

bao toan nguyen toNa

2 3 6

(H N) RCOONa

n n 0,04R 42

X laH NC H COOHn 15

M 1250,04

= = =

= = =

1 4 4 4 2 4 4 43

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I I I . Bi tp p dng1. Bi tp c li giiBi tp dnh cho hc sinh lp 10Cu 1: Cho hn hp X gm 0,15 mol Fe, 0,075 mol Fe2O3 v 0,05 mol Fe3O4 tc dng ht vi dungdch HCl long, thu c dung dch Y. Cho dung dch Y tc dng ht vi dung dch KOH d, lc

kt ta em nung trong khng kh n khi lng khng i thu c m gam cht rn Z. Gi tr cam l :A. 36. B. 72. C. 65. D. 75.

Cu 2: Cho 1,56 gam hn hp gm Al v Al2O3 phn ng ht vi dung dch HCl (d), thu c Vlt kh H2 (ktc) v dung dch X. Nh t t dung dch NH3 n d vo dung dch X thu c ktta, lc ht lng kt ta, nung n khi lng khng i thu c 2,04 gam cht rn. Gi tr ca Vl :

A. 0,672. B. 0,224. C. 0,448. D. 1,344.

(thi tuyn sinh Cao ng nm2010)Cu 3: Cho V lt hn hp kh gm H2S v SO2 tc dng vi dung dch brom d. Thm dung dch

BaCl2 d vo hn hp trn th thu c 2,33 gam kt ta. Gi tr ca V l :A. 0,112 lt. B. 2,24 lt. C. 1,12 lt. D. 0,224 lt.

Cu 4: Cho hn hp Fe v FeS tc dng vi dung dch HCl (d), thu c 2,464 lt hn hp kh(ktc). Dn hn hp kh ny qua dung dch Pb(NO3)2 d, sinh ra 23,9 gam kt ta en. Phn trmkhi lng ca Fe v FeS trong hn hp ln lt l :

A. 94,02% v 5,98%. B. 5,98% v 94,02%.

C. 25% v 75%. D. 75% v 25%.

Cu 5: Cho hn hp X gm SO2 v O2 theo t l s mol 1:1 i qua V2O5 xc tc, un nng thuc hn hp Y c khi lng 19,2 gam. Ho tan Y vo nc sau thm Ba(NO3)2 d thu c

37,28 gam kt ta. Hiu sut phn ng gia SO2 v O2 l :A. 40%. B. 75%. C. 80%. D. 60%.

Cu 6: Ha tan hn hp X gm 11,2 gam Fe v 2,4 gam Mg bng dung dch H2SO4 long (d), thuc dung dch Y. Cho dung dch NaOH d vo Y thu c kt ta Z. Nung Z trong khng kh nkhi lng khng i, thu c m gam cht rn. Bit cc phn ng u xy ra hon ton. Gi trca m l

A. 24. B. 20. C. 36. D. 18.

(thi tuyn sinh i hc khi B nm 2013)Cu 7: em 11,2 gam Fe ngoi khng kh, sau mt thi gian thu c mt hn hp gm Fe vcc oxit. Ha tan hon ton hn hp trong dung dch H2SO4 c, nng d thu c 3,36 lt kh

SO2 (ktc). S mol H2SO4 tham gia phn ng l :A. 0,4 mol. B. 0,3 mol. C. 0,5 mol. D.0,45 mol.

Cu 8: Cho 6 lt hn hp CO2 v N2 (ktc) i qua dung dch KOH to ra 2,07 gam K2CO3 v 6 gamKHCO3. Thnh phn phn trm v th tch ca CO2 trong hn hp l :

A. 42%. B. 56%. C. 28%. D. 50%.

Cu 9: Dng kh CO kh hon ton 2,88 gam hn hp X gm Fe, FeO, Fe2O3 thu c 2,24gam cht rn. Mt khc, ha tan ht 2,88 gam X cn va 100 ml dung dch HCl, kt thc thnghim thu c 224 ml kh (ktc). Nng mol/lt ca dung dch HCl l :

A. 1. B. 0,5. C. 1,6. D. 0,8.

(thi thi hc ln 2 THPT Chuyn i hc SPHN, nm hc 2011 2012)

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Cu 10: Hn hp X gm Fe3O4, FeO, Fe2O3, CuO. Ly 46,7 gam X kh ha hon ton bng H2 ththu c 9 gam H2O. Cng ly 46,7 gam X tc dng vi dung dch HCl d, ri c cn dung dchsau phn ng th thu c khi lng mui khan thu c l

A. 64,95 gam. B. 82,2 gam. C. 74,2 gam. D. 96,8 gam.

(thi thi hc ln 1 THPT Chuyn i hc Vinh, nm hc 2011 2012)

Bi tp dnh cho hc sinh lp 11Cu 11: Cho m gam hn hp Mg, Al vo 250 ml dung dch X cha hn hp axit HCl 1M v axitH2SO4 0,5M, thu c 5,32 lt H2 (ktc) v dung dch Y (coi th tch dung dch khng i). Dungdch Y c pH l :

A. 1. B. 6. C. 7. D. 2.

(thi tuyn sinh i hc khi A nm 2007)Cu 12: Cho 150 ml dung dch KOH 1,2M tc dng vi 100 ml dung dch AlCl3 nng x mol/l,thu c dung dch Y v 4,68 gam kt ta. Loi b kt ta, thm tip 175 ml dung dch KOH 1,2Mvo Y, thu c 2,34 gam kt ta. Gi tr ca x l

A. 1,2. B. 0,8. C. 0,9. D. 1,0.

(thi tuyn sinh i hc khi B nm 2010)Cu 13: Ho tan hon ton hn hp m gam hn hp gm FeS2 v Cu2S vo axit HNO3 (va ),thu c dung dch X (ch cha hai mui sunfat) vi tng khi lng l 72 gam. Gi tr ca m l :

A. 80. B. 20. C. 60. D. 40.

(thi thi hc ln 4 THPT Chuyn i hc Vinh, nm hc 2010 2011)Cu 14: un nng m gam hn hp Cu v Fe c t l khi lng tng ng 7 : 3 vi mt lngdung dch HNO3. Khi cc phn ng kt thc, thu c 0,75m gam cht rn, dung dch X v 5,6 lthn hp kh (ktc) gm NO v NO2 (khng c sn phm kh khc ca N

+5). Bit lng HNO3 phn ng l 44,1 gam. Gi tr ca m l :

A. 44,8. B. 40,5. C. 33,6. D. 50,4.(thi tuyn sinh i hc khi A nm 2011)Cu 15*:Hp th ht V lt kh CO2vo dung dch cha 0,42 mol Ca(OH)2 thu c a gam ktta. Tch ly kt ta, sau thm tip 0,6V lt kh CO2na, thu thm 0,2a gam kt ta. Th tchcc kh o ktc. Gi tr ca V l:

A. 7,84 lt. B. 5,60 lt. C. 6,72 lt. D. 8,40 lt.

(thi thi hc ln 4 THPT Chuyn Nguyn Hu H Ni, nm hc 2011 2012)Cu 16: t chy hon ton m gam hn hp X gm C2H2, C3H6, C6H6 cn va ng V ltkhng kh (ktc). Hp th ton b sn phm chy vo bnh ng nc vi trong d thu c agam kt ta. Bit khng kh gm c 20% oxi v 80% nit theo th tch. Biu thc lin h gia

m vi V v a l

A.V a

m .28 25

= + B.2V a

m .25 28

= + C.V a

m .25 28

= + D.V 2a

m .28 25

= +

Cu 17: Cho 0,5 lt hn hp gm hirocacbon v kh cacbonic vo 2,5 lt oxi (ly d) ri t. Thtch ca hn hp thu c sau khi t l 3,4 lt. Cho hn hp qua thit b lm lnh, th tch hn hpkh cn li 1,8 lt v cho li qua dung dch KOH ch cn 0,5 lt kh. Th tch cc kh c o trongcng iu kin. Tn gi ca hirocacbon l :

A.propan. B. xiclobutan. C.propen. D. xiclopropan.

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Cu 18: Cho 224,00 lt metan (ktc) qua h quang c V lt hn hp A (ktc) cha 12% C2H2;10% CH4; 78% H2 (v th tch). Gi s ch xy ra 2 phn ng :

2CH4 C2H2 + 3H2 (1)

CH4 C + 2H2 (2)

Gi tr ca V l :

A. 407,27. B. 448,00. C. 520,18. D. 472,64.Cu 19: t chy hon ton m gam hn hp X gm hai ancol, thu c 13,44 lt kh CO2 (ktc) v15,3 gam H2O. Mt khc, cho m gam X tc dng vi Na (d), thu c 4,48 lt kh H2 (ktc). Gitr ca m l

A. 12,9 . B. 15,3. C. 12,3. D. 16,9.

(thi tuyn sinh i hc khi B nm 2012)Cu 20*: Hn hp X gm 0,01 mol HCOONa v a mol mui natri ca hai axit no, n chc, mchhl ng ng lin tip. t chy hon ton hn hp X, cho sn phm kh v hi ln lt qua bnh1 ng H2SO4 c, bnh 2 ng KOH thy khi lng bnh 2 tng nhiu hn bnh mt l 3,51 gam.Phn cht rn cn li sau khi t chy X c khi lng l 2,65 gam. Cng thc phn t ca hai

mui natri l :A. C2H5COONa v C3H7COONa. B. C3H7COONa v C4H9COONa.

C. CH3COONa v C2H5COONa. D. CH3COONa v C3H7COONa.

(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2009 2010)Bi tp dnh cho hc sinh lp 12Cu 21: Cho 0,1 mol CH3COOH vo cc cha 30 ml dung dch ROH 20% (d =1,2 g/ml, R l mtkim loi kim). C cn dung dch sau phn ng, ri t chy hon ton cht rn khan cn li. Saukhi t chy th cn li 9,54 gam cht rn v c m gam hn hp gm CO2, hi nc bay ra. Gi trca m l :

A. 10,02. B. 9,3. C. 7,54. D. 8,26.(thi thi hc ln 1 THPT Chuyn KHTN, nm hc 2011 2012)Cu 22*: Cho 2,76 gam cht hu c X gm C, H, O tc dng vi dung dch NaOH va sau chng kh th phn bay hi ch c nc v cn li 2 mui ca Na c khi lng 4,44 gam. Nungnng 2 mui ny trong oxi d, phn ng hon ton thu c 2,464 lt CO2 (ktc); 3,18 gam Na2CO3v 0,9 gam H2O. Bit cng thc phn t ca X trng vi cng thc n gin nht. Cho 2,76 gam Xtc dng vi 80 ml dung dch KOH 1M, c cn dung dch thu c m gam cht rn. m c gi tr l :

A. 6,88. B. 6,52. C. 7,24. D. 6,16.

(thi thi hc ln 2 THPT Chuyn Hng Vng Ph Th, nmhc 2009 2010)Cu 23: un nng m gam hn hp X gm cc cht c cng mt loi nhm chc vi 600 ml dung

dch NaOH 1,15M, thu c dung dch Y cha mui ca mt axit cacboxylic n chc v 15,4 gamhi Z gm cc ancol. Cho ton b Z tc dng vi Na d, thu c 5,04 lt kh H2 (ktc). C cndung dch Y, nung nng cht rn thu c vi CaO cho n khi phn ng xy ra hon ton, thuc 7,2 gam mt cht kh. Gi tr ca m l

A. 40,60. B. 22,60. C. 34,30. D. 34,51.

(thi tuyn sinh i hc khi B nm 2012)Cu 24: Cho X l hexapeptit Ala-Gly-Ala-Val-Gly-Val v Y l tetrapeptit Gly-Ala-Gly-Glu. Thy

phn hon ton m gam hn hp gm X v Y thu c 4 amino axit, trong c 30 gam glyxin v28,48 gam alanin. Gi tr ca m l

A. 77,6. B. 83,2. C. 87,4. D. 73,4.


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Cu 25*: Cho V lt CO2 (ktc) hp th ht trong dung dch cha 0,2 mol Ba(OH)2 v 0,1 molNaOH. Sau phn ng hon ton thu kt ta v dung dch cha 21,35 gam mui. Gi tr ca V l :

A. 7,84. B. 8,96. C. 6,72. D. 7,84 hoc 6,72.

Cu 26: Ha tan ht m gam ZnSO4 vo nc c dung dch X. Cho 110 ml dung dch KOH 2Mvo X, thu c a gam kt ta. Mt khc, nu cho 140 ml dung dch KOH 2M vo X th cng thu

c a gam kt ta. Gi tr ca m lA. 20,125. B. 12,375. C. 22,540. D. 17,710.

(thi tuyn sinh i hc khi A nm 2009)Cu 27*: Cho 500 ml dung dch Ba(OH)2 0,1M vo V ml dung dch Al2(SO4)3 0,1M; sau khi cc

phn ng kt thc thu c 12,045 gam kt ta. Gi tr ca V lA. 75. B. 150. C. 300. D. 200.

(thi tuyn sinh i hc khi A nm 2012)Cu 28: Ha tan 14 gam hn hp Cu, Fe3O4 vo dung dch HCl, sau phn ng cn d 2,16 gamhn hp cht rn v dung dch X. Cho X tc dng vi AgNO3 d thu c bao nhiu gam kt ta ?

A. 45,92. B. 12,96. C. 58,88. D. 47,4.

(thi thi hc ln 2 THPT Chuyn Nguyn Hu H Ni, nm hc 2011 2012)Cu 29: Cho 8,96 lt hn hp 2 kh H2 v CO (ktc) i qua ng s ng 0,2 mol Al2O3 v 0,3 molCuO nung nng n phn ng hon ton thu c cht rn X. X phn ng va trong 0,5 lt dungdch HNO3 c nng aM (sn phm kh l kh NO duy nht). Gi tr ca a l

A. 2,00. B. 2,80. C. 3,67. D. 4,00.

(thi thi hc ln 4 THPT Chuyn i hc Vinh, nm hc 2010 2011)Cu 30: Ha tan ht 10,24 gam Cu bng 200 ml dung dch HNO3 3M c dung dch A. Thm 400ml dung dch NaOH 1M vo dung dch A. Lc b kt ta, c cn dung dch ri nung cht rn nkhi lng khng i thu c 26,44 gam cht rn. S mol HNO3 phn ng vi Cu l :

A. 0,48 mol. B. 0,58 mol. C. 0,56 mol. D. 0,4 mol.(thi thi hc ln 2 THPT Chuyn Nguyn Hu H Ni, nm hc 2010 2011)

2. Bi tp ch cp nCu 31:in phn nng chy Al2O3 khi ti anot thot ra mt hn hp kh gm O2 10%; CO20% v CO2 70%. Tng th tch kh l 6,72 m

3 (ti nhit 819oC v p sut 2,0 atm). Tnh khilng Al thu c ti catot?

A. 2,16 kg. B. 5,40 kg. C. 4,86 kg. D. 4,32 kg.

(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2010 2011)Cu 32: Cho m gam hn hp Al, Fe vo 300 ml dung dch HCl 1M v H2SO4 0,5M, thu c dungdch X v 5,6 lt H2 (ktc). Tnh th tch dung dch NaOH 1M cn cho vo dung dch X thu ckt ta c khi lng ln nht ?

A. 300 ml. B. 500 ml. C. 400 ml. D. 600 ml.

Cu 33: Cho 2,13 gam hn hp X gm ba kim loi Mg, Cu v Al dng bt tc dng hon tonvi oxi thu c hn hp Y gm cc oxit c khi lng 3,33 gam. Th tch dung dch HCl 2M va phn ng ht vi Y l :

A. 90 ml. B. 57 ml. C. 75 ml. D. 50 ml.

(thi tuyn sinh i hc khi A nm 2008)Cu 34: Cho 20 gam hn hp X gm Fe, FeO, Fe3O4, Fe2O3 tan va ht trong 700 ml dung dchHCl 1M thu c 3,36 lt H2 (ktc) v dung dch D. Cho dung dch D tc dng vi NaOH d, lc

kt ta v nung trong khng kh n khi lng khng i thu c cht rn Y. Khi lng Y l :A. 16 gam. B. 32 gam. C. 8 gam. D. 24 gam.

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Cu 35: Cho V lt dung dch NaOH 2M vo dung dch cha 0,1 mol Al2(SO4)3 v 0,1 mol H2SO4n khi phn ng hon ton, thu c 7,8 gam kt ta. Gi tr ln nht ca V thu c lng ktta trn l :

A. 0,35. B. 0,25. C. 0,45. D. 0,05.

(thi tuyn sinh i hc khi A nm 2008)

Cu 36: Hn hp Z gm c Al v Al4C3. Nu cho hn hp Z tc dng vi H2O thu c 31,2 gamAl(OH)3. Nu cho hn hp Z tc dng vi dung dch HCl, ngi ta thu c mt mui duy nht v20,16 lt hn hp kh (ktc). Khi lng ca Al v Al4C3 trong Z l :

A. 14,4 gam v 10,8 gam. B. 10,8 gam v 14,0 gam.

C. 10,8 gam v 14,4 gam. D. 5,4 gam v 7,2 gam.

(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2012 2013)Cu 37: Ha tan ht mt lng Na vo dung dch HCl 10% thu c 46,88 gam dung dch gm

NaCl v NaOH v 1,568 lt H2 (ktc). Nng % NaCl trong dung dch thu c l :

A. 14,97. B. 12,48. C. 12,68. D. 15,38.

Cu 38: Ha tan m gam hn hp gm K v Ca vo nc thu c dung dch A v 5,6 lt H2 (ktc).Hp th 8,96 lt kh CO2 (ktc) vo dung dch A thu c 10 gam kt ta v dung dch B. C cndung dch B thu c 22,5 gam cht rn khan gm hai cht c cng khi lng mol. Gi tr ca ml :


Cu 39: Hp th hon ton 2,24 lt CO2 (ktc) vo 100 ml dung dch gm K2CO3 0,2M v KOH xmol/lt , sau khi cc phn ng xy ra hon ton thu c dung dch Y. Cho ton b Y tc dng vidung dch BaCl2 (d), thu c 11,82 gam kt ta. Gi tr ca x l :

A. 1,0. B. 1,2. C. 1,4. D. 1,6.

(thi tuyn sinh i hc khi B nm 2011)

Cu 40: Cho 3,36 lt kh CO2 vo 200,0 ml dung dch cha NaOH xM v Na2CO3 0,4M thu cdung dch X cha 19,98 gam cht tan. Xc nh nng mol/l ca NaOH trong dung dch ?

A. 0,70M. B. 0,75M. C. 0,60M. D. 0,50M.

(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2010 2011)Cu 41: Hp th ht V lt kh CO2 (ktc) vo 300 ml dung dch hn hp cha ng thi Ba(OH)21M v KOH 1M, thu c 19,7 gam kt ta v dung dch X. Cho KOH d vo dung dch X li thyxut hin thm m gam kt ta na. Gi tr ca V v m ln lt l :

A. 17,92 v 39,4. B. 17,92 v 19,7. C. 17,92 v 137,9. D. 15,58 v 39,4.

(thi thi hc ln 1 THPT Chuyn i hc Vinh, nm hc 2011 2012)Cu 42*: Cho m gam hn hp X gm Ba, BaO, Ba(OH)2 c cng s mol vo nc thu c 500

ml dung dch Y v V lt H2 (ktc). Hp th 3,6V lt CO2 (ktc) vo 500 ml dung dch Y thu c37,824 gam kt ta. Gi tr ca m l :


Cu 43*: Trong mt cc nc c ho tan a mol Ca(HCO3)2 v b mol Mg(HCO3)2. lm mmnc trong cc cn dng V lt nc vi trong, nng pM. Biu thc lin h gia V vi a, b, p l :

A. V = (a +2b)/p. B. V = (a + b)/2p. C. V = (a + b)/p. D. V = (a + b)p.

Cu 44: Cho m gam Al4C3 phn ng va ht vi lng dung dch c 0,03 mol HCl, c dung dchX. Mt khc cho m gam Al4C3 k trn phn ng va ht vi dung dch c 0,04 mol KOH cdung dch Y. Trn ln ton b X v Y k trn vi nhau c hn hp Z cha bao nhiu mol muinhm ?

A. 0,025 mol. B. 0,01 mol. C. 0,04 mol. D. 0,08 mol.(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2011 2012)

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Cu 45*: Ho tan ht m gam Al2(SO4)3 vo nc c dung dch X. Cho 360 ml dung dch NaOH1M vo X, thu c 2a gam kt ta. Mc khc, nu cho 400 ml dung dch NaOH 1M vo X, cngthu c a gam kt ta. Cc phn ng xy ra hon ton, gi tr ca m l:

A. 18,81. B. 15,39. C. 20,52. D. 19,665.

(thi thi hc ln 2 THPT Chuyn Nguyn Hu H Ni, nm hc 2011 2012)

Cu 46*: Cho 240 ml dung dch Ba(OH)2 1M vo 200 ml dung dch hn hp AlCl3 a mol/l vAl2(SO4)3 2a mol/l thu c 51,3 gam kt ta. Gi tr ca a l :

A. 0,12 . B. 0,16 . C. 0,15 . D. 0,2.

Cu 47*: Ha tan 30 gam hn hp gm Al, Zn, Mg trong dung dch HNO3 d. Sau phn ng thuc hn hp kh gm 0,1 mol NO, 0,1 mol N2O v dung dch X. C cn dung dch X thu c 127gam cht rn. S mol HNO3 tham gia phn ng l bao nhiu ?

A. 1,7. B. 1,4. C. 1,9. D. 1,8.

Cu 48: t nng mt hn hp gm Al v 16 gam Fe2O3 (trong iu kin khng c khng kh) nkhi phn ng xy ra hon ton, thu c hn hp rn X. Cho X tc dng va vi V ml dung dch

NaOH 1M sinh ra 3,36 lt H2 (ktc). Gi tr ca V l :

A. 150. B. 100. C. 200. D. 300.Cu 49: Hn hp X gm Fe, FeO, Fe2O3 v Fe3O4. Ho tan hon ton X trong 400 ml dung d chHCl 2M thy thot ra 2,24 lt H2 v cn li 2,8 gam st (duy nht) cha tan. Hy cho bit nu choton b hn hp X vo dung dch HNO3c, nng d thu c bao nhiu lt kh NO2 ?

A. 4,48 lt. B. 10,08 lt. C. 16,8 lt. D. 20,16 lt.

Cu 50*: Ho tan hon ton mt lng hn hp X gm Fe3O4 v FeS2 trong 63 gam HNO3, thuc 1,568 lt NO2 (ktc). Dung dch thu c cho tc dng va vi 200 ml dung dch NaOH2M, lc kt ta em nung n khi lng khng i thu c 9,76 gam cht rn. Nng % cadung dch HNO3 c gi tr l :

A. 47,2%. B. 46,2%. C. 46,6%. D. 44,2%.

(thi HSG Tnh Thi Bnh, nm hc 2011 2012)Cu 51:Kh hon ton m gam FexOy bng CO thu c 8,4 gam kim loi Fe v kh CO2. Hp thhon ton kh CO2 v 500 ml dung dch Ba(OH)2 0,35M th thu c kt ta. Lc kt ta, cho dungdch Na2SO4 d vo dung dch sau phn ng thu c 5,825 gam kt ta trng. Cng thc ca oxitl :

A. FeO hoc Fe2O3. B. Fe2O3 hoc Fe3O4.

C. Fe3O4. D. FeO hoc Fe3O4.

Cu 52: Cho 2,56 gam Cu vo bnh cha 25,2 gam dung dch HNO3 60% n khi phn ng xy rahon ton. Thm tip 210 ml dung dch KOH 1M vo bnh. Phn ng xong, c cn bnh phn ng,nung cht rn thu c ti khi lng khng i c 20,76 gam cht rn. Tnh s mol HNO

3tham

gia phn ng ha tan ng.

A. 0,12 mol. B. 0,1 mol. C. 0,15 mol. D. 0,08 mol.

(thi thi hc ln 1 THPT Chuyn Hng Vng Ph Th, nmhc 2011 2012)Cu 53: t chy hon ton mt hp cht hu c X (C, H, N) bng lng khng kh va (gm1/5 th tch O2, cn li l N2) c kh CO2 , H2O v N2. Cho ton b sn phm chy qua bnh ngdung dch Ba(OH)2 d thy c 39,4 gam kt ta, khi lng dung dch gim i 24,3 gam. Kh thotra khi bnh c th tch 34,72 lt (ktc). Bit

2OXd < 2. CTPT ca X l :

A. C2H7N. B. C2H8N. C. C2H7N2. D. C2H4N2.

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Cu 54:t chy hon ton mt hirocacbon A. Sn phm thu c hp th hon ton vo 200 mldung dch Ca(OH)2 0,2M thy thu c 3 gam kt ta. Lc b kt ta, cn li phn dung dch thykhi lng tng ln so vi ban u l 0,28 gam. Hirocacbon trn c CTPT l :

A. C5H12. B. C2H6. C. C3H8 . D. C4H10.Cu 55: Cho 400 ml mt hn hp gm nit v mt hirocacbon vo 900 ml oxi (d) ri t. Th

tch hn hp thu c sau khi t l 1,4 lt. Sau khi cho nc ngng t cn 800 ml hn hp, ngita cho li qua dung dch KOH thy cn 400 ml kh. Cc th tch kh u o cng iu kin nhit, p sut. Cng thc phn t ca cht hu c l :

A. C3H8. B. C2H4. C. C2H2. D. C2H6.

Cu 56:t chy hon ton mt th tch kh thin nhin gm metan, etan, propan bng oxi khngkh (trong khng kh, oxi chim 20% th tch), thu c 7,84 lt kh CO2 (ktc) v 9,9 gam nc.Th tch khng kh (ktc) nh nht cn dng t chy hon ton lng kh thin nhin trn l :

A. 70,0 lt. B. 78,4 lt. C. 84,0 lt. D. 56,0 lt.

Cu 57: t chy 2 gam hirocacbon A (kh trong iu kin thng) c CO2 v 2 gam H2O. Mtkhc 2,7 gam A tc dng vi dung dch AgNO3/NH3 d c m gam kt ta. Gi tr m l :

A. 8,05 gam. B. 7,35 gam. C. 16,1 gam. D.24 gam.Cu 58: un nng m gam hn hp X gm C2H2, C2H4 v H2 vi xc tc Ni n phn ng xy rahon ton, thu c 8,96 lt (ktc) hn hp Y (c t khi so vi hiro bng 8). t chy hon toncng lng hn hp X trn, ri cho sn phm chy hp th hon ton trong dung dch nc vitrong d th khi lng kt ta thu c l

A. 20 gam. B. 40 gam. C. 30 gam. D. 50 gam.

(thi HSG Tnh Thi Bnh, nm hc 2009 2010)Cu 59: t chy hon ton 3 lt hn hp X gm 2 anken k tip nhau trong dy ng ng cnva 10,5 lt O2 (cc th tch kh o trong cng iu kin nhit , p sut). Hirat ha hon tonX trong iu kin thch hp thu c hn hp ancol Y, trong khi lng ancol bc hai bng 6/13

ln tng khi lng cc ancol bc mt. Phn trm khi lng ca ancol bc mt (c s nguyn tcacbon ln hn) trong Y l

A. 46,43%. B. 31,58%. C. 10,88%. D. 7,89%.

(thi tuyn sinh i hc khi A nm 2012)Cu 60: t chy hon ton 0,1 mol anken X thu c CO2 v hi nc. Hp th hon ton sn

phm bng 100 gam dung dch NaOH 21,62% thu c dung dch mi trong nng ca NaOHch cn 5%. Cng thc phn tng ca X l :

A. C2H4. B. C3H6. C. C4H8. D. C5H10.

Cu 61: Cho hn hp A gm 1 anken v 2 ankan l ng ng lin tip vo mt bnh c dung tch5,6 lt cha O20

oC v 2 atm. Bt tia la in t chy ht hirocacbon, sau a bnh v273oC th p sut trong bnh l p. Nu cho kh trong bnh sau phn ng ln lt i qua bnh 1 ngdung dch H2SO4 c v bnh 2 ng dung dch NaOH thy khi lng bnh 1 tng 3,6 gam, bnh 2tng 7,92 gam. Tnh p bit dung tch bnh thay i khng ng k.

A. 3,04. B. 4,8. C. 5,0. D. 5,2.

Cu 62: t chy hon ton hn hp gm 0,1 mol etilenglicol v 0,2 mol ancol X cn dng 0,95mol kh oxi. Sau phn ng thu c 0,8 mol kh CO2 v 1,1 mol H2O. Cng thc phn t ca X l:

A. C3H6(OH)2. B. C3H5(OH)3. C. C3H5OH. D. C3H7OH.

(thi thi hc ln 2 THPT Chuyn Hng Vng Ph Th, nmhc 2010 2011)

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Cu 63: Cho hn hp kh X gm HCHO v H2 i qua ng s ng bt Ni nung nng. Sau khi phnng xy ra hon ton, thu c hn hp Y gm hai cht hu c. t chy ht Y th thu c 11,7gam H2O v 7,84 lt kh CO2 (ktc). Phn trm theo th tch ca H2 trong X l:

A. 65,00%. B. 46,15%. C. 35,00%. D. 53,85%.


Cu 64: Cho a mol hn hp X gm HCHO, OHC CHO v H2 i qua ng ng bt Ni nung nng,sau mt thi gian thu c hn hp Y gm kh v hi. t chy hon ton hn hp Y, sinh ra 8,1gam nc. Gi tr ca a l :

A. 0,3. B. 0,25. C. 0,45. D. 0,5.

(thi thi hc ln 3 THPT Chuyn i hc Vinh, nm hc 2011 2012)Cu 65: t chy hon ton 1 mol hn hp X gm 1 ancol n chc v mt anehit n chc cn76,16 lt O2 (ktc) to ra 54 gam H2O. T khi hi ca X i vi H2 l :

A. 32,4. B. 36,5. C. 28,9. D. 25,4.

Cu 66: Hn hp X gm axit fomic, axit acrylic, axit oxalic v axit axetic. Cho m gam X phn nght vi dung dch NaHCO3 thu c 1,344 lt CO2 (ktc). t chy hon ton m gam X cn 2,016

lt O2 (ktc), thu c 4,84 gam CO2 v a gam H2O. Gi tr ca a lA. 1,62. B. 1,80. C. 3,60. D. 1,44.

(thi tuyn sinh i hc khi A nm 2012)Cu 67: t chy hon ton 3,42 gam hn hp gm axit acrylic, vinyl axetat, metyl acrylat v axitoleic, ri hp th ton b sn phm chy vo dung dch Ca(OH)2 (d). Sau phn ng thu c 18gam kt ta v dung dch X. Khi lng X so vi khi lng dung dch Ca(OH)2 ban u thayi nh th no ?

A. Tng 2,70 gam. B. Gim 7,74 gam. C. Tng 7,92 gam. D. Gim 7,38 gam.(thi tuyn sinh i hc khi A nm 2011)

Cu 68: Hn hp X gm 1 mol aminoaxit no, mch hv 1 mol amin no, mch h. X c kh nngphn ng ti a vi 2 mol HCl hoc 2 mol NaOH. t chy hon ton X thu c 6 mol CO2, xmol H2O v y mol N2. Cc gi tr x, y tng ng l

A. 8 v 1,0. B. 8 v 1,5. C. 7 v 1,0. D. 7 v 1,5.

(thi tuyn sinh i hc khi A nm 2010)Cu 69*: Hn hp X gm 2 amino axit no (ch c nhm chc COOH v NH2 trong phn t),trong t l O Nm : m 80 : 21.= tc dng va vi 3,83 gam hn hp X cn 30 ml dung dchHCl 1M. Mt khc, t chy hon ton 3,83 gam hn hp X cn 3,192 lt O2 (ktc). Dn ton bsn phm chy (CO2, H2O v N2) vo nc vi trong d th khi lng kt ta thu c l

A. 20 gam. B. 13 gam. C. 10 gam. D. 15 gam.

(thi tuyn sinh i hc khi A nm 2012)Cu 70*: Tripeptit M v tetrapeptit Q u c to ra t mt amino axit X mch h, phn t cmt nhm -NH2. Phn trm khi lng ca N trong X l 18,667%. Thu phn khng hon ton mgam hn hp M, Q (t l mol 1 : 1) trong mi trng axit thu c 0,945 gam M; 4,62 gam ipeptitv 3,75 gam X. Gi tr ca m l

A. 8,389. B. 58,725. C. 5,580. D. 9,315.

(thi thi hc ln 4 THPT Chuyn i hc Vinh, nm hc 2010 2011)

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Phn tch v hng dn gii

1A 2A 3D 4B 5C 6A 7D 8C 9A 10C

11A 12A 13D 14D 15C 16D 17A 18A 19B 20A

21D 22B 23A 24A 25A 26A 27B 28C 29D 30C

31C 32D 33C 34D 35C 36C 37A 38A 39C 40D

41A 42B 43A 44B 45A 46C 47C 48D 49C 50B

51D 52A 53A 54A 55D 56A 57A 58B 59D 60A

61B 62B 63B 64C 65D 66D 67D 68C 69B 70A

Cu 1:S phn ng :

o2

22 O , tdd HCl dd K OH

2 3 3 2 3

3 Z3 4

YX

FeClFeFe(OH)

Fe O FeCl Fe OFe(OH)

Fe O HCl d

++ +

1 2 3

14 2 4314 2 43

Ta thy, hn hp cht rn X v cht rn Z (Fe2O3) u cha nguyn t Fe. Mt khc, s molca cc oxit trong X u bit, nn p dng bo ton nguyn t Fe ta s tnh c s mol caFe2O3 trong Z.

Ta c :

{ { {2 3 2 3 3 4 2 3Fe trong Z Fe trong X Fe O trong Z Fe Fe O Fe O Fe O trong Z0,15 0,075 0,05?

n n 2 n n 2 n 3n n 0,225 mol.= = + + =142 43

Vy khi lng cht rn Z l :2 3Z Fe O trong Z

m m 0,225.160 36 gam= = =

Cu 2:S phn ng :

o3

2

2 3

1,56 gam

3 dd NH t3 2 3

0,02 mol

H

A l

A l O

AlCll (OH) A l O

HCl d

14 2 43

12 3

Cht rn thu c sau phn ng l Al2O3.

Theo gi thit v bo ton nguyn t Al, ta c :

2 3

2 3 2 32 3

A l Al OA l

A l A l O A l O thu cA l O

0,02

27n 102n 1,56n 0,02

n 2n 2 n 0,04 n 0,01

+ ==

+ = = =

1 4 2 4 3


{{

2 2 2A l H H H (ktc)

0,02 ?

3n 2 n n 0,03 mol V 0,03.22,4 0,672 l t= = = =

dd HCl

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Cu 3:S phn ng :

2 2dd Br dd BaCl d2 2 44

2

H S H SOBaSO

SO HBr

Ta c : 2 2 4 2 2(H S, SO ) BaSO (H S, SO ) ktcbao toan nguy en toS

n n 0,01 mol V 0,01.22,4 0,224 lt= = = =1 4 4 2 4 4 3

Cu 4:S phn ng :

{3 22 dd Pb(NO )dd HCl

0,1mol2

0,11 mol

HFePbS

FeS H S++

14 2 43

Hn hp kh thu c gm H2 v H2S. Cho hn hp kh ny phn ng vi Pb(NO3)2 th ch cH2S phn ng to kt ta PbS.

Theo gi thit v p dng bo ton nguyn ti vi S, ta c :

2 2 2

2 2

H S H FeS H S

FeS H S PbS H

n n 0,11 n n 0,1

n n n 0,1 n 0,01

+ = = =

= = = =


{2Fe H Fe0,01

2n 2 n n 0,01 mol.= =

Vy phn trm v khi lng ca FeS v Fe trong hn hp l :

0,1.88

%FeS .100% 94,02% ; %Fe (100 94,02)% 5,98%0,1.88 0,01.56= = = =+

Cu 5:S phn ng :

{

o2 5 3 22t , V O Ba(NO )H O2 2 2 32

432 2 4

X Y

(SO ,O ) d H SOSOBaSO

SOO H SO

1 44 2 4 43

Trong hai axit H2SO3 v H2SO4 th ch c H2SO4 phn ng to kt ta vi Ba(NO3)2.

Theo gi thit v bo ton khi lng ( X Ym m= ), ta c :

2 2 2

2 2 2

O SO O

O SO SO

n : n 1:1 n 0,2

32n 64n 19,2 n 0,2

= =

+ = =

p dng bo ton nguyn t i vi S, ta c :

2 3 2 4 4SO phan ng SO H SO BaSO

37,28n n n n 0,16 mol.

22,4= = = = =

Vy hiu sut phn ng tng hp SO3 t SO2 v O2 l :

2

2

SO phan ng

SO ban au

n 0,16H .100% .100% 80%

n 0,2 = = =

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PS :Phnng tng hp SO3 :

2SO2 + O2o

2 5t , V O 2SO3

T lmol phnng l : 2

2

SO

O

n 2

n 1=

Nu 2

2

21

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Cu 10:Kh hon ton hn hp X bng H2 hay cho X tc dng vi HCl d th O trong X (thc cht l

trong cc oxit) u chuyn ht vo H2O.

p dng bo ton nguyn ti vi O v H, ta c :

2

2

O trong X H O

HCl H O

n n 0,5

n 2n 1

= =

= =

p dng bo ton khi lng, ta c :

{ { { {2X HCl H Omuoi muoi46 ,7 1. 36 ,5 ? 0,5.18

m m m m m 74,2 gam+ = + =

Cu 11:p dng bo ton nguyn t H, ta c :

{ {

{

2 4

2

HCl H SOH ban au0,25.1 0,25.0,5

H trong Y H ban au H phan ngHH phan ng0,5 0,475

0,2375

n n 2 n 0,5

n n n 0,025n 2 n 0,475

+

+ + +

+

= + =

= == =

14 2 43 142 43

Vy nng H+ v pH ca dung dch Y l :

0,025[H ] 0,1M pH lg[H ] 1

0,25+ += = = =

Cu 12:T gi thit, ta nhn thy bn cht ca phn ng l : Cho (150 + 175) ml dung d ch KOH 1,2M

vo dung dch AlCl3 x mol/lt, thu c (4,68 + 2,34) gam Al(OH)3 kt ta.

V3OH t r ong K O H O H t rong A l ( OH )

n n > nn suy ra phn ng cn to ra c mui tan K[Al(OH)4].

Cch 1 : Sdng bo ton nguyn ti vi K, Al, ClTa c :

{ 4

3 4

3 3 4

3 4

3

KOH K Cl K [ A l (OH ) ]

0,39AlCl K [A l (OH ) ]

A lCl A l (OH ) K [ Al (OH ) ]Al Cl K [A l (OH ) ]

0,09

A lCl KCl

(1) n n n

3n n 0,39(2) n n n

n n 0,09

(3) 3n n

= + + =

= + =

=

1 2 3

T h trn ta suy ra :

3

4

AlCl

3K [ A l ( OH ) ]

n 0,12 0,12[A lCl ] 1,2M

n 0,03 0,1

= = =

=

PS : Thay (3) vo (1) ta c hhai phng trnh hai n l3AlCl

n v4[ ( ) ]K A l OH

n .

Cch 2 : Sdng bo ton nguyn tAl v nhmOH Ta c :

{ 3 4

4

33 3 4

KOH A l (OH ) K [ A l (OH ) ]

0,39 K [A l (OH) ]0,09

3

AlClA lCl A l (OH ) K [ A l (OH ) ]

0,09

n 3n 4nn 0,03

[A lCl ] 1,2M

n 0,12n n n

= + =

=

== +

1 2 3

1 2 3

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Cch 3 : Sdng biu thc kt hp gia bo ton nguyn tAl v nhmOH Ta c :

{ {3 3 3A lCl KOH Al (OH ) A lCl 30,39? 0,09

4 n n n n 0,12 [A lCl ] 1,2M = = =1 2 3

PS : Nh vy, vn l sdng bo ton nguyn t, nhng vic la chn sdng bo tonnguyn t i vi nhng nguyn t, nhm nguyn t no l iu ht sc quan trng. V iu squyt nh n tc tnh ton trong qu trnh lm bi.

Cu 13:Theo gi thit suy ra : Trong X c hai mui l CuSO4 v Fe2(SO4)3.

p dng bo ton nguyn ti vi Cu, Fe, S, ta c :

Cu2S + 2FeS2 3HN O 2CuSO4 + Fe2(SO4)3

mol: x 2x 2x x

t s mol ca Cu2S l x mol. Theo s phn ng v gi thit, ta c :

{ 4 2 4 3CuSO Fe (SO )2x x

160 n 400 n 72 720x 72 x 0,1 mol.+ = = =14 2 43

Vy khi lng hn hp ban u l :

2 2Cu S FeSm m m 0,1.160 0,2.120 40 gam= + = + =

Cu 14:Theo gi thit, suy ra : Trong hn hp kim loi c 0,7m gam Cu v 0,3m gam Fe.

Sau phn ng vi dung dch HNO3, khi lng cht rn cn li l 0,75m > 0,7m. Suy ra Fe cnd 0,05m gam v Cu cha phn ng, mui st to ra l Fe(NO3)2.

p dng bo ton nguyn t i Fe v N, ta c :

{

3 2

3 3 2 2

Fe(NO ) Fe phan ng

HNO Fe(NO ) (NO, NO )

0,7 0,25

0,25mn n0,25m56 0,7 2. 0,25 m 50,4 gam

n 2n n 56

= = = + =

= +

14 2 43

Cu 15 :Phng trnh phn ng :

CO2 + Ca(OH)2 CaCO3

CO2 + CaCO3 + H2O Ca(HCO3)2

Theo gi thit :Hp th ht V lt kh CO

2vo dung dch cha 0,42 mol Ca(OH)

2 (1)thu c

a gam kt ta. Tch ly kt ta, sau thm tip 0,6V lt kh CO2na (2), thu thm 0,2a gam ktta.

Suy ra : trng hp (1) Ca(OH)2 d, CO2 chuyn ht vo kt ta. trng hp (2) kt ta b

ha tan mt phn (nu kt ta khng b ha tan th lng kt s tng0,6Va

0,6a gamV

= ), CO2 mt

phn chuyn vo kt ta, phn cn li nm trong Ca(HCO3)2.

Tng s mol CO2 phn ng l1,6V22,4

, tng s mol CaCO3 to ra l :1,2a100

.

(1), ta c : 2 3CO CaCOV a

n n (* )22,4 100= =

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Tng hp (1) v (2), ta c :

2 2 3Ca(OH ) CO CaCO

1,6V 1,2a2n n n 2.0,42 (* * )

22,4 100 = =

T (*) v (**), ta c :

V a

V 6, 7222,4 1001,6V 1,2a a 30

2.0,4222,4 100

= =

= =

Cu 16:S mol O2 tham gia phn ng t chy l :

2O khong kh

1 1 Vn n .

5 5 22,4= =

p dng bo ton nguyn ti vi C, ta c :

2 3C CO CaCO an n n 100= = =

p dng bo ton nguyn ti vi O, ta c :

2 2 2O CO H O2n 2n n= +

Thay mol O2 v mol CO2 vo phng trnh bo ton O, ta c :

2 2H O H H O

V a V an n 2n .

56 50 28 25= = =

Vy khi lng hn hp X l :

C Hm m

a V a 2a Vm 12.100 28 25 25 28= + = +1 2 3 14 2 43

Cu 17:

Theo gi thit, ta c :2 2 2H O CO O d

V 1,6 l t, V 1,3 l t, V 0,5 l t.= = =

S phn ng :

(CxHy + CO2) + O2 CO2 + H2O + O2 d

lt: a b 2,5 1,3 1,6 0,5

Theo gi thit v p dng bo ton nguyn t i vi C, H, O, ta c :

a b 0,5 b 0,1ax b 1,3 a 0,4

ay 1,6.2 x 3

2b 2,5.2 1,3.2 1,6.1 0,5.2 y 8

+ = = + = =

= = + = + + =

Cng thc ca hirocacbon l 3 8C H

Cu 18:S phn ng :

{ }hoquang i en4 2 2 2 4hon hp A

CH C H (12%); H (78%); CH d (10%) C + 1 4 4 4 4 4 4 4 4 2 4 4 4 4 4 4 4 43

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Gi s th tch ca hn hp l 100V th th tch caC2H2; CH4; H2 trong hn hp A ln lt l12V; 10V; 78V.

p dng bo ton nguyn t i vi H ta c :

{ {2 2 4 24 C H CH d H ACH ban au12V 78V10V224

4 V 2 V 4 V 2 V V 4,0727 V 100V 407,27 lt= + + = = =1 2 314 2 43

Cu 19:p dng bo ton nguyn t i vi C, H, O, ta c :

{ { {

2

2

2

C t ron g anco l CO

H trong ancol H O ancol C H O

1,70,6.12 0,4.16O trong ancol OH H

n n 0,6

n 2n 1,7 m m m m 15,3 gam

n n 2n 0,4

= =

= = = + + =

= = =

Cu 20:

t cng thc phn t trung bnh ca hai axit no, n chc, mch hl 2n 2nC H O th mui natri

ca hai axit l2n 2 n 1

C H O N a.

Theo bo ton nguyn t Na, C, H, ta c :

2 2 3n 2 n 1

2n 2 n 1

2 2 3 2 2n 2 n 1

2

2 2n 2n 1

HCOONa C H O Na Na CO

C H O Na0,01 0,025

CO Na CO HCOONa C H O Na CO

0,010,025H O

H O HCOONa C H O Na

0,01

n n 2 nn 0,04

n n n n.n n 0,04n 0,015

n 0,04n 0,012n n (2n 1).n

+ = =

+ = + =

= = +

14 2 43 1 2 3

14 2 431 2 3

14 2 43

5

Theo gi thit, ta thy :

2 2CO H Om m 3, 51 44(0, 04n 0, 015) 18(0, 04n 0, 015) 3, 51 n 3, 75. = = =

Vy cng thc ca hai mui l 2 5 3 7C H COONa vaC H COONa

Cu 21:Sau tt c cc phn ng, R trong ROH chuyn ht vo R2CO3.

p dng bo ton nguyn ti vi R, ta c :

2 3ROH R CO

30.1,2.20% 9,54n 2n 2. R 23 (Na)

R 17 2R 60= = =

+ +

Vi l Na, ta c : 2 3ROH R COn 0,18 mol; n 0,09 mol.= =

S phn ng :

{

o2

2

0,1

3

0,1mol

cocan, O , t 232 3

20,09 mol

m gam

H O

CH COOH

COCH COORR CO

H OROH d

+

1 4 2 4 3

1 2 314 2 43

{

0,18 mol

ROH

(2)

(1)

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p dng bo ton nguyn t i vi C v H, ta c :

{ {

{

3 2 3 2

2

3 2 2 2

CH COOH R CO CO

?0,09 CO0,1

CH COOH ROH H O (1) H O (2) H O (2)

0,18 0,1 ?0,1

2 n n nn 0,11

4 n n 2 n 2 n n 0,19

= + =

+ = + =

14 2 43

1 2 3 1 2 314 2 43

2 2CO H O (2)m m m 8,26 gam = + =

Cu 22:Theo gi thit suy ra : X l este ca phenol.

S phn ng :

{

o2

2

0,11 molO , t

2 3

24,44 gam 0,03 mol

0,05 mol

2,76 gam

2

CO

2 muoi Na Na COH O

X

H O

+

1 2 3

1 4 2 4 3 14 2 431 2 3

Bi tp ny c hai phn ng : (1) : X + NaOH; (2) : 2 mui Na + O2.

Bo ton nguyn t Na :2 3NaOH Na CO

n 2n 2.0,03 0,06 mol.= = =

Bo ton nguyn t C :{2 2 3trong X CO Na CO

0,11 0,03

n n n 0,14 mol.= + =1 2 3

Bo ton khi lng cho phn ng (1) :

{ { 2 2 2X NaOH H O (1) H O (1) H O (1)muoi2,76 4,440,06.40 ?m m m m m 0,72 n 0,04 mol.+ = + = =1 2 3 1 2 3

Bo ton nguyn t H :

{ 2 2H trong X NaOH H O (1) H O (2) H trong X0,06 0,04 0,05

n n 2 n 2 n n 0,12 mol.+ = + =1 2 3 1 2 3

Bo ton khi lng trong phn t X :

X C HO trong X

m m m 2,76 0,14.12 0,12n 0,06 mol

16 16

= = =

T l s mol cc nguyn t trong X :

C H O 7 6 3n : n : n 0,14 : 0,12 : 0,06 7 : 6 : 3 CTGN cua X laC H O .= =

V cng thc phn t trng vi cng thc n gin nht nn cng thc phn t ca X lC7H6O3. Cng thc cu to ca X l HCOOC6H4OH (c 3 ng phn o, m, p).

Phn ng ca X vi ung dch KOH :

HCOOC6H4OH + 3KOH HCOOK + C6H4(OK)2 + 2H2O

mol: 0,02 0,08 (d) 0,04

Theo bo ton khi lng suy ra : muoim 2,76 0,08.56 0,04.18 6,52 gam= + =

o

NaOH, t

(2)

(1)

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Cu 23:Theo gi thit suy ra X gm cc este.

Thy phn este :

R C O + NaOHot R C ONa + OH (1)

O O

Nung ROONa vi NaOH trong CaO

RCOONa + NaOHoCaO, t RH + Na2CO3 (2)

Ta c :

2OH (ancol ) H

bao toan H t rong nh om OH RCOO

NaOH phan ng RCOONa OH (anco l )

theo phan ng (1)

RCOON a N aOH d NaOH ban au

bao toan nguy en toNa

n 2n 0,45n

n n n

n n n 0,69

= =

= =

+ = =

1 4 4 2 4 4 3

1 4 4 4 4 44 2 4 4 4 4 4 43

1 4 4 4 4 4 2 4 4 4 4 4 3

Na

NaOH phan ng

NaOH d

0,45

n 0,45

n 0,24

=

= =

V R COON a N aOH dn n> nn s mol RH c tnh theo mol NaOH d :

RH NaOH d RH 2 5

7,2n n 0,24 M 30 R 29 (C H ).

0,24= = = = =

p dng bo ton khi lng, ta c :

{ {2 5X NaOH phan ng C H COONa ancol X? 15,40,45.40 0,45.96

m m m m m 40,6 gam+ = + =1 4 2 4 3 1 4 2 4 3

Cu 24:t X A la-Gly -A la-Val -Gly-Val Y Gly-A la-Gly -Glun n x mol; n n y mol.= = = =

{ { { { { { { {2 2X A la Gly V al H O Y A la Gly Glu H O89 117 89 14775 7518 18

M 2 M 2 M 2 M 5M 472; M M 2 M M 3M 332.= + + = = + + =

Theo bo ton nhm Gly v nhm Ala, ta c :

Ala Ala-Gly-Ala-Val -Gly-Val Gly-Ala-Gly-Glu

x y

Gly Ala-Gly-Ala-Val -Gly-Val Gly-Ala-Gly-Glux y

28,48n 2 n n 0,32

89 x 0,12

30 y 0,08n 2 n 2 n 0,4

75

= + = =

=

= = + = =

1 4 44 2 4 4 43 1 4 2 4 3

1 4 44 2 4 4 43 1 4 2 4 3

Suy ra :{ {X Y

0,12.472 0,08.332

m m m 83,2 gam= + =

Cu 25:

Trong dung dch mui, nu cn Ba2+ th khng th cn 23CO . Vy dung dch mui c th cha

cc cht :+ Ba(HCO3)2 v NaHCO3 hoc ch c NaHCO3 (1)

+ Na2CO3, NaHCO3 hoc 1 trong hai mui (2)

Gi s xy ra trng hp (2) th trong dung dch ch cha mui Na vi s mol Na l 0,1 mol (doban u c 0,1 mol NaOH). Nu ch c mui Na2CO3 th s mol Na2CO3 l 0,05 nn khi lng

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mui l 5,3 gam. Nu ch c mui NaHCO3 th s mol NaHCO3 l 0,1 mol nn khi lng mui l8,4 gam. Nh vy khi lng mui u nh hn 21,35. Vy phi xy ra trng hp (1)

S phn ng :

3

2

3 2

3

21,35 gam

BaCO

CO

Ba(HCO )NaHCO

1 44 2 4 43

Bo ton nguyn t Na :3NaHCO NaOH

n n 0,1 mol.= =

Theo gi thit :

3 3 2 3 2NaHCO Ba(HCO ) Ba(HCO )

0,1 ?

84 n 259 n 21,35 n 0,05 mol.+ = =1 2 3 14 2 43

Bo ton nguyn t Ba :{ 3 3 2 2 3BaCO Ba(HCO ) Ba(OH ) BaCO

? 0,20,05

n n n n 0,15 mol.+ = =14 2 4314 2 43

Bo ton nguyn t C :

{ {2 3 3 2 3 2 2CO BaCO Ba(HCO ) NaHCO CO CO (ktc)? 0,15 0,05 0,1

n n 2 n n n 0,35 mol V 7,84 l t= + + = =142 43 1 2 3

Cu 26 :Khi cho 110 ml dung dch KOH 2M (TN1) hoc cho 140 ml dung dch KOH 2M (TN2) vo

dung dch cha m gam ZnSO4 u thu c a gam kt ta. Chng tTN1 kt ta Zn(OH)2 chab ha tan

cĐ2 - btnt

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