PP7-Cac Dang Quy Doi

8/4/2019 PP7-Cac Dang Quy Doi

1/12

Phuong phap 7: Cac dang quy d3i

P H lf O 'N G P H A p 7/!llutdr'fl f- 'u ijt ~ a o i

I. CO SO CVA PHUONG PHAp1.Nguyen t~c chungQuy d6i la mot phuang phap bien d6i toan hoc nham dira bai toan ban dAu la

mot h6n hop phirc tap v~ dang dan gian han, qua do lam cho cac phep tinh tro nendang, thuan tien.Khi ap dung phuang phap quy d6i phai twin thu 2 nguyen tic sau :+ Bao toan nguyen t6.+ Bao toan s6 oxi hoa.

2. Cae hurrng quy dBi va chii y(1 ) M9t bai toan co thS co nhieu hu6ng quy d6i khac nhau, trong do eo 3 huang

chinh :Quy d6i h6n hop nhi~u chat v~ h6n hop hai hoac chi mot chat.

Trong tnrong hop nay thay vi gifr nguyen h6n hop cac chat nhu ban dAu, tachuyen thanh h6n hop voi s6 chat it han (cfing cua cac nguyen t6 do), thirong lah6n hop 2 chat, tham chi la 1 chat duy nhat.

Vi du, voi h6n hop cac chat gorn Fe, FeO, Fe304, Fe203 ta co thS chuyen thanhcac t6 hop sau : (Fe va FeO), (Fe va Fe304), (Fe va Fe203), (FeO va Fe304), (FeOva Fe203), (Fe304 va Fe203) hoac re,o,

Quy d6i h6n hop nhiSu chat vS cac nguyen nr tuong irng.Thong thuong ta gap bai toan h6n hop nhieu chat nhung v~ ban chat chi gom

2 (hoac 3) nguyen t6. Do do, co thS quy d6i thang h6n hop dAu vS h6n hop chig6m 2 (hoac 3) chat la cac nguyen nr tuang irng.

Vi du ; (Fe, FeS, FeS2, Cu, CuS, CU2S) gu y d6i) (Cu, Fe, S).Khi thuc hien phep quy d6i phai dam bao :* S6 electron nhirong, nhan la khong d6i (DLBT electron).

* Do sir thay d6i tac nhan oxi hoa ~ co sir thay d6i san pham cho phu hop,Thong thuong ta hay g~p dang bai sau :

Kim loai OXHI) H6n hop san pham trung gian OXH2) San pham cuoiVi du : Qua trinh OXH hoan toan Fe thanh Fe3+

+0Fe -----~---_7

.----t( 1


2/12


6 day, vi trang thai dau (Fe) va trang thai cuoi (Fe3+) 6 hai qua trinh la nhu nhau,ta co thS quy d6i hai tac nhan OXH O2 va RN03 thanh mot tac nhan duy nhftt la O2(2) D? ,,:i~cq~y d6i r:_entrong m9t s6 truOng,h x = 0,025 (2)

2 )t----


3/12


. {x = 0,025 ,{Fe: 0,025molTir (1) v a (2 ) ~ ; V~y X gamy = 0,01 Fe20 : 0,01molTheo bao toan nguyen t6 d6i voi Fe:L :nFe= nFe + 2 nFe2 01 = 0,045 mol ~ m = 56.0,045= 2 ,52 ~ Dap an A

, _ {Fe: x molPhuong a n 2 : Quy dai han hop X thanh FeO: y molTheo bao toan kho i IO 'Q 'ng:56x+72 y = 3,0 (3 )Cac q ua trin h nhuong nhan c ua e le tro n :

x 3x 0,075 0,02 5yTheo ba o toan eletron : 3x + y = 0,075 (4)

{X = 0,015 ,{Fe :0,015 molro (3) (4) ~ ; Vay X gam:y = 0,03' FeO :0,03 mol

Theo bao to an nguyen t6 d6i voi Fe:L:nFe= n-, +nFeO = 0,045 mol ~ m = 56.0,045 = 2 ,52 ~ Dap an A.Vi dy 2 : Hoa tan hoan toan 30,4 gam r~n X g6m ca CuS CU2S va S bing HN03 du , thoa t ra 2 0,1 6 lit khiNO duy nh~t (dkte) va dung dich Y . Them Ba(OH)2 du vao Y thu duoc m gam k t h tua . G ia tri cua m la

A. 81,55 . C. 110 ,95 . D. 115 .85 .. 104,20 .Ghii:

, _ {Cu:x molQui dai han hop X thanh. CuS: y molTheo bao toan khdi luong: 64x+96y= 30,4(5)SO 'd6 hoa bai toan:

{

0X CuCuSo

+2KhiNO(20,16 lit, dktC){ Cuz+Dung dich Y

SO /_ _ + _B _a ("-O _H ",,, )z ,_ d_ u_ . { C +~ :~ Hh

BaS040 ,4 gammgam

Cac q ua trin h n hu ong nh an electronCuS - - - * Cu2 + + S+6 + 8e

x 2 x 8y 2 ,7 - - - * 0,9Theo bao to a n eletron : 2 x +8y = 2 ,7 (6)

----t( 3


4/12


{X = -0,05 { C u : -0,05 molTir (5),(6) => => X g6my = 0,35 C u S : 0,35 mol

, { n C lI ( O H ) = L n C l I = 0,3molTheo bao toan nguyen to: 2nSaS04 = ns = 0,35 mol

=> m = 98.0,3 + 233.0,35 => m=11 0,95 => Dap an CVi du 3: H6n hop X co ti kh6i so voi H2 la 21,2 g6m propan, propen va propin. Khi d6t chay hoan toan0,1 mol X, t6ng khoi IUQng cua CO2 va H20 thu duoc la

A. 18,60 gam.Giai:

B. 18,96 gam. C. 19,32 gam. D. 20,40 gam.

T6ng kh6i hrong CO2 va H20 thu diroc la:M = 44.0,3 +18. (0,06. 4 + 0,042)= 18,96 gam => Dap an B3Tuong tu c o thi quy d6i h6n hop X thanh (C 3H IJ va C3H 6 ) hoac (C3H6 va C3H .) ciing thu duac kit quatrfm

Vi du 4: Nung m gam b9t Cu trong Oxi thu duoc 24,8 gam h6n hQ'P ch:1t r~n X g6m Cu, CuO va CU20.Hoa tan hoan to an X trong HzS04 d~c nong thoat ra 4,48 lit khi SOz duy nh:1t (dktc). Gia tri cua m la

A. 9,6. B.14,72. 0.22,4.. 21,12.Giai:SO ' d b hoa bai to an

CuD un g dich C u2+

K hi S 02(0,2 mol)

, _ { CU: X molQuy d6i h6n hQ'PX thanhCuO: y mol

Theo bao toan kh5i IUQ"ng:64x +80y = 24,8 (9)Cac qua trinh nhuong nhan eletron:Cu ~ cu" + 2e S + 6 2 S + 4 r~ ElLBTe x=0,2 (10)

0,4 0,22x

{X = 0,2 , { C u : 0,2 molTtl' (9) va (10) => ; Yay X gom:y = 0,15' CuO :0,15 mol

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5/12

Phuong phap 7: Cac dang quy dBi

Theo bao toan nguyen t6 d6i voi Cu :I eu = neuo = 0, 2 + 0, 1 5 = 0,35mol = > m = 64. 0,35 = 22 ,4 = > Dap an D~Tuong tu co thi quy d6i h6n h9'PX thanh (Cu va CU20) hoac (CuO va CU20)2. Quy dBi nhi~u hop eht v~ cac nguyen til' ho~e don eht nrong tfogVi du 5: (Lam lai vi du 1) Nung m gam b(>t s~t trong oxi, thu duoc 3,0 gam h6n hop c hA t r~ X. Hoa tanht h6n hop X trong dung dich HN03 (du), thoat ra 0,56 lit (0 dktc) NO (la san pham khir duy nhAt) . Giatri cua m la

A. 2 ,52 . D.2 ,32 ..2 ,2 2 . C .2 ,62 .Giai:

, _ {Fe: x molQuy doi hon hop X thanh:O:ymol

Sa d6 hoa bai toan :

Theo bao toan kh6i luong: 56x + 1 6y = 3,0 (1 1)Cac qua trinh nhiro ng nh~n electron:Fe ~ Fe +3 + 3e ; 0 + 2 e ~ 0.2 ; N+ S + 3e ~ N+2X 3x y 2 y 0,075 0,02 5

{X = 0,045 {Fe: 0,045 molTir (11) va ( 1 2 ) = > ; Yay X g6my = 0,03' Cu :0,03 mol

m = 56.0,045 = 2 ,52 ~ Dap an A .Vi d\l 6: Tron 5,6 gam b(>t m ~t voi 2 ,4 gam b(>t hr u huynh r6i du n nong ( tro ng di~u kien khong cokhongkhi) th u diroc h6 n hop r~ n M. Cho M tac dung voi hrong du dung dich H Cl thAy giai phong h6n h9P khfX va con lai m (>t phan khong tan Y . D~ d6t chay hoan toan X va Y ccln vua du V lit khf oxi (dktc) . Gia tricua Via

A. 2 ,8. B.3 ,36. 0.3,08.. 4 ,48.Giai:Nhan thAy: H6n hop khi X g6m H2S va H2 , phcln khong tan Y la SH6n hop H2 va H2S co th~ quy d6i thanh H2 va S, nhu v~y d6t X va Y coi nhir d6t H2 va S, vi v~y s6 molH2 bang s6 mol Fe2H2 + O2 ~ 2H20

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6/12

Phuong phap 7: Cac dang quy dA i

S + O2 ~ S02~ Y o = ClnFe+ns).2 2,4= 2 ,8lft

2 2~ Dap an A.Vi d l} 7: (Lam 19i vi du 2) Hoa tan hoan toan 30,4 gam rin X g6m Cu, CuS, CU2Sva S bang HN03 du,tho at ra 20,16 1ftkhi NO duy nhih (dktc) va dung djch Y. Them Ba(OHh du vao Y thu ducc m gam k~ttua, Gia tri cua m la

A. 81,55. B.I04,20. D. 115,85.. 110,95.Giili:Quy o b i h6n hop X thanh{Cll:X molS:ymol

Theo bao toan kh6i hrong: 64x + 32y =30,4 (13)SO ' d6 hoa bai toan:

KhfOO(20,16 lit, dktc)

Dungdich Y {CU2+ _ + B _ a C . : _ O _ ; H ) : . . ; _ 2 d_\f_~ I {sot

+2Cu(OHh+6BaS04

mgam

Cac qua trinh nhuong, nhan electron:CuO ~ Cu+2 + 2e; s ~ S +6 + 6ex 2x 6y 2,7 f- 0,9Theo bao toan electron:2x+6y =2,7 (14)

{X = 03TLI'(13),(14) ~ , ~y = 0,35 {

Cll :0,3 m olXg6m S :0,35 m olTheo bao toan nguyen t6:

{nCU(OHh =ne u =0,3molnB aS04 = n s = 0,35mol~ m = 98.0,3 + 233.0,35~ m= 110,95~ Dap an c.

6 ) r - - - - - - - - - - - - - - - - -


7/12

Phuong phap 7: Cac dang quy dA i1- . _

Vi d1}.8: (Lam lai vi du 3) H6n hop X co ti khdi so voi Hz la 21,2 gom propan, propen va propin. Khi d6tchay hoan toan 0,1 mol X. tong kh6i IUQ'ng cua COz va HzO thu duoc laA. 18,60 gam. B. 18,96 gam. C. 19,32 gam.

, _ {C: 0,3 molQuy dai han hop X thanh = > 4 24 3 12 64 Ir- H I nH =, -,. =, rn a:ymoD. 20,40 gam.

SO'd 6 c ha y:

T6ng khoi hrong COz va HzO thu duoc la: m= 44. 0,3 + 18. 0,32 = 18,96 gam= > Dap an B.Vi du 9: (Lam lai vi du 4) Nung m gam bet Cu trong oxi thu duoc 24,8 gam h6n hop chat r~n X gom Cu,CuO va CUzO . Hoa tan hoan toan X trong HzS04 d~c nong thoat ra 4,48 lit khi SOz duy nh~t (dktc), Giatrj cua m laA.9,6 C.21,12. 0.22,4..14,72.

Giai:, _ {Cu:xmOIQuy dai han hop X thanh O:y mol

Thea baa toan khdi IUQ'ng: 64x + 16y =24,8 (15)SO' d6 hoa bai toan :

S02Cu _ + , - , - , [O , - , - l _ _ ~ X {Cou } H1S 0 4 d _ _ _ _ _ . (0,2 mol)

~{CU2+02-24,8 gamgam

Cac qua trlnh nhuong, nhan electron:Cu ~ Cu +2 + 2e; 0 + 2e ~ O'"; S+6 + 2e ~ S+4x 2x Y 0,2y 0,4Thea baa toan electron: x - y =0,2 (16)

{X = 035Tir (15),( 16) = > 'y = 0,15

{cu :0,35 molV~yX go m 0 :0,15 mol= > m= 64.0,35 =22,4

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8/12

Phuong phap 7: Cac dang quy diH

=> Dap an D.3. Quy d6i mQt eh~t thanh nhi~u eh~t.Vi du 10: Khi d6t chay hoan toan mot polime X (tao thanh tir phan irng d6ng trung hop gitra buta-l,3-dien va acrilo nitrin) voi luong oxi vira du thay tao thanh mdt h6n hop khi o ' nong dQ ap su~t xac dinhchua 59,1 % CO2 v~ th~ tinh, Ti I~ s6 mol hai loai monome la

B.~3 D.~2Giai:Quy dbi polime thanh 2 monome ban d~u

x 4x 3x

y 3y 0,5y,5yTa co:4x + 3y = 0,591 => ~ = . . ! _ =>7x+5y y 34. Quy d6i hie nhan oxi hoaVi du l l : (Lam lai vi du l ) Nung m gam bQts~t trong oxi, thu duoc 3,0 gam h6n hop eh~t r~n X. Hoa tanh~t h6n hop X trong dung dich HN03 (du), thoat ra 0,56 lit (dktc) NO (la san pham khir duy nhat). Gia tricua m la:

A.2,52 B. 2,22 C. 2,62 D.2,32Giai:So' d6 hoa bai toan:

Fe +[0]FeFeO NOX dd HN03 (0,025 mol)Fe203 dd Fe3+Fe3043,0 gamgam

Thay vai tro oxi hoa cua HN03 bang [0], ta co:

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9/12


Fe+[0] FeO +[0]Fe X Fe203(.) Fe203 ( . . )

Fe304m gam 3 gama oay ta oil thay vai tro nhan electron cua N+ 5 bang 0:

0,075 0,025Theo nguyen t~c guy obi, s6 electron do N+ 5 nhan va 0 nhan phai nhu nhau:=> 2nO(**)= 0,075=> nO() = 0,0375Theo b ao toa n khoi hro ng: mFe,O , = mx + mO( ) = 3,0 + 16.0,0375 = 3,6 gam

, , 2 .3,6 0045 ITheo bao toan nguyen to doi voi Fe: nFe= 2 n Fe ,O , = 160 = , mo=> m = 56.0,045 = 2 ,52 gam=> Dap an A.Vi d\l 12: (Lam lai vi du 4) Nung m gam bot Cu trong oxi thu duoc 24,8 gam h6n hop chat r~n X g6mCu, CuO va CU20. Hoa tan hoan toan X trong H 2S0 4 O ? C n6ng thoat ra 4,48 lit khi S02 duy nh~t (dktc) ,G ia tr i cua m la

A. 9,6 C. 2 1 , 1 2 . 0.22,4.. 14 ,72.Ghii:S o ' 06 h6a ba i toan:

Cu _+-, -[O-- ,- ]_ ~ X {~~OCu 202 4,8 gam

Dung dich Cu2+

Khi SOz(0,2 mol)

mgamThay vai tro oxi h6a cua H 2S0 4 bang [0]:

CU _ _ _ _ _ ;+ = [O ! . . _ .] ~ X{~~O } _ _ _ __ ;+ = [O ! . . . . _ ] ~ CuO(.) ( . . )

Cu20m gam 24,8 gama oay ta thay vai tro nhan electron cua S+6 bang 0:

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10/12

Phirong phap 7: Cac dang quy o B i

0,4 0,2Thea nguyen t~c guy d6i: nO()=0,2 mol.Thea baa toan kh6i IU911g:mCuo=mx + mO(") = 24,8 + 16.0,2 =28 gam= > m = 28 .64 = 22 480 '= > Dap anD.

III. BAIT!P TV LUY~NCall 1 : D@hoa tan hoan toan 2,32 gam h6n hQ'Pg6m FeO, Fe304 va Fe203 (trong do s6 mol FeO bang s6mol Fe203) dn dung vira du V lit dung dich HCIIM. Gia tri cua ViaA. 0,08. B.O,16. C. 0,18. D.0,23.

Call 2 : Cho 11,36 gam h6n hQ'Pg6m Fe, FeO, Fe203 va Fe304 Phan irng h~t voi dung dich HN03 loang(dir), thu duoc 1,344 lit khi NO (san phd rn khir duy nhat a dktc) va dung dich X. Co can dung dich X thudiroc m gam mu6i khan G ia tri cua m laA. 49,09. B.38,72. C. 35,50. D.34,36.

Call 3: Oxi hoa cham m gam Fe ngoai khong khi thu diroc 12 gam h6n hop X g6m FeO, Fe304 Fe203 vaFe du, Hoa tan hoan toan X trong HN03 thu duoc 2,24 lit NO (chAt khir duy nhAt, do a dktc) . Gia tri m laA. 7,57. B.7,75. C. 10,08. D.IO,80.

Call 4 : D6t chay 6,72 gam bot Fe trong khong khi dir diroc m gam h6n hQ'PX g6m FeO, Fe304 Fe203 vaFe dir. D@hoa tan X cdn dung vira h~t 255ml dung dich chua HN03 2M thu diroc V lit khi N02 (Sanp ham k hir duy nhAt, do a dktc) . G ia tri cua m , V lfin hro t laA. 8,4 va 3,360.C. 10,08 va 3,360.

B. 8,4 va 5,712.D. 10,08 va 5,712.

Call 5 : H6n hQ'PX g6m Mg, MgS va S. Hoa tan ho an to an m gam X trong HN03 d~c, nong thu duoc2,912 lit khi N2 duy nhAt (dktc) va dung dich Y. Them Ba(OH)2 du vao Y duoc 46,55 gam kSt tua. Gia tricua m laA. 4,8. B.7,2. C.9,6. D.12,0.

Call 6 : Cho 18,5 gam h6n hop g6m Fe va Fe304 VaG 200ml HN03 dun nong. Sau phan irng thu diroc2,24 lit khi NO duy nhAt (dktc), dung dich X va con lai 1,46 gam kim loai chua tan. N6ng dOmol cuadung dich HN03 da dung laA. 2,7M. B.3,2M. C. 3,5M. D.2,9M.

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11/12

Phuong phap 7: Cac dang quy ( f A i

Cflu 7 : Hoa tan hoan toan m gam h6n hQ'PX g6m Fe, FeCIz , FeCh trong H2S04 d~c nong, thoat ra4,48 lit khi S02 duy nhfit (dktc) va dung dich Y . Them NH3du vao Y thu duoc 32,1 gam kt tua. Gia trim laA. 16,8. B. 17,75. C. 25,675. D.34,55.

Cau 8 : Hoa tan hoan toan 34,8 gam mot oxit s~t dang Fe.O, trong dung dich H2S04 d~c nong, Sau phanirng thu duoc 1,68 lit khi S02 (san pham khir duy nhfit do o dktc), Oxit Fe.O, laA . FeO. B. Fe304 C. FeO hoac Fe304 D. Fe203

Cau 9 : Hoa tan hoan toan 25,6 gam chat r~n X g6m Fe , FeS, FeS2 va S bang dung dich HN03 du, dktcra V lit khi NO duy nhfit (dktc) va dung dich Y . Them Ba(OHh du vao Y thu duoc 126,25 gam kt tua.Gia tri cua V laA. 17,92. C.24,64. D.27,58..19,04.

Cau 10 : Cho h6n hop X g6m FeO, Fe203 , Fe304 voi s6 mol bang nhau. Lfiy a gam X cho phan irng voiCO nung nong sau phan irng trong binh con la i 16,8 lit h6n ho p r~n Y. Hoa tan hoan toan Y trong H2S04dac, nong thu duoc 3,36 lit khl S02 duy nhfit (dktc). Gia tri cu a a va s6 mol H2S04 da phan ung I~n hrot laA . 19,20 va 0,87.C. 18,56 va 0,87.

B. 19,20 va 0,51.D. 18,56 v a 0,51.

Cau 11 : H6n hQ'PX co ti kh6i so voi H2 la 27,8 g6m butan, metylxiclopropan, but-2-en, etylaxetilen vadivinyl, Khi d6t chay hoan toan 0,15 mol X, t6ng kh6i luong cua CO2 va H20 thu duoc laA. 34,50 gam. C. 37,20 gam. D. 39,90 gam.. 36,66 gam.Cau 12 : Hoa tan hoan toan 14,52 gam h6n hQ'PX g6m NaHC03 , KHC03 va MgC03 trong dung dich

HCI du, thu diroc 3,36 lit khi CO2 (dktc), Kh6i luong muoi KCI tao thanh trong dung dich sau phan irnglaA. 8,94 gam. B. 16, 7 gam. C. 7,92 gam. D. 12,0 gam.

Cau 13 : Cho 13,92 gam h6n hQ'PX g6m Cu va mot oxit s~t vao dung dich HN03 loang du thu duoc2,688 lit khi NO (san pham khir duy nhat, do a dktc). Co can dung dich sau phan irng thu duoc 42,72 gamrnuoi khan. Cong thirc cua oxit s~t laA.FeO.

Cau 14 : Cho 9,12 gam h6n hop g6m FeO, Fe203, Fe304 tac dung voi dung dich HCI (du). Sau khi cacphan irng xay ra hoan toan, duoc dung dich Y ; co can Y thu duoc 7,62 gam FeCIz va m gam FeCI3 . Giatri cua m laA. 4,875 . D.4,80..9,60. C. 9,75.

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Phuong phap 7: Cac d,ng quy c 1 6 i

1A8B

2B9C

3CIOD

f l A P A N '4A1 1B

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5C12A

6B13A

7D14C

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PP7-Cac Dang Quy Doi