J, U thuyet van dung va phuong phap gial
1. L i thuyet van dung va phuong phap giai
Cacbon chay duoc trong khdng khi, phan iJng toa nhi^u nhifit:
0 ,0 +4
C + O2 C O 2
CJ nhifet d6 cao, cacbon lai khir duoc CO, theo phan ling:
44 0 n +2 C O 2 + C —!—> 2 C O
d nhi^t d6 cao, cacbon c6 thd' khix duoc nhilu oxit, phan ling v6i nhi^u chat 0x1 hoa khac nhu HNO,, H,S04 dac, KC10„ ...
Thi'du: C + 4HN0,(dac) — ^ C O 2 + 4 N O 2 + 2 H 2 O 0 ,0 +2
C + ZnO — ^ Zn + CO
6 nhiet d6 cao c6 chat xuc tac, C tac dung v6i khi H , tao thanh khi CH4:
C + 2H2 ' > C H 4
d nhidt d6 cao, C tac dung duoc voi m6t s6' kim loai tao thanh cachua kim loai
0 ,0 - 4
Thidu: 4A1 + 3 C — ! — > A I 4 C 3
Nh6m cacbua 276
C t y TNHHMTV DWHKhattg Viit
Cacbon tac dung duoc v6i hoi nu6c 6 nhidt d6 cao tao thanh khi than udt C O , C O , va H , . giam s6' dn, ta dat s6' mol C O , C O , tao thanh, con s6' mol H , tinh duoc theo s6' mol cua C O , C O , .
CO kh6ng tac dung vdi nudc, axit va dung dich kiem 6 di^u kien thucmg.
Khi d6't nong, khi C O chay trong oxi hoac trong khdng khi, cho ngon lua mau lam nhat va toa nhi6u nhidt:
+2 0 +4 2 C O + O2 ~ — > 2 C O 2 nhiet d6 cao, khi C O khir duoc nhidu oxi kim loai.
+2 0 +4 Thidu: Fe203 + 3 C O ——> 2Fe + 3 C O 2
Tinh chat nay duoc diing trong luy€n kim de khu cac oxit kim loai. K h i C O khir duoc cac oxit kim loai sau kem.
Phuong phap su dung dfe' giai cac bai tap dang nay:
. Phuong phap bao toan electron.
. Phuong phap quy doi.
• Phuong phap bao toan khoi luong.
2. Cac thi du minh hoa:
Thidu I: H6n hop X gom FeO, Fe^O, va Fe304. Cho khi C O qua m gam X nung nong, sau m6t then gian thu duoc h6n hop chat ran Y va h6n hop khi Z. Cho toan bo Z vao dung dich Ca(OH), du, den phan ihig hoan toan, thu duoc 4 gam ke't tiia. Mat khac, hoa tan hoan toan Y trong dung djch H,S04 dac, nong (du), thu duoc 1,008 lit khi S O , (dktc, san ph^m khir duy nhat) va dung dich chua 18 gam mu6'i. G i a trj ciia m la
A. 6,80 B. 7,12 C . 13,52 D. 5,68
(Trich de thi tuyen sinh DH khoi B nam 2013) Hu&ng dan giai
De }>idi hai tap nay c6 thi suT Jung phucfng phap quy dSi nguyen ti(, phuong phap hiio toan nguyen to (nguyen to sat) vd phifcfng phap hdo toan electron de nhanh chong lap diMc cacphirang tiinh dai so.
Ke't tiia la CaCOj: ncaco, = 0-04 (mol) 18
Mu6-i la Fe3(S04)3: " ^ ^ ^ ( 5 0 4 ) 3 = ^ = 0-045 (mol) 1 008
, S6' mol khi SO,: n^^ = = 0,045 (mol)
' 22,4 P T H H: CO, + Ca(OH), ^ CaCOji + H , 0
0,04 <-0,04 ' . ; t - A 4
•uy d6i h6n hop X thanh Fe (x mol) va O (y mol). ' ' •
V i nguyen t6' sSt duoc bao loan nfin: x = np^pg2(so4) ) 2 . 0 , 0 4 5 = 0,09(mol) Cac qua trinh nhucmg - nhan electron:
-2 Fe - 3e -> Fe*^ O + 2e ^ O 0,09 -^O,n(,mo\) y ^ 2y
C - 2e C S + 2e ^ S
• ' ' 0,08 < - 0,04 0,09 < - 0,045 Theo djnh luSt bao toan electron ta c6:
0,27 + 0,08 = 2y + 0,09 =^y = 0,13 V Vay m = mp, + mo = 0,09 . 56 + 0,13 . 16 = 7,12 (gam)
Dap an dung la B.
Thidu 2: DSn lu6ng khi CO di qua h6n hop gom CuO va FcjOj nung nong, sau mdt then gian thu duoc chat ran X va khi Y. Cho Y ha'p thu hoan to^n vao dung dich BaCOH), du, thu duoc 29,55 gam k6t tua. Chat ran X phan iJng vdi dung djch HNO, du thu duoc V lit khi NO (san p h ^ khu duy nhaft, d dktc).
Gia trj cua V la
A. 2,24. B.4,48. C. 6,72. D. 3,36.
(Trich dethi tuyen sink DH khoi B) Hu&ng dan gidi
K6t tua m BaCOj =>nBaco3 =0-15 (mol) Ta cd: nco = n^o^ = n^coj, = 0.15 (mol)
+2 +4 +5 +2 • C - > C + 2e N + 3 e ^ N
0,15-). 0,3 0,3 ^ 0,1 Vay V - 0 , 1 . 2 2 , 4 - 2 , 2 4 ( 1 )
Dap an dung la A.
Thi du 3: Cho mdt ludng khi CO di qua 6'ng siJ dung m gam FejOj nung nong Sau mdt thdi gian thu duoc 10,44 gam chat ran X gdm Fe, FeO, FeiO, va Fe304. Hda tan hd't X trong dung dich HNO3 dac, ndng thu dugc 4,368 lit NO2 (san phdm khu duy nha't d di^u kidn chuin). Gia tri ciia m la
A. 12 B. 24 C.10,8 D. 16
(Trich di thi du bi dai hocl Hu&ng ddn gidi
De gidi nhanh hai nay nen quy doi hSn hap sat vd cdc oxit cua sat thdnh Fe FcpO, (nen chgn FfjO, v; viet phuang trinh hod hoc dan gian nhd't).
Ta cd hd:
Xheobaira: nN02 = ^ | ^ = 0,195(mol)
Ta quy hdn hop X thanh 2 chat: Fe, FezOa ' - Fe + 6HNO3 ^ Fe(N03)3 + 3NO2 + 3H2O
x / 3 X
Fe203 + 6HNO3 ^ 2Fe{N03), + 3H2O y
5 6 x / 3 + 160y = 10,44
X = 0,195 ^
Gm ra ta duoc: x = 0,195; y = 0,0425 Fe203 + 3CO - > 2Fe + 3CO2 x / 6 < - x / 3
Vay m = ( x / 6 + y).160 = (0,195/6 + 0,0425).160 = 12(g) Dap an diing la A.
Thidti 4: Cho hoi nude di qua than ndng do, thu duoc 15,68 lit hdn hop khi X (dktc) gdm CO, CO, va H,. Cho toan bo X tac dung he't vdi CuO (du) nung ndng, thu duoc hdn hop chat ran Y. Hoa tan toan bd Y bang dung dich HNO3 (loang, du) duoc 8,96 lit NO (san ph&n khir duy nha't, d dktc). PhSn tram th^
t i c h k h i C O t r o n g X l a
A. 28,57%. B. 14,28%. C. 18,42%. D. 57,15%.
(Trich de tuyen sinh Dai hoc khoi B) Hu&ng ddn gidi
15 68 8 96
Theob^ira: Ux = ^ j j = 0,7(mol); n^o = ^ - 0 , 4 ( m o l ) H20 + C ^ C O + H2 2H20 + C - > C 0 2 + 2 H 2
x - > x ( m o l ) y - > 2 y ( m o l ) Tacd: x + y + x + 2 y = 0 , 7 =>2x + 3y = 0,7 ( l )
CO + CuO ^ Cu + CO2
x xmol x + 2y - > ( x + 2y)mol 3Cu + 8HNO3 -> 3Cu (NO3 )^ + 2NO + 4H2O
2x + 2y - > 4(x + y ) / 3 ,
Tacd: 4(x + y ) / 3 = 0,4 =>x + y = 0,3 (2) ; H2 + C u O ^ C u + H2O
0 7 Q
x = 0 , 2 ; y = 0 , l x.100%
0,7
0,2.100%
0,7
= 28,57%
Tir (1,2)
Vay %Vco/x=%nco/x = Dap an diing la A.
Thi du 5: Cho V lit h6n hop khi (o dktc) g6m CO va phan ixng vdi mOt lirgng du h6n hop ran g6m CuO va Fe304 nung nong. Sau khi cac phan urng xay ra hokn toan, kh6'i luong h6n hop rdn giam 0,32 gam. Gia tri ciia V la
A. 0,560. B. 0,224. C. 0,112. D. 0,448.
(Trich De thi tuyen sinh DH • CD khoJAj Huong ddn gidi
CO, (k) -> H2O (h) So 66 phan ung: CO + [O]
H, + [ 0 ]
Kh6'i luong h6n hop rSn giam chinh bSng kh6'i luong nguy^n t6' oxi trong oxit bi CO, H , chie'm. Suy ra: nio, = — = 0,02(mol).
16 vay V = 0,02. 22,4 = 0,448 (lit).
Dap an diing la D.
Thi du 6: Cho lu6ng khf CO (du) di qua 9,1 gam h6n hop CuO va AUO, nung nong de'n khi phan dug hoan toan, thu duoc 8,3 gam chat rSn. Kh6'i luong CuO C O trong h6n hop ban dSu la
A. 0,8 gam. B. 8,3 gam. C. 2,0 gam. D. 4,0 gam.
(Trich De thi tuyen sinh Dai hoc khoi A) Ha&ng ddn gidi
CO„„) + CuO„, '—^ Cu„, + C O , t -> kh6ng xay ra
PTPLT xay ra:
CO +A U O 3 , , ,
Khi 1 mol CuO (80g) phan ung thi kh6'i luong giam 16 gam.
vay khi khd'i luong oxit giam 9,1 - 8,3 = 0,8 gam thi s6' mol CuO da phan ung bang 0,05 (mol).
vay m c u O( b a n d i u ) = m c u O ( p / * ) = 0,05. 80 = 4(gam).
Dap an diing la D.
Thidu 7: Cho khi CO (du) di qua 6'ng su nung nong dung h6n hop X g6m A I 2 O 3 .
MgO, Fe304, CuO thu duoc chat ran Y. Cho Y v^o dung djch NaOH (du).
khua'y k i , tha'y con lai phSn kh6ng tan Z. Gia sir cac phan ling xay ra hoan toan. Vhin kh6ng tan Z g6m
A. Mg, Fe, Cu. B. MgO, Fe304, Cu.
C. MgO, Fe, Cu. D. Mg, A l , Fe, Cu.
(Trich De thi tuyen sinh Cao dang khoi A t
CO + AUOj CO + MgO 4CO + Fe304 '
Hu&ng ddn gidi kh6ng xay ra
,0
-> kh6ng xay ra
^ 3Fe + 4CO, CO + C u O .0 -> Cu + CO, Y g6m AUO,, MgO, Fe, Cu.
A U O 3 + 2NaOH + 3H,0 > 2Na[Al(OH)4]
MgO, Fe, Cu khdng tac dung voi NaOH.
vay Z g6m MgO, Fe, Cu.
Dap an diing la C.
fhi^du 8: Cho 4,48 lit khf CO (o dktc) tir tir di qua 6'ng su: nung nong dung 8 gam m6t oxit sat den khi phan utig xay ra hoan toan. K h i thu dugfc sau phan umg C O ti kh6'i so vdri hidro bang 20. C6ng thUc ciia oxit sat va phSn tram th^
tich ciia khi CO, trong h6n hop khf sau phan umg (cho H = 1; C = 12; O = 16;
Fe = 56) '
A.Fe,04;75%. B. FeO; 75%. C. F e A ; 75%. D. F e A ; 65%.
(Trich De thi tuyen sinh Cao dang khoi A) Hu&ng ddn gidi
xFe yCO, 4,48
Theo bai ra: nco = — — = 0,2 (mol) ! 22,4
Phuong trinh phan limg: yCO + Fefiy -
Ta tha'y: no, = no, 3 => "hh kh, = 0,2 (mol)
=^ m,h,h,- = 0 , 2 . 2 0 . 2 = 8(gam)
Theo dinh luat bao toan khoi luong: m^Q + "^Pe^Oy = " ^ F e + "^002
=^mp, = 0,2. 28 + 8 - 8 = 56 (gam) = > n F e = ^ = 0,1 (mol) 56 - 2^ 9 0- ^ ^ ^ - 0 . 1 5 (mol)
16
% X : y = 0,1 : 0,15 = 2 : 3. vay oxit la Fe^O,.
Goi a, b Idn luot la so mo! CO, CO, trong h6n hop khf sau phan umg.
x + y = 0,2 Taco: I
28x + 44y = 20.2.0,2 = 8 ay %V(CO,) = 0,15. ^ = 75%.
ip an dung la C.
-x=0,05; y = 0,15
Kt thuatmm ^Vn: tiiiann ni noa tiyi., iiff> J. -
Thi du 9: Ddn tir tir V lit khi CO (6 dktc) di qua mot 6ng sii dung lucôig duli^jP hop ran g6m CuO, Fe^O, (6 nhiet d6 cao). Sau khi cac phan umg xay ra hoan toan, thu duoc khi X. DSn toan b6 khi X a tren vao luong du dung djch Ca(OH), thi tao thanh 4 gam k€l tia. Gia trj cua V la
A. 1,120. B. 0,896. C. 0,448. D. 0,224.
(Trich De thi tuyen sink Cao dang kh^) Hu&ng ddn gidi
Theo bai ra: n^^^o^ " " [ ^ " 0,04(mol) ^, ^^.^
CO )C02 ^'•'""'2 ) C a C 0 3 i
0,04 (mol) 0,04 (mol) ' '
=>nco ==ncaco3 =0,04(mol) Vco = 0,04.22,4 = 0,896(1).
Dap an diing la B.
3. Cac bai tap tir luyen: