Cau 23: D6't m6t mlu than chi chiia tap chat luu huynh trong oxi. Cho h6n hop khi
3. Tac hai cua nurdc cumg ^,
• Xa phong khong giat giQ duoc trong nude cumg.
Diing nude cumg de na'u thiic an, se lam cho thirc p h ^ lau ehfn va giam mui vj.
- Tao ra can trong ndi hoi, gay lang phf nhien lieu khdng an toan.
Gay ra hien tuong lam tac dng dSn nude nong trong san xua't v^ trong ddi sd'ng.
Lam hong nhi^u dung dieh c^n pha ehe'.
**• Cach lam mem nude cumg
t^guyen tac: La giam ndng dd eae cation Ca-\ trong nude cdmg.
Thuc hien:
Chuyen nhCrng cation nay thanh hop chat khdng tan (phuong phap ke't tiia).
Thay the nhOmg cation nay bang nhOng cation khac (phuong phap trao ddi ion).
^ N H O M
^'^Tinh chat vat li
Nhdm la kim loai m^u trang bac, nhe (d = 2,7g/em'). Nhdm dSn dien td't, m^m deo (de keo sgi va dat mong).
2. Tinh chat hoa hoc
- Nh6m la k i m loai c6 tinh khijf manh (tuy nhidn tinh khi^ ciia A l yfi'u hcfn cAc kim loai ki^m va kifim th6).
- Cac d6 vat bang nh6m b^n a 6'\iu kifin thuomg vi nh6m c6 Idp mang oxit rfe't mong, b^n bao v6 (khi nh6m tao h6n hS'ng vdi thiiy ngan, tinh lifin tuc cua l6p oxit bj pha v6, nh6m tac dung manh vdi oxi).
a. Tac dung vdi phi k i m
2A1 + 3 0 1 , > 2AICI3 4Al(b^,) + 3O2 > 2AI2O3 2A1 + 3S — ^ A1,S3 b. Tac dung vdri axit
* Dung djch axit HCl, H2SO4 loang:
2A1 + 6H* > + 3H2T
* Dung dich H2SO4 dac, nong: * 2A1 + H2SC4 — ^ A1:(S04)3 + SOjT + 6H2O
Chu y; Nh6m bj thu d6ng hoa trong H2SO4 dac, ngu6i.
* Dung djch HNO3:
A l + HN03„„a„gho^d,c.„6„g) > A1(N03)3 + N, 0 , + H2O A l + HNO3 (1) > A K N O j ) , + NH4NO3 + H2O
San phdm tao thanh c6 th^ c6 m6t h6n hop san ph^m khiif, khi do ling vdi m6i san p h i m khix, ta vifi't mdt phuong trinh hoa hoc.
Thi' du, nhdm tac dung vdi axit nitric thu diroc hdn hop san phim khix chda N^O va NO, thi ta vie't thanh hai PTHH nhu sau:
8A1 + 3OHNO3 > 8AI(N03)3 + 3N20t + ISH^O A l + 4HNO3 > A1(N03)3 + N O t + 2H2O
Chu y; K i m loai A l khong tan trong HNO3 dac, ngu6i (do hifin tuong thu ddng hoa).
c. Tac dung vdi HiO
2AI + 6H2O >. 2AI(OH)3i +3H2
Phan ling nay chi xay ra d b^ mat ciia kim loai nhdm do A1(0H)3 ^ ^ barn chic, bao
\t kim loai nhdm ban trong. Thuc td'coi nhdm khdng tac dung vdi HjO!
d. Tac dung vdi dung djch ki6m
2A1 + 2NaOH + 6H2O > 2Na[Al(OH)4] + 3H2t 2A1 + Ca(OH)2 + 6H2O > Ca[Al(OH)4]2 + SH,
Chu v: A l khdng tan trong dung djch NH4OH (dung djch NH3, ki^m ydu).
302
ac dung vdi oxit kim loai (phan ung nhidt nhdm) 2A1 + Fe^Oj '° ) 2Fe + A l j O ,
2A1 + 0-203 — ^ 2Cr + AI2O3 ' " • ' pTTQ: 2yAl,„ + 3 M, 0 , „ , >^ 3xM(,, + yA^O,,,,
t Trong phan litig nhidt nhdm, cac chSt tnrdc va sau phan ling d^u la cac ch^t ran (cac kim loai va oxit k i m loai). Do dd: m^^,^^^^ = m^^^^„.
3 San xuat nhom
Quang boxit sach -sOz-FezOg ^ (nguyfin chat) 2AI2O3 'ằP"c.960ôc ^ 4 A U 3 o^ t
cnolit
Khi O2 sinh ra ddt chay cue duong (lam bang than chi):
C + O2 > CO2
* Vai trd ciia criolit (Na3AlF5): , + Tia't kiem nang luong (lam giam nhifet dd ndng chay ciia nhdm oxit tic
2050''C xudng khoang 960°C).
+ Tao ra chat long cd tinh dSn didn tot hon AI2O3 nguydn chat ndng chay.
+ Tao ra chat long nhe hon nhdm long, n6i I6n tr6n va ngan can A l ndng chay khdng bj oxi hoa trong khdng khi.
Chu v: Sir khir A P* trong AUO, rat khd khan, khdng the khiJf dupe b^ng cac chat khu thdng thudng nhu C, CO, H2,...
4. Mot so hop chat quan trong cua nhom a. Nhdm oxit, AI2O3
• Rft b^n n h i a va khd bj khir thanh kim loai A l . , - C6 tinh chat ludng tfnh:
# Al203 + 6Ua > 2AICI3 + 3H2O.
AI2O3 + 2NaOH + 3H2O > 2Na[Al(OH)4]
•'^ Nhdm hidroxit, Al(OH)3 K^mben vdi nhiat:
2Al(OH)3 — ^ AI2O3 + 3H3O Co tfnh chat ludng tfnh:
Al(OH)3+3HCl )-AlCl3 + 3H20
Al(OH)3 + NaOH > Na[Al(OH)4] =' natri aluminat
' Nhdmsunfat ' •
^ e n chua: K2SO4. Al2(S04)3. 24H2O.
fn nhdm: M2SO4. Al2(S04)3. 24H2O ( M la Na*, L i * , N H 4 ) .
303
C/lM v.-
+ Cach nhan biet ion A l ' * trong dung dich: Cho tir tir dung dich NaOH dd'n du vao dung dich thi nghiem, n6'u tha'y c6 kd't tiia keo xua't hidn r6i tan trong NaOj^
du dung djch c6 ion A l ' * :
A l ' * + 3 0 H - > Al(OH)3 i (keo, trang) Al(OH)3 + NaOH,<i„) > Na[Al(OH)4] (tan)
+ Cho NajCOj, NajS, ... vao dung djch mu6'i nh6ni c6 k^t tiia va c6 khi bay le^:
2A1'* + SNa^COj + S H P > 2 A l ( O H) 3 i + SCO^T + 6Na*
2A1'* + 3Na,S + 6H3O > 2Al(OH)3 i + 3 ^ 8 1 + 6Na*
+ Cho dung dich N H , tac dung vdi dung dich mu6'i nh6m A l ' * , chi thu duoc ket t i a Al(OH)3 (ket tiia khong bj tan trong N H 3 du):
3 N H 3 + 3 H P + A l ' * > Al(OH)3 i + 3 N H ;
B. C A C D A N G B A I T A P T R O N G T H I T U Y ^ N S I N K D H - C D Dang 1: Bdi tap xdc dinh kim loai (lA, IIA, Al) 1. L i thuyet van dung va phuong phap giai:
* Di giai cac bai tap dang nay c6 th^ sir dung cac phuong phap giai nhanh:
- Phuong phap xac dinh chat dua vao cong thurc tinh phan tu khoi: Gia sir c6 chat cho electron la A . Ta c6:
A > A"* + ke Vay: • " A 1 ằ* r n ^ k
M A ^ ' ^c(cho)
+ Dua vao cac dO ki^n bai ra cho, xac djnh duoc cac dai luong m^, k, n^^M•
+ Ti'nh gia trj nguydn tir khd'i M A .
+ Tir nguydn tir kh6'i xac djnh duoc kim loai cSn tim.
Phuong phap trung binh: C6ng thuc tinh nguySn tu kh6'i trung binh cua hai
— m hh kim loai li6n tid'p trong ciing m6t nhom A : M =
" h h + Tinh cac luong chat da cho trong bai ra.
+ Viet phuong trinh hoa hoc (so 66 hoa hoc) sir dung k i hidu trung binh.
+ Tinh nguyen tir khoi trung binh, suy ra hai kim loai cin tim.
Phuong phap bao toan electron: Trong phan ihig oxi hoa khu, t6ng s6'm"^' electron do chat khif cho phai dung bang t6ng s6' mol electron do chat oxi hf-' nhan: I e (cho) = E e (nhan) => n,h„. Necho = n„h>n-
Viet cac qua trinh oxi hod, qua trinh khiJr (khdng cin vie't phuong trinh phan oxi hoa - khu).
+ Dat in, dua vao djnh luat bao toan electron lap duoc phuong trinh dai s6.
+ Giai he phuong trinh, xac djnh duoc nguyen tu khd'i M => K i m loai c5n tim.
phuofng phap bao toan khoi luong: Trong m6t phan ling hoa hoc, t6ng khd'i luong cua cac chSit san p h ^ bang t6ng kh6'i luong ctia cac chait tham gia phan ling.
yVp dung: Trong m6t phan limg, c6 n chat (ke' ca chalt phan ling va san p h ^ ) , neii biet kh6i luong cua (n - 1) chat thi tinh ducjc kh6'i luong cua chat con lai.
Phiromg phap hoa trj trung binh: Trong nhOng tru6ng hop h6n hop c6 hai gia trj hoa trj (hoac trang thai s6' oxi hoa) trd Idn ta c6 the' sir dung phuong phdp hod trj trung binh d^ giai quye't cac yeu c5u ciia bai toan.
Thi du: K h i h6n hap M g , A l tac dung vdfi axit H Q thi ta cQng c6 2 < hoa trj trung binh < 3.
2. Cac thi du minh hoa:
Thidu 1: Hoa tan hoan toan 1,805 gam h6n hop gdm Fe va kim loai X bang dung djch HCl, thu duoc 1,064 1ft khi H^. Mat khac, hoa tan hoan to^n 1,805 gam h6n hop tren bang dung djch HNO3 loang (du), thu duoc 0,896 lit khi NO (san ph^m khiJr duy nha't). Biet cac the' tich khi d^u do d diiu kien tieu chu^n. K i m loai X la
A . Z n B.Cr C. A l D. Mg
(Trich dethi tuyen sink Dai hoc nam 2013 - Khd'i A) Hu&ng ddn giai
S6 mol cac khi: nH2 = 0,0475 (mol); = 0,04 (mol) Ap dung c6ng thiic tinh nguyen tir kh6'i ta c6:
_ m^ J, _ 1.805-(0,04.3-0,0475.2).56 ^
"e(cho) 0-04-3 - (0,04.3 - 0,0475.2).3 "
N 1 2 3
M 9 18 27
Ket luan Loai Loai A l
Cap nghiem hop l i 1^ k = 3, M M = 27 (Al) p ^ p an diing la C.
% du 2: Hoa tan hoan toan 24 gam h6n hop X gdm M O , M(OH)2 va M C O 3 ( M f 14 kim loai c6 hoa trj kh6ng d6i) trong 100 gam dung djch H2SO4 39,2%, thu duoc 1,12 lit khi (dktc) va dung djch Y chi chira m6t cha't tan duy nha't c6 n6ng d6 39,41 %. K i m loai M la
A . Z n B. Ca C. M g D. Cu
^|^__ (Trich de thi tuyen sink Dai hoc nam 2013 - Khdi B) 305
Hu&ngddngidi 100 39 2
S6 mol axit sunfuric: nH2S04 = j ^ q ^ g = 0.4(niol) Khi sinh ra Ih. CO^: n r o , = = 0.05 (mol)
^"2 22,4
V i dung djch Y chi chira m6t chat tan => H2SO4 phan ling viira du, ch& tan
MSO4. ^ So d6 phan ung: X + H2SO4 (dung dich) Y (dung dich) + COzt
Theo dinh luat bao toan khd'i luong ta c6 (tinh khd'i luong dung dich sau phat, iing(m<H„„)):
mx + i " d d axil = m dd Mu + ^co2
mdd„„ = 24 + 100 - 0,05 . 44 = 121,8 (gam)
V i bao toan s6' mol ion 804" ntn: nj^^^ = 0 ^ 2 8 0 4 = 0,4(mol) 0 , 4 ( M + 96).100
Theo bai ra: — ^ ^ = 39,41 => M = 24 ( M la kim loai Mg) 121,8
Dap an dung la C.
S6 mol khi H,: = = 0,03(mol)
Thi du 3: Cho 1,67 gam h6n hop hai kim loai 6 hai chu ki lifin tifi'p thu6c nhom IIA (phan nhom chinh nhom II) tac dung hd't vdi dung djch H Q (du), thoat ra 0,672 lit khi H , (6 dktc). Hai kim loai do la
A. M g v a C a . B. Cava Sr. C. B e v a M g . D. SrvaBa.
(Trich De thi tuyen sinh DH - CD khoi B) Hu&ng ddn gidi
0,672 22,4
Dat c6ng thiic chung ciia hai kim loai lien tid'p nhom IIA la M . F I P U : M + 2HC1 > M C l j + H ^ t
0,03 (mol) 0,03 (mol)
w 1:67
0,03
Suy ra, hai kim loai ki^m th6 do la Ca (40 < 55,67) va Sr (88 > 55,67).
Dap an diing la B. . Thi du 4: Cho 3,024 gam m6t kim loai M tan he't trong dung dich HNO3 loang
thu duoc 940,8 ml khf N,Oy (san p h i n khir duy nha't, 0 dktc) c6 ti kh6'i doi vdi H , bang 22. Khi N,Oy va kim loai M la
A . N O v a M g . B . N ^ O v a A l . C. NjOvaFe. D. N O . v a A l . (Trich De thi tuyen sinh Dai hoc khoiAl Suyra: M j ^ = ^ = 55,67
Hu&ng ddn gidi Xac djnh khi N , 0 , : dN^Oy/H2 =
. ^ = 2 2
I (j.M • O t / M N. O y = 4 4 ( N 3 0 )
V a y k h i N , O y l a k h i N , 0 . 940 8
StfmolN^O: n^^o^ = ^ = 0,042 (mol) Taco: 2N^' +
0,336 <-
2.4e 2N*' 0,042. 2 (mol)
=>Ine,„hi„, =0,336 (mol) = T,n^^^^^^
Ap dung c6ng thiJc tinh nguyfin tiJr kh6'i ta c6:
M , = ^ . k = ^ . k = 9 k 0,336
"e(cho)
Do do, gia trj thoa man la k = 3 => M = 27 (Al) Dap an dung la B.
Thi du 5: Hoa tan hoan toan 2,9 gam h6n hop kim loai M va oxit cua no \ho nude, thu duoc 500 ml dung dich chiJa m6t chat tan c6 ndng d6 0,04M va 0,224 lit khf H , ( 0 dktc). Kim loai M la
A.Ba. B. K. C C a . D. Na.
(Trich De thi tuyen sinh Dai hoc khoi B) Hu&ng ddn gidi
Theo bai ra: n„ = = 0,01 (mol); n,^^ = 0,5. 0,04 = 0.02(mol).
22,4
Tru&ng hap 1: Kim loai M la kim loai k i l m => oxit li MjO. "
M + H , 0
M , 0 + H3O y
-ằ M O H + ^ H ^ t X 0,5 x (mol)
— > 2 M O H 2y (mol) Theo bai ra ta c6:
0,5.x =0,01 x + 2y = 0,02
M.x + (2M + 16).y = 2,9 Giai ra ta duoc: x = 0,02; y = 0 => loai.
Tru&ng hap 2: M la kim loai ki^m th6 => oxit la MO.
307
M + IH.O
X
M O + HjO y
M(OH)2 + H , t
X X
M(OH), y
Theo bai ra ta c6: -
x = 0 , 0 1 x + y = 0,02
M x + ( M + 16).y = 2,9 Vay kim loai M la Ba.
Ddp an dung la A.
x = 0 , 0 1 y - 0 , 0 1 M = 137 (Ba)
Thi du 6: X la kim loai thuoc phan nhom chfnh nhom I I (hay nhom I I A ) . Cho 1,7 gam h6n hcfp g6m kim loai X va Zn tac dung vdi luong du dung dich HCl, sinh ra 0,672 lit khi H . (d dktc). Mat khac, khi cho 1,9 gam X tac dung vai luong du dung djch H2SO4 loang, thi th^ ti'ch khi hidro sinh ra chua de'n 1,12 lit (a dktc). K i m loai X la
A. M g . B. Sr. C.Ba. D. Ca.
(Trich De thi tuyen sinh Cao dang khoi Aj Hu&ng ddn gidi
Sir dung phuong phap khoang gia tri de' giai bai tap nay. Theo cac dff kifen bai ta xac dinh duoc: 38 < Mx < 56,7. Trong cac kim loai hoa trj I I , chi c6 k i m loai Ca (M = 40) thoa man.
Dap an diing la D.
Thidu 7: Cho 7,1 gam h6n hop gom m6t kim loai kidm X va m6t kim loai ki^m th6 Y tac dung he't vdri luong du dung dich HCl loang, thu duoc 5,6 lit khi (dktc). K i m loai X, Y la
A. natri va magie B. kali va canxi C. liti va beri D. kali v^ bari (Trich dethi tuyen sinh Dai hoc khoi A) Hu&ng ddn gidi
Co nhieu each de gidi hdi nay, sau day ta si'rdung cdng thi'tc tinh nguyen tu^khd de gidi.
Theo bai ra: nH2 = 0 , 2 5 ( m o l ) => n, „ h o ) = 0,25.2 = 0,5 (mol) C6ng thiJc tinh nguydn tir kh6'i: M^^ =
+ N e ' u k = 1: M M = — . 1 = 14,2 0,5
+ Ne'uk = 2: M M = 14,2 . 2 = 28,4 14,2<Mx,Y < 28,4
m M e(cho)
-.k
308
vay M x = 23 (natri); My = 24 ( magie).
£)ap an dung la A .
Jhi du 8: Hok tan hoan toan 2,45 gam h6n hop g6m hai kim loai ki^m thd vao 200 m l dung djch HCl 1,25M, thu duoc dung dich Y chiia cac chat tan c6 n6ng d6 mol bang nhau. Hai kim loai trong X la
A. M g va Ca B. Be va Ca C. Be va M g D. M g va Sr.
(Trich dethi tuyen sinh Dai hoc khoi B) Hu&ng ddn gidi
Cin chu y voi bai nay cac chat tan trong dung djch Y, ngoai mu6'i clorua ciia hai kim loai kiem tho con c6 axit HCl con du.
TCr cac dO kien bai ra ta xac djnh duoc t6ng nguydn tir khd'i ciia hai k i m loai 2 45
kiem th6: M ^ L K T 1 + MKLK-P. = 25 Q 2 ) / 5 '^^
vay hai kim loai kiem tho la Be ( M = 9) va Ca ( M = 40). ulf.
Dap an diing la B.
3, Cac bai tap tir luyen: , Cau I : Nhiing mot thanh kim loai M (hoa trj II) c6 kh6'i luong 9,6g vao dung djch
chu-a 0,24 mol Fe(N03)3. Sau m6t thoi gian, dung djch thu duoc c6 kh6'i luong bang khoi luong dung djch ban dSu. Dong thcfi thanh k i m loai duoc la'y ra dem hoa tan hoan toan bang dung dich HCl du thi thu duoc 6,272 lit H , (dktc) K i m loai M la • • A N i B.Cd C . M g D . Z n
(Trich de thi thu Dai hoc khoi A, B nam 2013) Hu&ng ddn gidi
S6 mol electron kim loai M cho:
2
n e( c h o ) = "p^3+-l + nH2-2 =0,24.1 +6,272. = 0,8 (mol)
22,4
Ap dung c6ng thiJc xac djnh chat dua vao cong thiic tinh nguyen tiJr kh6'i ta c6:
M , . ^ . k = M 2 = 2 4 ( M g )
" e ( c h o ) "'^^
E>ap an dung la C.
2: Cho h6n hop Y gom Fe va kim loai M c6 hoa trj k duy nha't. Hoa tan hoan toan 3,61 gam h6n hop Y bang dung djch H Q thu duoc 2,128 lit H . , con khi hoa tan 3,61 gam h6n hop Y bang dung djch HNO3 loang, du thi thu duoc 1,792 lit khi N O duy nha't. Biet cac the ti'ch khi do 6 dktc va hidu sua't cac phan ihig la 100%. K i m loai M la
A - M g . B. Ca. C. A l . D . Z n . (Trich dethi thUDai hoc khoi A)
I m
Hudng ddn gidi
S6mo\c chart: =0,095(mol); 11^,0 =0,08(mol) S6 mol sit CO trong 3,61 gam h6n hop Y:
"Fe2+ " "NO-3 - -2 = 0,05 (mol) = n,^
Khdi lupng kim loai M c6 trong 3,61 gam h6n hop: ^ , mM = my - mp,= 3,61- 0,05. 56 = 0,81(gam) A p dung c6ng thiic tmh nguyfin tijf kh6i ta c6:
m M .k =
" e ( c h o )
Dap an diing la C.
m M n H 2- 2- n F e- 2
-.k = 0,81
0,095.2 - 0,05.2 = 9k:
C&u 3: Co 2 binh A, B dung tich nhir nhau diu d 0°C. Binh A chiJa 1 mol O., binh B chiia 1 mol Q j , trong m6i binh diu cMa 10,8 gam kim loai M hoa tri k duy nh&.
Nung nong cac bmh cho tdi phan ung hoan toan, sau do lam lanh binh tdi 0°C.
Ngircri ta nhan thaiy ti 16 ap suit trong hai binh bay gi5 la 7/4. Th^ tich cac chat ran khOng dang k^.
Kim loai M la
A.Zn. B.Mg. C.A1. D.Cu Hu&ng ddn gidi
Xac djnh sd' mol m6i khi phan thig vdi kim loai M:
1-x 7 Goi no2,p„, = x = > nc,2(pô) = 2x=> Y - ^ = - = > x = 0,3 Xac dinh nguydn tijf khSi cua kim loai M :
0,3.4 1 M = 2 7 : A1
M M -
" e ( c h o )
Dap an diing la C.
C^u 4: Cho 20 gam kim loai R (cr nhom A) tac dung vdi N , dun nong thu duoc chfl' ran X. Cho X vao nurdc du thu duoc 8,96 lit (dktc) h6n hop khi kh6 c6 ti khd'i so v6i vdi Hj bang 4,75. Kim loai R la
A.Na B.Ca C. Ba D. K Hudng ddn gidi
Theo bai ra, chat ran X tac dung vdi nirdc sinh ra h6n hop khi => trong X co con du kim loai R va R tac dung dugc vdi nude sinh ra H,.
So 66 cac phan ihig xay ra:
R ( O H ) ,
H2 (ymol)
I R •
rx + y = 0,4
^ 117x + 2y = 0,4.2,4,75
x=0,2
y = 0,2 =•
Sis dung c6ng thirc ti'nh nguyfin tix kh6'i ta c6:
mp . 20
M P = -.k = -.k = 20k k = 2
M R =40:Ca
"e(cho) "NH3-3 + nH2-2 pap an diing la B.
C&a 5' Hoa tan 1,44 gam m6t kim loai hoa tri I I trong 150 ml dung dich H 2 S O 4
0,5M. De' trung hoa axit du trong dung dich thu duoc, phai diing he't 30 ml dung djch NaOH IM. Kim loai do la
A.Ba B . C a C. Mg D. Be
Hu&ng ddn gidi
M + H2SO4 ) . M S 0 4+ H 2 t (1) ^ ;
H2S04 + 2NaOH >Na2S04 + 2H2O . ( 2 )
HNaOH =0,03.1=0,03(mol); nH2S04 =0,15.0,5 = 0,075(mol) nH2SO4(0=0'075-^^0,06(mol)
Theo (1) CO n ^ =nH2S04 =0,06(mol) 1,44
0,06 - = 24 • Mg Dap an diing la C.
Cftu 6: Hoa tan hoan toan 0,5 gam h6n hop g6m Fe va m6t kim loai hoa tri I I trong dung dich HCl thu duoc 1,121ft H, a dktc. Kim loai hoa tri n do la
A.Mg B.Ca C.Zn D. Be.
Hudng ddn gidi
Vi cac kim loai d6u hod tri I I n6n dat c6ng thiJc chung ciia Fe va kim loai cin tim la M.
PTHH: M + 2HC1 >MCl2 + t 1,12
M + 2HC1- 0,05 mol
22,4 = 0,05(mol) ".1 NguySn tijr khd'i trung binh ciia hai kim loai: M = = 10
0(05
Vi Mp, = 56 > 10 => Kim loai con lai c6 NTK < 10 kim loai hod tri I I la Be (M = 9 < 10)
Dap an diing la D. <
C a u 7: Cho 16,2 gam kim loai M c6 hoa tri n tac dung vdri 0,15 mol O2. Ch^t . „ . . „ - . ra^
thu duac sau phan umg dem hoa tan \ko dung dich H Q dir tMy thoat ra 13,44 1((
6 H 2 cJ dktc. K i m loai M la
A. Fe B. A l C. Ca D. M g
Hu&ng ddn gidi
Cach 1: Sir dung c6ng thiic tinh nguyfen tif kh6'i de' xac djnh k i m loai 16,2 . n = 9 n
cap nghiem thoa man la n = 3, M M = 27 ( M la k i m loai A l ) . Dap an dung la B.
Cach 2: Phuofng phap th6ng thudng
" 4 M + n02
— 4- 0 , 1 5 (mol)
M j O n +2nHCl 2MC1„ + n H j O
• M C L + - H , t M + nHCl
n -(mol)
" 2 13,44
22,4 = 0,6(mol) 0 , 6 ^ 1 , 2 1,8, ,x
— + — = —\mo\) n n n
16,2 S u y r a M , = ^ = 9„
+ n = 1 M = 9 (loai vi khfing c6 k i m loai nao) + n = 2^ M = 18(loai)
+ n = 3ii>M = 2 7( A l ) Dap an diing la B.
C a u 8: Cho 9,6 gam b6t kim loai M vao 500 ml dung dich HCl I M , khi phan tmg k^'t thijc thu duoc 5,376 lit H , (dktc). K i m loai M la
A . M g B. Ca C. Fe Hu&ng ddn gidi Cach 1: Sir dung c6ng thiic tinh nguyen tir kh6'i:
D.Ba.
M = 9,6
5,376 -.k = 20k:
22,4 Dap an dung la B.
.2
k = 2
M = 40 (Ca)
^jich 2: Dira vao cac dap an da cho thi cac k i m loai d^u c6 hoa trj I I
M + 2HC1 > MCI2 + H2 • ' ' ' HM = " H2 = ^ ^ = 0,24(mol)
V a y M M = - = - ^ = 40 ^ M l a C a n 0,24
Dap an dung la B.
C&o 9: Dien phan nong chay mu6'i clorua ciia kim loai M . d catot thu duoc 6 gam kim loai va a anot c6 3,36 lit khi (dktc) thoat ra. Mu6'i clorua do la
A . N a C l B. KCl C. BaCl, D. CaCl2 Hu&ng ddn gidi
2MC1„ > 2 M + n C l . -0,15 (mol)
'2 (I) 0,3
n
n c . 2 = | ^ = 0,15(mol) =^ n ^ = ^ = ^ ( m o l ) B . '
^•^y'* n n
Taco: ^ ^ ^ = . 6 = > M - 2 0 n n
Cap gia tri thoa man la n = 2 M = 40 (Ca)
Vay mu6'i clorua do la CaCl. ' ' Dap an diing la D.
Cau 10: Dien phan mu6'i clorua ciia m6t kim loai ki^m nong chay, thu diroc 0,896 lit khi (dktc) a anot va 3,12 gam kim loai 0 catot. Hay xac dinh c6ng thiic phan tir ciia mu6'i k i m loai kiem do.
Hu&ng ddn gidi 2MC1 ^ P 2 L - > 2 M + CI2
0,08 (mol) <r- ^ ^ = 0,04(mol) 22,4
M w = — 39 ^ M la kim loai K.
M 0,08 •
11: Cho 3,1 gam h6n hop g6m hai kim loai ki^m 6 hai chu ky ke' tidp nhau
^rong bang tuSn hoan tac dung het vdi nude thu dugc 1,12 li't H j or dktc va dung djchki^m.
djnh tdn hai kim loai do va tinh thanh phin phin tram khd'i luong mdi kim loai.
"^'nh th^ tich dung djch HCl 2 M cSn dung di trung hoa dung dich kiem va kh6'i
lirong h6n hop mu6'i clorua thu diroc. ,
Hu&ng ddn gidi a) Dat c6ng thirc chung cua 2 kim loai ki^m \k M .
M + HjO • M O H+ - H 2 t
! 0,1 < 0,1 < - ^ ^ = 0,05 (mol)
2 2 , 4
0,1
< Suyra2kimloaiki^mmNa(M = 2 3 < 3 1) v a K( M = 39>31) Goi X la s6' mol kim loai Na, ta c6:
23x + 39. (0,1 - x) = 3,1 =:> X = 0,05 (mol) Vay thanh ph5n % kh6'i luong m6i kim loai:
23.0,05.100%
%niNa= =37,1%
% m K =100-37,1 =62,9%
b) HCl + MOH > MCI + H2O
" H C i = n i ^ H = " M = 0 ' l ( ' " o ' )
Vay: The ti'ch dung dich HCl cin dung: V^JHCI " Y " ^'^^ ^''^^ " ^""'^
Kh6'i lupng h6n hop mu6'i clorua thu duoc:
mH,™5i = (31+35',5). 0,1 =6,65 (gam)"
Cau 12: Cho 2 gam m6t kim loai thu6c nhom IIA tac dung het vdi dung dich HQ tao ra 5,55 gam mud'i clorua. Kim loai do la kim loai nao sau day?
A. Be; B. Mg; C. Ca; D. Ba Hu&ng ddn gidi
Dat c6ng thu-c kim loai hoa tri I I la M.
M + 2HC1 > MCI2 + H2 t 5,55-2
"MCIZ = " 0 2 = - r ^ = 0,05{mol) z:>M = — = 40(Ca)
0,05 ^ ' Dap an dung la C.
cau 13: Khi la'y 14,25 gam mu6'i clorua ciia m6t kim loai chl c6 hod tri I I va m^t lugmg mu6'i nitrat ciia kim loai do c6 s6' mol bang so mol mu6'i clorua thi th^y khac nhau 7,95 gam.
Xac dinh ten kim loai.
1 1 A
Hu&ng ddn gidi Goi s5 mol ciia mu^i M Q j la X, ta c6:
(M + 124).x - ( M +7l).x = 7,95 ^ X =0,15(mol) Suyra: MMa2 = ^ J ^ = 95 : ^ M = 95-71 = 24
^ M la kim loai Mg.
Êiằ 14: D6't chay hd't 1,08 g kim loai hoa trj III trong khi thu diroc 5,34 g mu6'i clorua cua kim loai do. Xac djnh kim loai.
Hu&ng ddn gidi f:•<::• \.>:\,YS..-- •' Goi M la kim loai c5n tim.
• PTHH: 2 M + 3 0 , > 2Ma3 ( 1 ) ' ' ^ ^ ..
mol da phan umg la = ^ ' ^ ^ j ^ ' " ^ = 0,06 (mol) Y u^c
0 0 6 2 '
aplieo (1) s6' mol kim loai phan ung la: nw = ' ^ " = 0,04 (mol)
HEh<$i liromg mol cua kim loai la : MM = = 27 (g/mol) i
w 0 , 0 4
Kim loai la Al.
Ckn 15: Cho 3 g h6n hop g6m Na va kim loai kilm M tac dung vdi nude. Di. trung h6a dung djch thu duoc cin 800 ml dung dich HQ 0 , 2 5 M . Kim loai M la
A. Li B.Cs. C.K. D.Rb Hu&ng ddn gidi
''oi M la c6ng thiic chung ciia hai kim loai kilm, ta c6:
nHa = 0,8.0,25 = 0,2 (mol)
M + H 2 O M O H + I H J T ( 1 ) MOH + HQ - > M Q + H^O ( 2 )
Tir(l)va(2):n,H = n„a = 0,2(mol) M = — = 15
0,2
Nguyen tijr khdi trung binh la 15 thi phai c6 m6t kim loai c6 nguyen tii kh6"i < 15 m6t kim loai c6 nguydn tir khfTi > 15. Vay chi c6 Li ( M = 7 ) va Na ( M = 23) phu hop. vay kim loai ki^m M \l Li.
^ p a n d i i n g i a A.
16: Cho 17 g hdn hop X g6m hai kim loai kiem dutig ke' tie'p nhau trong nhom
^ tac dung vdri nu6c thu duoc 6,72 lit H , (dktc) va dung djch Y.
H6n hop X g6m
, ^ L i v a N a B.NavSK C. KvaRb D.RbvaCs