32 305 2012 LkajyaHpc Xay diitig bai tap trac nghiem Hoa lioc thong qua cac tliih huong co van de trong day lipc IHoa hgc P G S T S C A O c y GIAC Khoa Hda hpc Trudng Dgi hpc Vinh V U MAI LIEN Cao hpe[.]
Trang 132 3 0 5 - 2 0 1 2 LkajyaHpc
Xay diitig bai tap trac nghiem Hoa lioc thong qua cac tliih huong co van de trong day lipc IHoa hgc
P G S T S C A O c y GIAC
Khoa Hda hpc Trudng Dgi hpc Vinh
V U M A I LIEN
Cao hpe 18 - P P D H Hda hpc - Trudng Dai hpc Vinh
I DAT VAN DE
Ngu xay dung duac he thdng bai tap trac nghiem khach
quan Iren co sd cae tinh hudng cd van de thi bai tap se dam
bao tinli khoa hpc v6 npi dung, logic ve cau tnic, phii hpp
vdi doi tupng hpc sinh, gdp phan nang cao hieu qua day
hoc ndi chung va day hpc Hda hoc ndi rieng theo hudng
hpc sinh nam vung kien thirc ca chicu rpng va chieu sau
Mat khac, hoc sinh phat tnen dupe ky nang giai bai tap va
phat trien tu- duy logic Qua dd gay himg Ihii cho mpi dpi
luong hpc sinh trong hpc tap
II NQI DUNG
1 Tinh hudng cd van de, van de va bai toan cd van de
- Tmh hudng co van de (THCVD) Id mgi kho khan dirge
chu the y thirc ro rang hay mo hd, ma mudn khac phuc tin
phai lim toi nhung tri ihi'rc mdi, ninnig phuong thi'rc hanh
ddng nidi
- Tinh hudng cd van de kich thich dupe tu duy hpc smh khi
hoc sinh s^n cd nliirng tn lliuc ban dau dap trng npi dung
cu the cua linh hudng, sin cd nhUng phuong tien tri dc de
"xir sir" vdi ndi dung cu the do, Trudng hop nay, THCVD
trd thanli vrfn de
Van de la tndt THCVD dugc chii the Hep nhan de giai
quyel dira tren cac plnrang lien sdn cd cua minh {in thuc,
ky ndng, kinh nghiem lim loi)
+ Mpi van de deu chiia dung THCVD, nhung khdng phai
bat ky THCVD nao cung deu la van de ca
I '"Van de chi xuat hien klii nao da hinh thanh cac dieu
kien de giai quyet chiing" (C Mac)
+ Chi dat ra van de khi nao kha nSng lim each giai quyet
van de dd da chin mudi d mdt hpc sinh, d mdt lop hpc
Vdn de lii mot cau hdi nay ra hay dugc dai ra cho chii
the md chii the chua biet ldi gidi tir Inr&c vd phdi tim ldi
sdng lao Idi gtdi nhung chii the dci cd san mdl s6 phuong
nC'n ban dau de su dung ihich hop vao viec tim ldi do
- Bid loan co vrm de la mdt van de giai quyet dupe vdi
nhQng dieu kien hay thdng sd chp irude
2 Ciic tinh hudng cd van de va bai tap ap dung
2.1 Tinh hudng "nghich ly - be tdc "
Tinh hudng cd vSn de dupe tao ra khi kien thirc hpc sinh da
cd khdng phu hpp vdi ddi hdi cua nhiem vu hpc tap hoac vdi thuc nghiem, vSn d^ dua ra moi nhin ih^y dudng nhir
vd li Irai ngirae vdi nguyen li da cdng nhan chung, theo nguyen tac nay se tao ra tinh hudng nghich H va be tac
* Tinli hudng nghich li : la vln dd mdi nhin dudng nhir vd
li trai xoay, ngirpc ddi klidng phii hcrp vdi nguyen li da dugc cdng nhan Diing trudc tin!) hudng nay hpc sinh tliudng ndi " V6 li klidng the tin dupe" Dieu nay thudng gap d cac nha klioa hpc ed nhirng phat minh ldi lac khi gap
su kien hien tuong klioa hpe trai vdi li thuyet duong ihdi dang thdng tri Chinh nhd nhiing phat mmh Idn dd ma cai nghich li da dupe giai quyet de dan den li ihuyet mdi phe
bd li thuydl cu ldi thdi " Thien tai la ban ciia nghich li" (Puskin)
* Tinh hudng be tac - La tinh hudng {li thuyel hoSc thirc nghiem) ma khi xem xet thi cd mau thuSn va neu dung li thuyet da biet de giai thich thi gap be tdc Khi dd phai van dung li Ihuyet hoac quy luat khac de giai thich
Vi du I : Tai sao N va P cd eiing dang cau hinh electron ngoai cung la n s ' n p ' rftiung N cd cdng hda tri la 3 con P ngoai cdng hda trj 3 cdn cd cdng hda trj 5?
A Do cau hinh electron ngoai ciing ciia P cd phan Idp d cdn N thi khdng
B Do kha nang hoal ddng hda hpc cda P manh han cua N
C Do d nliiet do thudng N tuong ddi tra ve mat hda hpc
D Do nhQng ly do khac
Hudng ddn Khi dpc de bai loan thi hpc sinh de din den
linh huong nghich ly, be tac Nhung sau khi lim hieu dirge epng hoa trj thudng lien quan den cau hinh electron thi van
de dupe giai quyet de dang
"I X I
Trang 2DgllMHpCsds 33
—> Chpn dap an A
Vi du 2: T^i sao nila la phi kim manh nhung khi N2 lai
tuong ddi tro d nhiet dp thudng? (hay tai sao nito la phi
kim manh lai tdn tai dupe trong tir nhien dudi dang tir do?)
A Nito ed ban kinh nguyen tir nhd
B Phan tir N2 khdng phan cue
C Nito cd dd am dien Idn nhat trong nhdm VA
D Lien ket trpng phan tir N2 la hen kSt ba ril bdn
Hudng ddn: Nilo la phi kim manh, nhung dan chat niia
hoat ddng hda hpe kem d nhiet dp thudng, ton lai dupe
irong tu nhidn (khi quyen) vi phan tu N2 ed lien ket ba
(N=N) rat ben, khdng the phan hity thanh nguyen tir khi
nhiel dp thap hpae khdng ed xiic tac —> Chpn dap an D
2.2 Tinh huong "lira chgn "
La linh hudng dai ra tnrde hpc sinh lira chpn ral khd khan,
vua eo le, vira oai oam ea ve lam li lan ky thuat giu'a hai
hay nhieu phuong an giai quyel ma hoc sinh chi duoc phep
chpn mdt ma thdi
Vi du 1: Hda tan 4,76g hdn hpp kim loai gdm Zn va Al cd
ti le moi 1 2 vao 400 ml dung djch HNO3 vua du thu duoc
dung djch X chira m gam mudi va khdng cd khi thoat ra
Gia trj m la '
A 25,8 B 26,4
C 27,8 D 24,6
Huang ddn • ui„ = 0,04 va UAI = 0,08 -^ ne(nhudng) =
2.nzn + 3,nAi = 0,32
Khdng cd khi thoat ra —> cd mudi NH4NO3 va ne{nhan lao
khi) = 0 Suy ra:
m = 4,76 + 62.0,32 + 80.0.04 - 27,8 - ^ Dap an C
Vi du 2: Phuong phap dieu chfi elanol nao sau day chi
diing trong phdng ihi nghiem?
A Len men glucozo
B TTiiiy phan dKn xuat elyl lialogenua Irong mdi Inrdng kidm
C, Cho etilen t^c dyng vdi HiSO^ loang ndng
D Cho hon hpp etylen va hai nudc qua thap chii-a HjP04
Hudng ddn T i t ca 4 trudng hop da cho deu cd ihe dieu
chd dupe etanol Tuy nhien Irong phdng Ihi nghiem, ngudi
la Ihuc hien nhanh biing phuang phap thiiy phan din xuat
ctyl lialogenua Irong mdi trudng kiem -^ Dap an B
2.3 Tinh hudng "igisao"
Lk tinh huong cd van de xuai hi^n khi yeu cau phai tim
kidm nguyen nhan ciia mdt kel qua ngudn gdc ciia mdt
hi^n tupng, tim Idi giai dap eho cau hdi " tai sao ?"
Day la tinh hudng phd bien thudng xuyen va rat hieu
nghigm irong qud trinh nh5n thirc chung va nhan thirc hda
lioc ndi rieng Trong day hda hpc, chiing ta thudng xuyen
g?p phai tinh hudng "lai sao" Dd la nh&ng khi cin giai
ihich hi^n lupng, nhi>ng tinh ch^l hda hpc d^a vao dac
diem thanh phan va cau tao cua cac nguyen td hay hpp chat hda hpc Loai tinh hudng nay giiip cho hoc sinh tich luy dupe vdn kien thuc vija ed chifiu rpng vira cd chieu sau
Vi du 1: Vi sao dung djch NH3 cd thd hda tan dupe Zn(0H)2?
A Zn(0H)2 la mot baza lan
B Zn{0H)2 la hidroxit luang tinh
C NH3 la mdt hop chSt ed cue va la mdt bazo y6u
D Zn"" cd kha nang tao thanh phuc chit tan vdi NH3
Hu&ng ddn: Khi cho Zn{0H)2 vao dung djch dung djch
NH3 thi ed phan ung sau:
Z n ( O H ) j + 4 N H 3 ^ [ C u { N H 3 ) 4 ] ( O H ) j ^ D a p a n D
Vi du 2: Tai sao H3PO4 khdng cd tinh oxi hda nhu HNO3?
A Do nguyen Hi P irong phan tir H3PO4 cd lai hda sp^
B Do nguyen tir P trong phan tu H3PO4 cd sd 0x1 hda la +5
C Do nguyen td P trong phan tir H3PO4 cd lai hda sp^ la dang lai hda b§ii va cd sd 0x1 hda la +5
D Do nhCrng ly do kliac
Huang ddn •
Nguyen tir N U-ong phan lur HNO3 cd cdng hda Iri IV, cd sd 0x1 hda -1-5 va lai hda sp^ Cdn trong phan lu H3PO4 nguyen tii P cd sd 0x1 hda la +5 va lai hda sp' la dang lai hda b^n nen khdng cd tinh oxi hda nhu H N O ,
H ,0 " ° \
Cdu lao ciia axil mine HNOi
Cdu lao cua axil pholphoric H_tP04
III KET LU.\N
Xay dung mdl he thdng bin lap tren co sd khai thac cac tinh hudng cd van de la vi^c lam can thiet ciia giao vien trong d^y hpc Mpi tinh hudng cd mpt ngudn gdc xuat phat khac nhau cd bieu hien ve tam ti khac nhau Do dd, cd nhQng each giai quyet khac nhau ma giao vien can phai nam v5ng de dan dat hpc sinh giai quyet van de mdt each Iron ven
T i l LIKU THAM KHAO:
1 Cao Cu Giac Bdi tap ly Ihuyet vd (hue nghiem Hda hoc,
lap I - Hda hoc Vd ca Nxb Giao due, H.2003
2 Cao Cy- Giac KT ihiidl phan lich vd giai nhanh bdi lap
trac nghiem hda hoc Nxb Dai hoc Qudc gia TP Hd Chi
Minh, 2009
3 Nguyen Ngoc Quang Li hidn dgy hoc Hda hoc Tap 1
Nxb Giao due, H.1994