Bo GD-DT tra loi thac mac ve de thi va dap an DH.

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Bo GD-DT tra loi thac mac ve de thi va dap an DH

Ket thuc ki thi tuyen sinh DH 2008, da co khong it thac mac cua thi sinh ve de thi va dap an. Sau khi duoc Dan tri chuyen tai nhung thong tin nay, Ban ra de thi cua Bo GD-DT da co van ban chinh thuc tra loi ve van de nay..

Bo GD-DT tra loi thac mac ve de thi va dap an DH - Ban co dau.
Bo GD-DT tra loi thac mac ve de thi va dap an DH - Ban khong dau.
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Bo GD-DT tra loi thac mac ve de thi va dap an DH.

Hang loat thac mac ve de thi, dap an cua doc gia Dan tri da duoc Ban ra de thi tuyen sinh quoc gia  giai dap mot cach chi tiet.

I. VAT LY:

Cau hoi 1: Tai ma de 128, cau 22 co hoi: Phat bieu nao sau day la sai khi noi ve anh sang don sac:

A. Anh sang don sac la anh sang khong bi tan sac khi di qua lang kinh.

B. Trong cung mot moi truong  truyen, van toc anh sang tim nho hon van toc anh sang do.

C. Trong chan khong, cac anh sang don sac khac nhau truyen di voi cung van toc.

D. Chiet suat cua moi truong  trong suot doi voi anh sang do lon hon chiet suat cua moi truong  do doi voi anh sang tim.

Theo dap an Bo GD-DT cong bo thi dap an dung phai la phuong an D.

Tuy nhien thi sinh  Thuy o Ha Noi  cho hay: “Trong luc lam bai thi em da thay co van de va sau ngay thi em da mang de di hoi mot so thay co day mon Ly cung duoc giai dap rang cau nay co 2 dap an, hay dung hon neu theo dap an cua Bo la dap an D thi o dap an B (trong de 128, cau 22) phai noi ro rang la “trong cung mot moi truong  truyen (khong ke van toc trong chan khong) van toc anh sang tim nho hon van toc anh sang do”.

* Tra loi cua Ban ra de thi:

Theo sach giao khoa Vat li 12 cai cach (tai lieu duoc dung chinh thuc de ra cau hoi  thi), khai niem “moi truong” khong bao gom “chan khong”. Dieu nay duoc the hien ro o cac dinh nghia ve chiet suat tuyet doi va ve y nghia vat li cua chiet suat tuyet doi nhu sau :

“Chiet suat tuyet doi cua mot moi truong  la chiet suat ti doi cua moi truong  do voi chan khong” (trang 124).

“ Chiet suat tuyet doi cua cac moi truong  trong suot ti le nghich voi van toc truyen cua anh sang trong cac moi truong  do”.

“Vi van toc anh sang trong cac moi truong  deu nho hon van toc anh sang trong chan khong, nen chiet suat tuyet doi cua cac moi truong  luon luon lon hon 1” (trang 125).

“Chiet suat tuyet doi cua moi truong  trong suot cho biet van toc truyen anh sang trong moi truong  do nho hon van toc truyen anh sang trong chan khong bao nhieu lan” (trang 125).

Cac dinh nghia va ket luan tren cung co tuong tu trong sach giao khoa 11 nang cao va co ban moi duoc bien soan lai.

Nhu vay, neu hieu khai niem “moi truong” bao gom ca “chan khong” nhu mot so nguoi quan niem thi khong phu hop voi sach giao khoa hien hanh va nhu the cung khong the xay dung  duoc khai niem chiet suat tuyet doi cung nhu khong xet duoc y nghia vat li cua no thong qua van toc truyen anh sang. Hai khai niem nay la khac nhau hoan toan.

Ket luan: Phuong an B (ma de 128) la dung hoan toan va khong can phai bo sung them dieu gi nua (va neu bo sung nhu trong y kien thac mac thi lai bi sai). Voi cau hoi  nay, chi duy nhat co phuong an D la sai hoan toan.

Cau hoi 2: Cau 5 (ma de 128): Cho khoi luong hat nhan  Be la 10,0135 u. Trong cac tai lieu  khoa hoc  va ca sach giao khoa vat ly 12 do la khoi luong cua nguyen tu Be. Ai cung biet rang de co khoi luong hat nhan phai lay khoi luong nguyen tu tru di tong khoi luong cac electron co trong nguyen tu.

Neu lay dung khoi luong hat nhan  thi dap an khong the nhu cua de thi da cong bo. Neu hoc sinh  nao lam dung nhu kien thuc  da duoc hoc (tru di khoi luong cua cac electron) thi ket qua khong nhu cua dap an da cho!

Cung trong cau nay, dap an cho don vi cua nang luong lien ket rieng la MeV. Viec lan lon don vi cua hai dai luong khac nhau nay la kho chap nhan cho mot ky thi quan trong  nhu the nay!

* Tra loi cua Ban ra de thi:

Khoi luong nguyen tu Beri la 10,0135u. Trong do tong khoi luong cac electron chi gan bang 0,002u, hoan toan co the bo qua so voi khoi luong hat nhan. Vi vay, do chi yeu cau hoc sinh  biet tinh nang luong lien ket rieng cua hat nhan  va yeu cau ve do kho trung binh cua cau hoi, cau hoi khong yeu cau phai lam phep tinh tru di cac khoi luong nay ma cho ngay khoi luong cua hat nhan  la 10,0135 u (luu y, de cho ngay khoi luong hat nhan chu khong cho khoi luong nguyen tu).

Neu thi sinh  lai co tinh hieu rang do la khoi luong nguyen tu thi da khong doc ky de bai va chi nho may moc mot cach giai da biet. Dieu nay cung tuong tu nhu trong mot so cau hoi, de don gian, nguoi ta cho gia toc roi tu do g=10 m/s2 nhung nguoi tra loi lai co tinh lay g=9,8 m/s2 la khong dung. Va nhu vay, dap an va cau tra loi deu phai lay khoi luong hat nhan  beri la 10,0135u la du kien moi dung.

Ve don vi nang luong lien ket rieng “MeV” la hoan toan chinh xac. Ta hay xuat phat tu dinh nghia dai luong nay : “Nang luong lien ket rieng la nang luong lien ket tinh cho mot nuclon” (sach giao khoa cai cach, phan ban). Tu dinh nghia nay ta thay nang luong lien ket rieng co cung thu nguyen voi nang luong. Do do don vi cua no phai la don vi nang luong, o day, trong vat li hat nhan, don vi thuong dung la MeV. Ve y nghia vat li, nang luong lien ket rieng la nang luong lien ket tinh trung binh cho mot hat nuclon trong hat nhan.

Vi vay, nguoi ta cung co the viet don vi cua no la MeV/nuclon. Chinh vi vay, voi sach giao khoa cai cach (dang dung pho bien hien nay) cac tac gia dung don vi MeV, voi sach giao khoa phan ban (thi diem), cac tac gia lai dung don vi MeV/nuclon. Tuy nhien, chung toi  nhan thay rang cach dung don vi MeV la don gian va phu hop hon ve mat thu nguyen vat li vi “nuclon” la mot hat, no khong phai la mot loai don vi vat li, vi vay bo no di la thich hop.

Dieu nay cung tuong tu nhu thay vi viet so Avogadro la 6,023.1023 nguyen tu/mol thi nguoi ta chi viet 6,023.1023 mol-1. Hay thay vi viet don vi cua tan so goc cua dao dong dieu hoa la rad/s thi chi viet don gian la s-1. Nhung dieu tuong tu nhu vay, hoc sinh  pho thong neu hieu ban chat van de deu phai thay duoc su tuong tu giua chung va co the chon don vi nang luong lien ket rieng la MeV hoac MeV/nuclon (hoac MeV/hat nuclon) ma khong the bi lam lan.

Hon nua, ngay trong bai tap 48.10 cua sach bai tap phan ban (thi diem), khi yeu cau tinh nang luong lien ket rieng cua cac hat nhan  cung cho dap so voi don vi la MeV (mac du ve li thuyet, sach nay cho don vi la MeV/nuclon).

Ket luan: Du kien cua cau trac nghiem  va dap an cua no la chinh xac, khong co su lam lan hoac sai sot gi.

Cau hoi 3: Cau 26 (ma de 128) dien dat khong chuan xac. Mot khung day co khong chi mot truc doi xung. Neu khung quay quanh truc doi xung vuong goc voi mat phang khung, ma duong cam ung tu lai vuong goc voi truc quay thi khung day khong cat duong cam ung tu nao ca! Vi de thi khac voi SGK la khong co hinh ve nen viec mo ta phai khong gay ra hieu nham. Neu tac gia  de thi noi ro truc quay la truc doi xung nam trong mat phang khung thi khong co gi phai ban ca.

* Tra loi cua Ban ra de thi:

Chinh nguoi hoi da tra loi mot phan cau nay. Chi co truong hop truc doi xung nam trong mat phang khung day va cac vecto cam ung tu vuong goc voi truc nay thi khi quay khung day quanh truc do tu thong qua khung day moi bien doi tuan hoan va do do moi co suat dien dong cam ung bien thien dieu hoa trong khung.

Neu truc doi xung vuong goc voi khung thi dieu nay khong the xay ra. O day, trong cac phuong an lua chon da khang dinh co suat dien dong cam ung.

Nhu vay, chi co the hieu duy nhat la truc quay phai nam trong mat phang khung day. Dieu nay cung tuong tu nhu trong cau hoi  tu luan co them du kien “biet trong khung co suat dien dong xoay chieu”. Day cung la mot su khac biet  giua cach ra cau hoi  theo hinh thuc trac nghiem  va tu luan. Chung toi  dong y de thi phai mo ta ro hon khi khong co dieu kien ve hinh nhung cung khong the mo ta thua va dai dong, lam thi sinh bi phan tan. Dong thoi, thi sinh  cung can phai co nhung suy luan them ve du kien khi doc cau hoi  de co cach lam dung va lua chon chinh xac phuong an tra loi.

Cau hoi 4: Cau 58 (ma de 128): Phan de dan cung can noi ro la cho thiet bi do tan so chuyen dong tren mot duong thang cho truoc di qua nguon am (coi la nguon diem). Vi neu khong, theo cach dien dat cua de thi, ta co the hieu thiet bi do tan so di chuyen theo phuong bat ky (khong di qua nguon am). Tat nhien o vi tri nao nguon am va thiet bi cung van cung nam tren duong thang.

Neu vay thi hien tuong xay ra khong don gian va ket qua thu duoc se khong giong nhu cac phuong an tra loi ma de thi da neu ra.

* Tra loi cua Ban ra de thi:

Phan dan cau trac nghiem  nay da cho du kien rat tuong minh: “Biet nguon am va thiet bi luon nam tren cung mot duong thang”. Du kien nay la day du de dien ta nguon am va thiet bi thu am  thoa man cac dieu kien de cho mot cach tinh va dap an duy nhat. Xin luu y den tu “luon” va “mot” cua de bai.

II. TIENG ANH

Cau hoi: Em la mot thi sinh  vua du thi dot II, ki thi tuyen sinh dai hoc  va cao dang  2008 - khoi D1. Sau khi xem xong dap an chinh thuc mon Tieng Anh  cua Bo Giao duc va Dao tao, em viet thu nay vi co thac mac o ma de 105 co cau so 80 (phan sua loi sai) nhu sau:

A child of noble birth, his name was famous among the children in that school.

            A                        B                             C                          D

Dap an cua Bo chon la B. His name.

 

Tuy nhien, theo chung em, cau hoi  cua de thi nhu vay chua hoan chinh ve ngu nghia cung nhu khong ro hien tuong ngu phap, vi vay khong the du thong tin  de xac dinh loi sai cho dung duoc. Neu dung la de thi co van de nhu vay, thi cac hoc sinh lam sai cau nay co quyen duoc tinh diem hay khong?

 

Em rat mong duoc Bo giai dap thac mac tren mot cach hop ly nhat, va dam bao duoc quyen loi cho thi sinh  chung em trong mot ky thi quan trong  nhu the nay.

 

* Tra loi cua Ban ra de thi:

Thac mac cua thi sinh  nao do ve cau trac nghiem  nay duoc giai thich nhu sau:

Day la loi thuoc ky nang viet do chu ngu cua hai ve khong dong nhat. Do vay, chi B la can phai sua, cac phuong an con lai (A, C va D) khong co loi.

Cau dung duoc viet nhu sau: "A child of noble birth, he was famous ...".  Cau tren la cau co dong va dac ngu cua cau dai hon "Being/As a child of noble birth, he was ..."

Ket luan: Cau trac nghiem  nay la chinh xac  va phu hop voi yeu cau cua de muc.

III. HOA HOC

Cau hoi 1: Khoi B: Cau 1 ma de 695 dap an cua bo la D tuc la co 4 chat tham gia phan ung trang guong nhung em chua hieu tai sao lai chi co 4 chat Vi C2H2, CH3CHO, HCOOH, HCHO deu tham gia phan ung trang guong dong thoi Mantozo cung tham gia phan ung trang guong.

* Tra loi cua Ban ra de thi:

Ve cau: Cho day cac chat: C2H2, HCHO, HCOOH, CH3CHO, (CH3)2CO, C12H22O11(mantozo). So chat trong day tham gia duoc phan ung trang guong la

A. 6.             B. 4.               C. 5.                  D. 3.

Phuong an B la dap an cua cau hoi  trac nghiem  nay.

Phan ung trang guong la phan ung dac trung cua nhung chat co nhom chuc andehit tac dung voi Ag2O (hoac AgNO3) trong dung dich NH3 sinh ra Ag bam vao thanh binh tao lop guong sang (trang 22, 26 SGK Hoa hoc 12 khong phan ban)

Trong so 6 chat neu tren, (CH3)2CO va C2H2 khong co chuc andehit nen khong co phan ung trang guong.

C2H2 tac dung duoc voi Ag2O (hoac AgNO3) trong dung dich NH3 nhung lai sinh ra C2Ag2 ket tua mau vang (trang 104, 105 SGK Hoa hoc 11 khong phan ban), nhu vay day khong phai la phan ung trang guong.

Cau hoi 2: Cau 18 ma de 195: Dun nong mot ruou (ancol) don chuc X voi dung dich H2SO4 dac trong dieu kien nhiet do thich hop sinh ra chat huu co Y, ti khoi hoi cua X so voi Y la 1,6428. Cong thuc phan tu cua Y la:

A. C3H8O. B. C2H6O. C. CH4O. D. C4H8O.

Theo phan anh thi phai tim cong thuc phan tu cua X moi dung. Vi neu la Y thi dap an cua Bo la sai.

* Tra loi cua Ban ra de thi:

 

Day la mot so suat dang tiec cua to bo mon trong khi bien tap cau trac nghiem  (dung ra la phai ghi X thi lai ghi la Y). Bo da co dieu chinh dap an va huong dan cham kip thoi truoc khi gui cac file cham cho cac don vi, theo do: khong cho diem doi voi cau nay, chia deu tong so diem cua toan bai thi cho cac cau con lai.

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Updated: 16/07/2008 | Views: 326 | Comments: 0

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Hien tai chua co binh luan nao ve bai viet Bo GD-DT tra loi thac mac ve de thi va dap an DH!

Ban co y kien gi ve bai viet Bo GD-DT tra loi thac mac ve de thi va dap an DH nay? Hay goi suy nghi, binh luan, danh gia, loi khuyen ... cua ban ve bai viet Bo GD-DT tra loi thac mac ve de thi va dap an DH ban tai day.

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