Bai Tap Chuong Tinh the on Quoc Gia

8/21/2019 Bai Tap Chuong Tinh the on Quoc Gia

1/20

BÀI TẬP VỀ TINH THỂ ION - TINH THỂ PHÂN Tử http://www.chemistrystudy.com/

BÀI TẬP VỀ TINH THỂ ION - TINH THỂ PHN T!

DẠNG 1: Dựa vào cấu trúc mạng tinh thể để giải thích tính

chất của các phn t! "ài 1:T"i s#o $%&' phi(& )* iot d+ d*&' th%&' ho# m* ,h&' d& i0&1 Bi(t r2&'

$%&' phi(& thu3c m"&' ti&h th4 ph5& t61 "ài giải : 78u tr9c m"&' ph5& t6 $%&' phi(& )* iot ,m $;& )& ?* do c8u tr9c ti&h th4 cK# ,im cC&',h&' chR&' chFu tRt ?^m. im cC&' cL r8t &hi;u m*u s^c: ,h&' m*u_#&h dC&' _#&h ?D c5y c#m ` t# ha&' )*&' &5u )* cJ e&.

im cC&' sb chDy ,hoJ&' YY 7 &(u cL K _y.

http://www.chemistrystudy.com/http://vi.wikipedia.org/wiki/Thang_%C4%91%E1%BB%99_c%E1%BB%A9ng_Mohshttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%99_gi%C3%B2nhttp://vi.wikipedia.org/wiki/Xanh_lamhttp://vi.wikipedia.org/wiki/Xanh_l%C3%A1_c%C3%A2yhttp://vi.wikipedia.org/wiki/Da_camhttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%8Fhttp://vi.wikipedia.org/wiki/H%E1%BB%93ng_(m%C3%A0u)http://vi.wikipedia.org/wiki/V%C3%A0ng_(m%C3%A0u)http://vi.wikipedia.org/wiki/N%C3%A2uhttp://vi.wikipedia.org/wiki/%C4%90enhttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%99_Celsiushttp://vi.wikipedia.org/wiki/%C3%94xyhttp://vi.wikipedia.org/wiki/T%E1%BA%ADp_tin:Diamonds_glitter.pnghttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%99_gi%C3%B2nhttp://vi.wikipedia.org/wiki/Xanh_lamhttp://vi.wikipedia.org/wiki/Xanh_l%C3%A1_c%C3%A2yhttp://vi.wikipedia.org/wiki/Da_camhttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%8Fhttp://vi.wikipedia.org/wiki/H%E1%BB%93ng_(m%C3%A0u)http://vi.wikipedia.org/wiki/V%C3%A0ng_(m%C3%A0u)http://vi.wikipedia.org/wiki/N%C3%A2uhttp://vi.wikipedia.org/wiki/%C4%90enhttp://vi.wikipedia.org/wiki/%C4%90%E1%BB%99_Celsiushttp://vi.wikipedia.org/wiki/%C3%94xyhttp://www.chemistrystudy.com/http://vi.wikipedia.org/wiki/Thang_%C4%91%E1%BB%99_c%E1%BB%A9ng_Mohs


2/20


im cC&' cL ,hJ &%&' tD& s^c tRt do cL chi(t su8t $i(& i &h#&h )Si $ScsL&' D&h sD&'.im cC&' ,h&' d& i0&. im cC&' ?* m3t ch8t truy;& &hi0t tRt $i )McDc &'uyE& t6 Wc ?iE& ,(t chft chb )Si &h#u.

"ài $: Hy so sD&h sA ,hDc &h#u 'i


3/20


3ấu trúc tinh thể phn t! n45c đá"ài 6 : NSc D d+ t#& $%&' phi(& d+ $#y hCi iot d+ th%&' ho# nt"i s#o ti&h th4 ph5& t6 ?"i d+ &L&' chJy d+ $#y hCi &h )y1

"ải giải : N'#y &hi0t 3 th&' X ph>& ti&h th4 $%&' phi(& iot $F

phD hKy cDc ph5& t6 tDch ri r# ,h`i m"&' ti&h th4 )* ,huy(ch tD&

)*o ,h&' ,h ?*m t# d+ &h& r# mi cK# ch9&'.Tro&' ti&h th4 ph5& t6 cDc ph5& t6 )& ta& t"i &h &h


4/20


phC&' )Si cDc &'uyE& t6 &2m cDc U&h hM&h ?p phC&' &'uyE& t6 )* &'uyE& t6 ,hDc &2m t5m cK# cDc mft cK# hM&h?p phC&'. 78u tr9c &*y ch# l &'uyE& t6 tro&' m3t &'uyE& tR.Tro&' ti&h th4 hqc c8u tr9c ?p phC&' t5m mft Wc , hi0u ?*cc v#ce-ce&tered cu$ic.

$ G"&' t&h th4 ph5& t6 cK# &Sc D G"&' ti&h th4 &Sc D thu3c ?o"i ti&h th4 ph5& t6. GQi ph5& t6?iE& ,(t )Si $R& ph5& t6 ,hDc '>& &L &h8t &2m trE& $R& U&h cK#m3t hM&h t di0& ;u hM&h .Xl.

http://www.chemistrystudy.com/http://www.chemistrystudy.com/


5/20


78u tr9c cK# ti&h th4 ph5& t6 &Sc D thu3c c8u tr9c t di0& ?*c8u tr9c rQ&' &E& &Sc D cL tU ,hRi &h` hC& ,hi &Sc tr"&' thDi?`&' th4 tch &Sc D tr"&' thDi &' fc ?S& hC& ,hi tr"&'thDi ?`&'.



6/20


DẠNG #: 7ác đinh 0h8i /49ng ri(ng ;8 ph8i trí đ< đ=c 0hítcủa các cấu trúc mạng

"ài 1:

xDc F&h Ic cK# t\&' ?o"i c8u tr9c m"&'11. Khối lượng riêng của tinh thể: ρ &.G

N.Vt$&: zR C& )F c8u tr9c tro&' m3t t( $*o cC $J& sR {uJ c>u.G : ,hRi ?W&' ph5& t6 cK# C& )F c8u tr9c.Vt$: Th4 tch cK# t( $*o cC $J&.

N: sR |)'#r."ài #:

xDc F&h Ic P )* $D& ,&h cK# {uJ c>u ,im ?o"i tro&' m"&' ?p phC&'t5m ,hRi. Bi(t:

a

C

B

D

A

"ài giải:Theo m hM&h t# cL: }7 # k

|7 l~. )Si ~ ?* $D& ,&h cK# {uJ c>u.xt t#m 'iDc: |}7 ?* t#m 'iDc )u&' t"i }: |7k |} k • }7 k

l~k #k • k#k #k

~ # l

.

mQi {uJ c>u U&h L&' 'Lp X/ . V* t5m cL m3t {uJ & k h#y cL h#i {uJ c>u tro&' m3t c8u tr9c cC $J&.Vt$ #

Vc wl

w Rπ

@^p )*o c&' thc n P Y.Vy tro&' m"&' ?Si ?p phC&' t5m ,hRi: 3 fc ,ht €



7/20


€ ?Q trR&': k€.Ic .

"ài $:xDc F&h ~ P Ic cK# c8u tr9c ?p phC&' t5m di0& $i(t:

DC

B A

#"ài giải

Theo m hM&h n |} l~ m* t#m 'iDc )u&' t"i 7 n |} k |7 k • 7} k

~ # kl

zR C& )F c8u tr9c:• mQi {uJ c>u U&h L&' 'Lp X/• mQi {uJ c>u trE& mft L&' 'Lp & l.Ic Xk.th#y cDc 'iD trF )*o t# cL: P Y‚lVy tro&' m"&' ?p phC&' t5m di0&:- 3 fc ,ht ?* ‚l€- € cDc ?Q trR&' ?* k€.

"ài 2:TMm ~ Ic P cho c8u tr9c ?ƒc phC&' fc ,ht.

Bi(t:

VSi }H )u&' 'Lc )Si |B7

c

D

H

a

C

B

A

Bài giải

Theo m hM&h t# cL: |7 7B k~ t#m 'iDc |B7 c5& t"i 7



8/20


Gft ,hDc 'Lc |7B YY )M )y t#m 'iDc |B7 ;u |B # k~ h#y ~ #/kT# cL t di0& |B7} ?* t di0& ;u )M cDc c"&h ;u $2&' k~ VSi }H )u&' 'Lc )Si |B7 n }H c/k theo 'iJ thi(t.

H ?* trAc t5m cK# t#m 'iDc |B7 |H k # #

k T#m 'iDc |H} )u&' 'Lc t"i H. |} k |H k • H} k

#k ck/l • #k/

c k k

a

zR C& )F c8u tr9c:

• GQi {uJ c>u U&h L&' 'Lp X/.• mQi {uJ c>u mft L&' 'Lp X/k• mQi {uJ c>u tro&' L&' 'Lp X& • k • X .Vt$ c.zDyTh#y cDc 'iD trF )*o $i4u thc t&h t# Wc:3 dfc ,ht : ‚l€

€ ?Q trR&' : k€Ic Xk.

"ài 6:

T&h ,hRi ?W&' riE&' cK# ti&h th4 Ni $i(t Ni ,(t ti&h theo m"&' ti&h th4?p phC&' t5m mft )* $D& ,&h cK# Ni ?* Xkl Y A .

Giải:

#

#

# k l.r

# Yl l.XP kl

wP„Y‚h ik k

r A= = j P Y‚l

hRi ?W&' riE&' cK# Ni:

k

w.„P‚.YP‚l

l.wPXl.hXP kl.XY i .sPYk.XY−…Yl '/cm

"ài >: Za&' ,(t ti&h theo ,i4u ?p phC&' t5m di0&.

T&h ,hRi ?W&' riE&' cK# a&' theo '/ cm. 7ho 7u l.



9/20


Giải:

zR &'uyE& t6 7u tro&' m"&' ti&h th4:X X

. . l k

+ =

"ài ?. T\ &hi0t 3 ph[&' (& XX„ s^t ta& t"i d"&' veα )Si c8u tr9c ?p

phC&' t5m ,hRi t\ XX„ (& X‚ d"&' veγ )Si c8u tr9c ?p phC&'

t5m di0&. k… s^t cL ,hRi ?W&' riE&' d ‚‚l'/cm.

# T&h ,hRi ?W&' riE&' cK# s^t Xk„Y $` {u# J&h h&' ,h&' D&' ,4do sA d& & &hi0t.

Thp ?* hWp ,im cK# s^t )* c#c$o& tro&' L m3t sR ,hoJ&' trR&' 'i


10/20


c zR &'uyE& t6 tru&' $M&h cK# 7 tro&' mQi t( $*o sC &' cK# veα ?*:

€ . lPw.k.„„Pl‚YPlX

XkPYXX € .XkPYXX …„P‚.XkPYXX

C Fem C m

Fe= = =

d hRi ?W&' riE&' cK# m#rte&site: k hk.„„Pl‚ YP lX.XkP YXXi P kY /sPYkk.XY .hkP‚.XY i g g cm

cm−+

=

3u @ A 7ho r2&' h"t &h5& &'uyE& t6 )* ch&h &'uyE& t6 H cL d"&' hM&h c>u.H"t &h5& &'uyE& t6 hiro cL $D& ,&h '>& 9&' $2&' XY−X„ m $D& ,&h&'uyE& t6 hiro $2&' Y„ ×XY−XY m.

Hy _Dc F&h ,hRi ?W&' riE&' cK# h"t &h5& )* &'uyE& t6 hiro.cho ,hRi ?W&' proto& ,hRi ?W&' &Ctro& ≈ X‚k ×XY−k‚ ,' ,hRi ?W&' e?ectro& …XY… ×XY−X ,'

B45ng ,Cn♣ hRi ?W&' h"t &h5& &'uyE& t6 hiro ch&h ?* ,hRi ?W&' cK# proto& X‚k ×XY−k‚ ,'

• Th4 tch h"t &h5& &'uyE& t6 hiro $2&'

V 34 4

r3 3

× π = × Xl ×XY−X„ lX… ×XY−l„ m

hRi ?W&' riE&' cK# h"t &h5& &'uyE& t6 hiro $2&':

} 27

45

1,672 104,19 10

−

−

×

× …… ×XY t8&/m

• Th4 tch '>& 9&' cK# &'uyE& t6 hiro ?*:10 34 3,14 (0,53 10 )

3

−× × ×

Y ×XY−Y m

• hRi ?W&' cK# &'uyE& t6 hiro t&h cJ ,hRi ?W&' cK# e?ectro& X‚ ×XY−k‚ ,'

hRi ?W&' riE&' cK# &'uyE& t6 hiro $2&'27

30

1,673 100,63 10

−

−

×

× k ×XY ,'/m k ×XY '/cm

"ài : xDc F&h ,hRi ?W&' riE&' cK# N# G' .

Giải: xDc F&h ,hRi ?W&' riE&' cK# cDc ,im ?o"i trE& theo c&' thc:

} . .

l . A

M P

r π z#u L i;& )*o $J&' )* so sD&h ,hRi ?W&' riE&' cK# cDc ,im

?o"i L 'iJi thch ,(t {uJ t&h Wc.

im ?o"i N# G' |?



11/20


N'uyE& t6 ,hRi ).7 kk…… klX k…BD& ,&h &'uyE& t6 Y A X… X Xl

G"&' ti&h th4 @pt, @pc, @ptmZ3 fc ,ht Y Y‚l Y‚l

hRi ?W&' riE&' ? thuy(t '/cm Y…X… X‚lk k‚YhRi ?W&' riE&' thAc &'hi0m

'/cmY…‚ X‚l k‚

Nh& _t: hRi ?W&' riE&' t%&' theo th tA: } N# † }G' † }|?. @* do sA $i(& i c8u tr9c m"&' ti&h th4 ,im ?o"i 3 fc ,ht t%&' d>& )* ,hRi ?W&'mo? &'uyE& t6 t%&' d>&

Dạng $: 7ác đEnh Fán 0ính canh của hnh và 0hoảng cáchngHn nhất giIa hai tm của hai ngu'(n t! trong mạng tinh thể

"ài 1: Za&' ,(t ti&h theo ,i4u ?p phC&' t5m di0&.

T&h c"&h cK# hM&h ?p phC&' cK# m"&' ti&h th4 )* ,hoJ&' cDch &'^& &h8t

'i


12/20


T\ c&' thc: l.r # k → # l.r / k l.Xk.XY- /XlX .XY-

cm.

hoJ&' cDch &'^& &h8t 'i


13/20


7L: k.r N#• • r 7?- # „„.XY- cm → r N#• Y….XY- cmj

"ài $A T&h $D& ,&h &'uyE& t6 '>& 9&' cK# 7# kYY7 $i(t t"i &hi0t 3 L,hRi ?W&' riE&' cK# 7# $2&' X„„ '/cm. ˆiJ thi(t tro&' ti&h th4 cDc &'uyE&t6 7# cL hM&h c>u cL 3 fc ,ht ?* ‚l€.7ho &'uyE& t6 ,hRi cK# 7# lYYB45ng ,Cn

♣ Th4 tch cK# X mo? 7# 40,0!1,55 k„„ cm

m3t mo? 7# ch# N| Yk

×XYk &'uyE& t6 7#

Theo 3 fc ,ht th4 tch cK# X &'uyE& t6 ve 2325,!5! 0,746,02 10

×

× X

×XY−k cm

T\ V 34

r3× π

⇒ BD& ,&h &'uyE& t6 7# r 33V4π

23

33 3,1! 10

4 3,14

−× ×

× X…„ ×XY− cm

"ài 2A T&h $D& ,&h &'uyE& t6 '>& 9&' cK# ve kYY7 $i(t t"i &hi0t 3 L,hRi ?W&' riE&' cK# ve $2&' ‚‚ '/cm. ˆiJ thi(t tro&' ti&h th4 cDc &'uyE&t6 ve cL hM&h c>u cL 3 fc ,ht ?* €.7ho &'uyE& t6 ,hRi cK# „„„ lYB45ng ,Cn

♣ Th4 tch cK# X mo? ve

55,!5

7,!7 ‚Y…‚ cm

. m3t mo? ve ch# N| Yk×XYk &'uyE& t6 ve

Theo 3 fc ,ht th4 tch cK# X &'uyE& t6 ve 237,097 0,6!6,02 10

×

× Y ×XY−k

cm

T\ V 34

r3

× π

BD& ,&h &'uyE& t6 ve r 33V4π

23

33 0,! 10

4 3,14

−× ×

× Xkl ×XY− cm

"ài 6: Ph5& t6 7u7? ,(t ti&h dSi d"&' ?p phC&' t5m di0&. Hy $i4u di+&

m"&' cC s cK# 7u7?.

# T&h sR io& 7u• )* 7? - rai suy r# sR ph5& t6 7u7? ch# tro&' m"&' ti&h

th4 cC s.



14/20


$ xDc F&h $D& ,&h io& 7u•.

7ho: }7u7? lX '/cm j r 7?- XlY

| j 7u „ j 7? „„

Giải:

VM ?p phC&' mft t5m &E&

7?- U&h: Xc

Xc =× io& 7?-

mft: wk

Xs =× io& 7?-

7u• 'i: z^t d"&' α veα ,(t ti&h tro&' m"&' ?p phC&' t5m ,hRi &'uyE& t6cL $D& ,&h r Xkl #" Hy t&h:# 7"&h # cK# t( $*o sC &'

$ TU ,hRi cK# ve theo '/cm.c hoJ&' cDch &'^& &h8t 'i


15/20


X− = t5m ?p phC&' XVy t&' sR &'uyE& t6 7u ch# tro&' t( $*o sC J&' X • X k &'uyE& t6

$ T\ hM&h )b t# cL: |}k

#k

• #k

k#k

_t mft |B7}: |7k #k • |}k #k

mft ,hDc t# th8y |7 lr # 3 &E& # 4r3

4 1,24

3×

k„ #

c hoJ&' cDch &'^& &h8t 'i


16/20


= k„YY7 : NHl7? ,(t ti&h dSi d"&' ?5 Š p phC&' t5m diE Š&. $ T&h ,hoJ&' cDch:

kYY7: Y k Cl

ad A

− = =

"ài @: Hzˆ ˆ kYY zi?ic cL c8u tr9c ti&h th4 'iR&' ,im cC&'.

1. T&h $D& ,&h &'uyE& t6 si?ic. 7ho ,hRi ?W&' riE&' cK# si?ic ti&h th4

$2&' k'.cm-j ,hRi ?W&' mo? &'uyE& t6 cK# zi $2&' kX'.mo?-X.

#. zo sD&h $D& ,&h &'uyE& t6 cK# si?ic )Si c#c$o& r 7 YY‚‚ &m )* 'iJi

thch.

Giải:

#. T\ c&' thc t&h ,hRi ?W&' riE&'

} V A M n

.

. → VX .kX/k.Yk.XYk XYk‚ cm.

# „l.XY- cmj d w.a „l.XY- .X‚X ….….XY- cmj

BD& ,&h cK# &'uyE& t6 si?ic ?*: r d/ XX‚ .XY-cmj

$. 7L r zi YXX‚ &m n r 7 YY‚‚ &m. Zi;u &*y ph hWp )Si {uy ?ut $i(& i $D& ,&h &'uyE& t6 tro&' m3t ph5& &hLm ch&h

"ài . T\ &hi0t 3 ph[&' (& XX„ s^t ta& t"i d"&' veα )Si c8u tr9c ?p

phC&' t5m ,hRi t\ XX„ (& X‚ d"&' veγ )Si c8u tr9c ?p phC&'

t5m di0&. k… s^t cL ,hRi ?W&' riE&' d ‚‚l'/cm . Hy t&h $D& ,&h

cK# &'uyE& t6 ve.

G&J&: zR &'uyE& t6 ve tro&' m3t m"&' cC s ?p phC&' t5m ,hRi ?*: k

Y

k k

k.„„l‚ k.„„l‚k‚.XY k‚

Ykk.XY . Ykk.XY .‚‚l Fe

md a cm A

V a

−= = ⇒ = = =

Y l Xkl

l

aa r r A= ⇒ = =



17/20


DẠNG 2: K7L3 MNB %O PQ R+SGRDOS

K%TNB %BUNB )BVN )BVN %OWX %BY %T3B

ZB[NG G&RN %OQNG %OSNG XẠNG %&NB %BYA

"ài 1A BD& ,&h &'uyE& t6 7o$#?t ?* Xk„Ž. T&h th4 tch cK# C& )F cK#

ti&h th4 7o &(u tro&' X trt tA '>& _em 7o ,(t ti&h d"&' ?p phC&' t5mmft.



18/20


XPk„

XPk„

„

| B

7 }

| B

7 }

|} Xk„ . l „ Ž j |B „lPwk

„ k= Ž

Vy th4 tch cK# m"&' C& )F cK# 7o : V „l ll Ž

"ài #A G"&' ?Si ti&h th4 cK# 7? 'iR&' &h m"&' ?Si ti&h th4 cK# N#7?.= Xo7 ,hRi ?W&' riE&' cK# 7? $2&' X…… '/cm 3 d*i c"&h m"&'cC s _Dc F&h $2&' thAc &'hi0m ?* k…Yk Ž. }&' cDc 'iD trF cK#&'uyE& t6 ,hRi 4 _Dc F&h sR|)o'#dro. 7ho $i(t …Y…j 7? „l„B45ng ,Cn

xt m3t m"&' cC s Tro&' m3t m"&' cC s cL sR io& • hofc 7?- ?*: • l

Nh )y tro&' m3t m"&' cC s cL l ph5& t6 7?xt X mo? ti&h th4 7? ,hi L: hRi ?W&' 7? ?*: …Y… • „l„ ‚l„„X '

Th4 tch ti&h th4 7? ?*: ‚l„„X : X…… ‚l‚ cmTh4 tch m3t m"&' cC s ?*: k…Yk.XY- kl….XY-kk cm ⇒ zR m"&' cC s ?*: ‚l‚ : kl….XY-kk X„Y„.XYk

⇒ zR ph5& t6 7? cL tro&' X mo? ti&h th4 7? ?*: X„Y„.XYk _l

YkXk.XYk"ài $: Hzˆ ˆ kYY‚ ThAc &'hi0m cho $i(t ph# r^& )*&' |u cL ,hRi

?W&' riE&' ?* X…l '/cm )* cL m"&' ?Si ?p phC&' t5m di0&. Z3 d*i c"&h

cK# m"&' C& )F ?* lY‚Y.XY -XY m. hRi ?W&' mo? &'uyE& t6 cK# )*&' ?*:

X……‚ '/cm.

X. T&h ph>& tr%m th4 tch ,h&' 'i#& trR&' tro&' m"&' ?Si ti&h th4

cK# )*&'.

k. xDc F&h trF sR cK# sR |)o'#dro.



19/20


Giải:

#

#

# k l.r

- zR &'uyE& t6 tro&' X cC s:

.X/ • .X/k l.

- BD& ,&h &'uyE& t6 |u:

l.r # k → r # k /l Xl„.XY-

cm

Th4 tch $F chi(m $i cDc &'uyE& t6:

V&'uyE& t6 l/.π.r l.l/.Xl.Xl„.XY- „.XY-k cm.

Th4 tch X C& )F:VX # lY‚Y.XY- ‚lk.XY-k cm.

Ph>& tr%m th4 tch ,h&' 'i#& trR&':

VX - V&'uyE& t6.XYY / V&'uyE& t6 k€.

TrF sR cK# sR |)o'#dro: N| &.G/ }.V Yk.XYk.

"ài 2: Hzˆ ˆ kYY… GDu tro&' cC th4 &'i cL m*u ` )M ch#

hemo'?o$i& ch8t )& chuy4& o_i ch# s^t. GDu cK# m3t sR 3&' )t

&huy+& th4 ,h&' cL m*u ` m* cD m*u ,hDc )M ch# ,im ?o"i ,hDc x. T(

$*o C& )F m"&' cC s ?p phC&' t5m di0& cK# ti&h th4 x cL c"&h $2&'

k.XY- cm. hRi ?W&' riE&' cK# &'uyE& tR &*y ?* …kY ,'/m.

#. T&h th4 tch cK# cDc &'uyE& t6 tro&' m3t t( $*o )* ph>& tr%m th4 tch

cK# t( $*o $F chi(m $i cDc &'uyE& t6.

$. xDc F&h &'uyE& tR x.

Giải:zR &'uyE& t6 tro&' m3t t( $*o: .X/ • .X/k l.

T&h $D& ,&h &'uyE& t6: r Xk‚.XY- cm.

Th4 tch $F chi(m $i cDc &'uyE& t6 V &'uyE& t6 l.l/.π.r l.XY-k



20/20


cm.

Th4 tch X m"&' cC s V X # l‚.XY-k cm.

Ph>& tr%m th4 tch t( $*o $F chi(m $i cDc &'uyE& t6: ‚l€.

hRi ?W&' mo? ph5& t6: G X '/mo?. Vy x ?* a&'.

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