J. I. A L im j o n o V a, A. A. Is m a t o V
6-§. Gibbsning fazalar qonuni
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- Bu sahifa navigatsiya:
- P . = 1, F — 2 b o ‘ladi. ° n u n ’ m a x F = 0 , P
- F = 2; F = 0; P = 3. min ’ max 5 min ’
- 67-§. Bir komponentli sistemaning holat diagrammasi
- V2 s h a r t b a j a r i l g a n i d a m a n f i y b o ‘lishi m u m k i n : U n d a t g a , = d P / d T = Q / T
- V2> Қ va d P / d T
- V2> V l boMadi v a t e n g l a m a n i n g o ‘ng ta ra fid a g i d P / d T
- = d P / d T = Q / T { V V X) > 0 boMib, N N ’
- 68- §. S i 0 2 sistemasining polimorf modifikatsiyalari va undagi faza o ‘zgarish!ar
- 69-§. Kristall kremnezyom turlari
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6 6-§. Gibbsning fazalar qonuni G i b b s n i n g fa zalar q o n u n i q u y id a g ic h a t a ’riflanadi: h a r q a n d a y t e r m o d i n a m i k s is te m a d a erkinlik darajasi bilan fazalar s o n i n in g yig‘indisi k o m p o n e n t l a r s o n i n i n g ikkitaga k o 'p a y g a n ig a teng: F + p = к + 2, b u y e r d a : F — e r k i n l i k d a r a ja s i; P — f a z a l a r s o n i ; К — k o m p o n e n t l a r soni. A g a r s i s te m a b i r k o m p o n e n t l i boMsa, u n d a : / ■ ' + / * = 1 + 2 + 3. S i s t e m a n i n g m u v o z a n a t h o l a ti P . = 1, F — 2 b o ‘ladi. ° n u n ’ m a x F = 0 , P = 3 . m in ’ m a x B ir k o m p o n e n t l i s i s t e m a l a r d a n t a s h q a r i b a r c h a silik a tla r o ‘z g a r m a s b o s i m s h a r o i t i d a o ‘rg a n ila d i. S h u s a b a b d a n ikki va u n d a n o r t i q k o m p o n e n t l i s is t e m a l a r u c h u n G i b b s n i n g fa z a la r q o n u n i q u y i d a g i c h a yozilad i: F + P = К + I. U n d a ikki k o m p o n e n t l i s i s t e m a l a r u c h u n : F + P = 2 + 1 = 3 . P . = 1 ; F = 2; F = 0; P = 3. min ’ max 5 min ’ max X u d d i s h u k a b i u c h k o m p o n e n t l i s i s t e m a l a r u c h u n : F + P = 3 + 1 = 4 ; F = 3; P = 1; F = 0; P = 4 . max ’ min ’ min ’ max D e m a k , ikki k o m p o n e n t l i s is te m a l a r d a m u v o z a n a t n u q t a s id a 3 t a fa z a m a v j u d b o ‘lib, s i s te m a u n d a n c h e t g a c h i q q a n i d a 2 ta t e r m o d i n a m i k p a r a m e t r u n i n g h o l a t i n i a n iq la b b e r a o la d i. U la r g a t e m p e r a t u r a va k o m p o n e n t l a r d a n b i rin in g k o n s e n tra ts iy a s i kiradi. U c h k o m p o n e n t l i s is te m a la r d a e s a m u v o z a n a t h o l a t i d a 4 ta faza m a v j u d b o ‘lib, u n d a n c h e t g a c h i q q a n d a s i s t e m a n i n g h o l a t i n i 3 t a t e r m o d i n a m i k k o ‘r s a tk i c h a n i q l a y d i . U l a r g a t e m p e r a t u r a va u c h t a k o m p o n e n t n i n g ik k ita s ig a tegishli k o n s e n t r a t s i y a kiradi. Tayanch s o ‘z va iboralar Sistema, gomogen va geterogen, faza, fazalar muvozanati, komponent, bir kom ponentli sistem a, k o 'p kom pon entli sistem a, term odin am ik param etr, tem p eratu ra, bosim , konsentratsiya, hajm , m uvozanat holat, erkinlik darajasi, m uvo zan at nuq tasi, n o n v arian t n u q ta, qizdirish ch izig ‘i, sovitish chizig‘i, nam unalarni chiniqtirish , fazalar qonuni. ( | ) N a zo ra t savollari 1. Silikat sistem alar deb qanday sistem alarga aytiladi? 2. Sistem alar nim a m aqsadda o'rganiladi? 3. Sistemaning term odinam ik m uvozanat holati deb nim aga aytiladi? 4. H olat diagram m alarini qurishning necha xil usuli m avjud? 5. Sistem alarni o 'rg an ish d a holat diagram m alarining roli qanday? 6. H olat diagram m alarini o ‘rganishning aham iyati nim adan iborat? 7. G ibbsning fazalar qonu n in in g asl m ohiyati n im ad an iborat? 8. Sistem aning holatini qanday param etrlar aniqlab beradi? 9. Ikki k om pon entli sistem alar u ch u n G ibbsning fazalar qo n u n in i bayon eting. 10. U ch k o m ponentli sistem alar u ch u n G ibbsning fazalar q on un in i bayon eting. 67-§. Bir komponentli sistemaning holat diagrammasi B ir k o m p o n e n t l i s i s t e m a l a r u c h u n G i b b s n i n g f a z a la r q o n u n i g a k o ‘ra: P . = 1; F = 2 . n u n ’ m a x D e m a k , fa z a l a r so n i b i r g a t e n g boM gan s h a r o i t d a , s i s t e m a d a ikk ita t e r m o d i n a m i k k o ‘r s a t k i c h n i n g q i y m a t i n i o ‘z g a rtira o l a m i z . B u n d a s is te m a m u v o z a n a t d a n c h e t g a c h i q i b k e ta o l m a y d i . Bu t e r m o d i n a m i k p a r a m e t r l a r g a b o s im va t e m p e r a t u r a kiradi. B ir k o m p o n e n t l i s i s t e m a n i n g h o l a t d i a g r a m m a s i b o s i m b i l a n t e m p e r a t u r a bogM anishi a s o s id a t u z ila d i. Bu d i a g r a m m a d a ix tiy o riy b ir k o m p o n e n t n i n g 2 ta m o d ifik a ts iy a s i, y a ’ni p a st t e m p e r a t u r a l i va y u q o r i t e m p e r a t u r a l i (A t va A2) m o d ifik a ts iy a s i m a v j u d d i r . H o l a t d i a g r a m m a s i d a b ir fazali m a y d o n l a r 3 ta c h e g a r a d a n tashkil t o p a d i , u l a r n in g so n i 4 ga ten g . U l a r d a fa z a la r s o n i 1 g a , e r k in l i k d a r a ja s i esa 2 g a t e n g boMadi. B ir fazali m a y d o n d a n b o s h q a b ir fazali m a y d o n g a oMish c h e g a ra s id a fa z a la r so n i 2 ga, erkinlik darajasi e s a 1 ga teng. H o l a t d ia g r a m m a s id a b u oM ishlar M M va N/V c h i z iq l a r i b o ‘ylab r o ‘y b e r a d i. A g a r d a p a s t t e m p e r a t u r a l i m o d i f i k a t s iy a s i boM gan m a y d o n b ir fazali m a y d o n n i tash k il e tsa , u n d a u y e r d a fa q a t b i tta fa za, u h a m boMsa A x kristall faza m a v ju d d ir. S h u m a y d o n n i n g o ‘z i d a e r k in lik darajasi 2 ga teng. D e m a k , b iz s h u m a y d o n d a 2 ta t e r m o d i n a m i k p a r a m e t r n i , y a ’ni b o s i m v a t e m p e r a t u r a n i o ‘z g a rtirs a k h a m f a z a n i n g tu r i va h o l a t i o ‘z g a r m a y d i . H o l a t d i a g r a m m a s i d a b i r fazali m a y d o n l a r n i a j ra tib t u r g a n c h i z i q l a r b i r f a z a n i n g i k k i n c h i f a z a g a oM ishini b elg ilay d i. B u c h i z i q l a r b o ‘ylab Л, kristall m o d d a A2 kristallg a, A2 kristall faza s u y u q l i k k a h a m d a ikki xil k o ‘rin is h d a g i kristall va s u y u q f a z a la r b u g ‘ fa z a s ig a oMadi. D e m a k , b u c h i z i q l a r b o 'y l a b ik k ita faza m u v o z a n a t d a boMadi. S h u s a b a b d a n f a z a l a r s o n i 2 g a , e r k in lik d a r a ja s i e s a 1 ga t e n g boM adi. B u n d a f a q a t b i r t e r m o d i n a m i k p a r a m e t r n i o ‘z g a r t i r a o l a m i z , m u v o z a n a t e sa s a q l a n i b q o la d i; i k k i n c h i p a r a m e t r e s a b i r i n c h i s i g a bogMiq h o l d a o ‘z g a rib b o r a d i. H o la t d ia g ra m m a s id a 2 ta ev te k tik a n u qtasi m avjud. Bu n u q ta la r d a e r k in l i k d a r a ja s i 0 g a , f a z a l a r s o n i e sa 3 g a t e n g . B u n u q t a l a r d a 60-rasm . Ikkita polim orf ko'rinishiga ega boMgan en an tio trop o ‘zgarishli b ir kom ponentli sistem aning T— P diagram m asi. 3 t a fa za, y a ’n i M n u q t a s i d a ik k ita kristall va s u y u q fa z a la r , N n u q t a s i d a e s a kristall, s u y u q va b u g ‘ fa z a l a r m u v o z a n a t h o l a t i d a boMadi. B u n d a b i r o r - b i r t e r m o d i n a m i k p a r a m e t r n i o ‘z g a rtirs a k , s i s t e m a m u v o z a n a t d a n c h iq i b k e t a d i ( 6 0 - r a s m ) . F a z a l a r n i n g b i r - b i r i g a o ‘tish c h i z i q l a r in i n g t e m p e r a t u r a o ‘qi b i l a n oM m as yoki oMkir b u r c h a k hosil q ilis h in i K l a z i u s - K l a p e y - r o n t e n g l a m a s i a n i q l a b b e r a d i: d P /d T = Q / T ( V 2- Vt ), b u y e rd a : Q — y a s h i r i n s u y u q l a n i s h issiqligi; Vv V2 — p a s t v a y u q o r i t e m p e r a t u r a l i m o d i f i k a t s i y a l a r n i n g s o l i s h t i r m a h a j m i ; T — f a z a l a r n i n g m u v o z a n a t t e m p e r a t u r a s i . O M m as b u r c h a k n i n g ( a , ) t a n g e n s i m a n f i y i s h o r a g a e g a , b u Л Ш 1 chizigM v a t e m p e r a t u r a o ‘qi o r a s id a g i b u r c h a k n i n g t a n g e n - sidir: А' m o d i f i k a t s iy a t u r i n i n g A" ga oMish j a r a y o n i d a g i issiqlik effekti m u s b a t d i r , y a ’ni b u n d a issiqlik y u tila d i. B u s h a r o i t d a t e n g l a m a n i n g o ‘n g t o m o n i fa q a t V2 < Vl s h a r t b a j a r i l g a n i d a m a n f i y b o ‘lishi m u m k i n : U n d a t g a , = d P / d T = Q / T ( Қ - Қ ) < 0. D e m a k , t e m p e r a t u r a o s h i s h i b i l a n m u v o z a n a t l i b o s i m m i q d o r i k a m a y i b b o r s a ( M M " c h i z i q ) , y u q o r i t e m p e r a t u r a l i m o d ifik a tsiy a turi p a s t t e m p e r a t u r a l i m o d ifik a ts iy a tu rig a n i s b a ta n k ic h i k h a j m g a e g a boMadi. A m m o k o ‘p h o l l a r d a V2> Қ va d P / d T q iy m a t i m u s b a t d i r . O d a t d a s i l i k a t l a r s u y u q l a n i s h j a r a y o n i d a o ‘z h a j m l a r i n i o s h iris h la ri sa b a b li V2> V l boMadi v a t e n g l a m a n i n g o ‘ng ta ra fid a g i d P / d T q i y m a t n i n g m u s b a t boMishini t a l a b e t a d i va b u n d a /V7V chizigM v a t e m p e r a t u r a o ‘qi o ra sid a g i a 2 b u r c h a k o ‘t k i r boMadi: t g a = d P / d T = Q / T { V ~ V X) > 0 boMib, N N ’ c h izig M n in g g o r i z o n t a l o ‘q q a n i s b a t a n ogM shida k u z a t i l a y o t g a n i d e k , s u y u q l a n i s h t e m p e r a t u r a s i b o s i m n i n g o r t i shi b i l a n o s h ib b o r a d i. 68- §. S i 0 2 sistemasining polimorf modifikatsiyalari va undagi faza o ‘zgarish!ar K v a rs m o d i f i k a t s i y a l a r i n i n g b i r - b i r i g a o ‘t i s h i d a e n a n t i o t r o p h o d is a s i yu z b e r a d i, y a ’n i u l a r b i r - b i r i g a q a y t a r m a x a r a k t e r d a oMadi. K v a r s n i n g e n a n t i o t r o p p o l i m o r f o ‘z g a r is h la r i n i o d d i y b o s i m s h a r o i t i d a F e n n e r s x e m a si b o ‘y i c h a q u y id a g i t a r z d a aks e t t i r i s h m u m k i n : B u s x e m a b o ‘y i c h a k r e m n e z y o m n i n g asosiy m o d ifik a ts iy a la ri b o ‘lib k vars, t r i d i m i t va k ris to b a lit h is o b la n a d i. U l a r s x e m a d a g o r i z o n t a l c h i z i q b o ‘y i c h a jo y la s h tir ilg a n . B u 3 ta m o d if i k a ts iy a - n i n g h a r biri o ‘z h o l i c h a b i r n e c h t a m o d i f i k a ts iy a l a r g a ega, u lar a , p va у t a rz d a belgilanadi. E n g y u qori te m p e r a tu ra li m odifikatsiya a , e n g past te m p eratu ralis i esa у bilan belgilanadi. D e m a k , kvarsda 2 ta m odifikatsiya — a - va p - kvars, trid im itd a 3 ta modifikatsiya — a - , p - va y- trid im it, kristobalitda 2 ta m odifikatsiya — a - va p - k r i s t o b a l itl a r m a v j u d d i r . S x e m a d a g i k r e m n e z y o m s u y u q l a n m a s i va q u m t u p r o q s h ish a si a m o r f h o ld a g i k r e m n e z y o m g a ta a llu q li. K r e m n e z y o m n i n g a so siy m o d i f i k a t s iy a l a r g a o ‘tishi s e k in va b i r o z q iy in t a r z d a k e c h a d i , c h u n k i b u n d a kristall p a n j a r a n i n g tu z ilishida c h u q u r o ‘zgarishlar r o ‘y b eradi. B u n d a y oMishlarga a — kv arsn in g a - t r i d i m i t g a , a - t r i d i m i t n i n g a - k r i s to b a litg a o 't i s h i k ira d i. A k s i n c h a , b u m o d i f i k a t s iy a l a r n i n g h a r b ir i d a m a v j u d boMgan p a s t va y u q o ri t e m p e r a t u r a l i m o d ifik a ts iy a la rg a o ‘tish esa t e z v a o s o n k e c h a d i. C h u n k i u l a r n i n g kristall p a n ja r a s i b ir- b i r ig a a n c h a o 'x s h a s h . B u n d a y o ‘tis h la r g a m a s a l a n : p - k v a r s n in g a - k v a rsg a o ‘ti s h i, y- t r i d i m i t n i n g a - t r i d i m i t g a o ‘ti s h i, p - k r is t o b a - litn i n g a - k ris t o b a li tg a o 't i s h i kiradi. M o d i f i k a t s i o n o ‘z g a r i s h la r n i t e z l a tis h va u l a r n i o s o n l a s h - tirish m a q s a d i d a turli m i n e r a l i z a t o r l a r d a n fo y d a la n ila d i. K r e m n e z y o m n i n g b i r m o d i f i k a t s i y a d a n i k k i n c h is ig a oMish j a r a y o n i d a h a j m o ‘z g a r i s h l a r n i n g k u z a tilish i q a y d etilad i. B u kristall p a n j a r a n i n g o ‘z g a r i s h i d a n kelib c h i q a d i. Q u m t u p r o q n i n g b u s x e m a g a k i r m a g a n y a n a s u n ’iy ra v is h d a o l i n g a n va b a ’zi b i r h o l d a t a b i a t d a u c h r a y d i g a n q u y id a g i m o d i fik atsiy alari h a m m a v ju d : k itit, k o e s it, s tis h o v it, to lali k r e m n e z y o m va k r e m n e z y o m - 0. 69-§. Kristall kremnezyom turlari T a b i a t d a k r e m n e z y o m n i n g kristall tu rla ri j u d a k o ‘p ta rq a lg a n . U l a r n i n g q a r iy b b a r c h a s i d a S i 0 4 — t e t r a e d r l a r i u c h l a r i o rq a li b i r - b i r l a r i g a b irik a d i. L e k in tu rli m o d i f i k a t s i y a l a r d a t e t r a e d r l a r - n i n g b i r - b i r l a r i g a n i s b a t a n jo y l a s h is h i t u r l i c h a boMadi. S in c h t u z i l is h d a g i k r e m n e z y o m d a k is lo ro d b o ‘sh t a x l a n a d i. S h u s a b a b d a n u l a r n i n g s tr u k t u r a s i z i c h boM m aydi. S t r u k t u r a d a g i b u n d a y b o ‘s h l iq p a s t t e m p e r a t u r a l i m o d i f i k a t s iy a l a r d a k o ‘p r o q boMadi. S h u n i n g u c h u n e n g b o ‘sh s t r u k t u r a a - k r i s t o b a l i td a boMsa, e n g z i c h s t r u k t u r a p - k v a r s d a d ir. K v a r s . K vars s o ‘zi b i r i n c h i m a r o t a b a o ‘rta a s r la r d a S a k s o - n iy a d a p a y d o boMgan. U n i n g ikkita m odifikatsiyasi bor: p -k v a rs — t r i g o n a l s i n g o n iy a d a ; a - k v a r s — g e k s o g o n a l s i n g o n i y a d a b o ‘ladi. T a b i a t d a p - k v a r s k o ‘p r o q t a r q a l g a n , u y e r q o b ig M n in g a so s iy t a rk ib in i ta s h k il e ta d i. T a b i a t d a k v a r s n in g m o n o k r i s t a l la r i d e y a rli u c h r a m a y d i , le k in u la r k a t t a a h a m i y a t g a e g a m a t e r i a l - lard ir. S h u n i n g u c h u n u l a r s u n ’iy r a v is h d a o l i n a d i . T a b i iy kvars k r i s t a ll a r in i n g k o ‘pi g e k s o g o n a l p r i z m a h o l i d a u c h r a y d i. R auxtopaz. B u ra n g i q o ‘n g ‘i r d a n j i g a r r a n g g a c h a boMgan m i n e r a l . M orion — q o r a ra n g d a , sitro n — s a r iq o l t in r a n g d a boM adi, m o v iy k v a rs va p u s h t i k v a r s la r h a m m a v j u d d i r . A n a s h u k ris ta lla r 4 5 0 —6 0 0 ° C q i z d ir i l s a u l a r n i n g r a n g i k o 'k a r a d i . K i c h i k va m a y d a kvars k r i s t a ll a r in i n g a r a l a s h m a s i d a n t o m i r s i m o n kvars h o sil boMadi. U l a r d in a s , nafis k e r a m i k a m a h s u l o t l a r i o l i s h d a ishlatiladi. K v a rs b i r l a m c h i k o n l a r i n i n g s h a m o l t a ’s i r i d a o ‘z g a r i s h id a n q u m t u p r o q n i n g t o ‘p l a m l a r i , kvars q u m l a r i v u j u d g a k e lg a n , u la r k e y i n c h a l ik z ic h l a s h ib o d d i y q u m n i y o k i k v a rsitla rn i hosil qiigan. Q u m kvars d o n a l a r i d a n va u la rn i b i r - b i r l a r i g a b irik tir ib t u r u v c h i a m o r f h o l d a g i q u m t u p r o q m o d d a s i b i l a n h a m d a y a s h i r i s h k ris ta lla n g a n m o d d a b ila n hosil q ilin g a n b i r i k m a d a n ib o rat. U la r , a s o s a n , q u r i l i s h d a , d i n a s va fe rro s ilits id la rn i va kvars sh is h a s in i o l i s h d a i s h l a til a d i. T a b i a t d a y a n a b a ’z a n k v a r s n i n g m a y d a k u k u n s i m o n turi u c h r a y d i , u m a r s h a li t l a r y o k i o q kv ars un i d e b a ta lib , oMga c h i d a m l i m a t e r i a ll a r o l i s h d a is h la tila d i. K v a r s n i n g y a n a y a s h irin k r i s t a l l a n g a n tu r l a r i h a m m a v j u d . U la r g a x a l s e d o n , ag a t va y a s h m a l a r kiradi. X alsedon — b i r - b i r i g a y o p i s h g a n m a s s a d a n ib o r a t boMib, y a s h il, qizil, q o ‘ngMr, j i g a r r a n g h o l d a boMishi m u m k i n . U n i q i z d ir i b o ‘tga c h i d a m l i m a t e r i a l l a r o l i s h d a fo y d a la n i la d i. A gat — xalsedonning bir turi boMib, u turli rangdagi 10 m ik ro n - d a n i b o ra t y u p q a q a t l a m l a r d a n tu z ilg a n y a s h irin k ristallan g an , q a ttiq lig i 6 , 0 —6 ,5 , tu rli r a n g d a j i l o l a n a d i . U n d a n y o d g o rlik m a t e r ia ll a r i va te x n i k id ish la r yasaladi. M a s a la n , ag a t h o v o n c h a s i. Yashm a — x a l s e d o n n i n g b o s h q a t u r i boMib, u q izil, yash il, s a r iq , q o ‘ngMr, q o r a r a n g d a va u l a r n i n g q o ‘s h i lis h i d a n hosil b oM gan b o s h q a r a n g l a r d a u c h r a y d i . Q i m m a t b a h o y o d g o r l i k m a te ria li sifatida ishlatiladi. T r i d i m i t . 1868- yili R a t t o m o n i d a n k a s h f e tilg a n . T r i d i m i t n i n g 3 ta m o d ifik a ts iy a s i b or: y - t r i d i m i t , p - t r i d i m i t va a - t r i d i m i t . T a b i a t d a t r i d i m i t m e t e o r i t t a r k i b i d a , a s m a n i t m i n e r a l i sifa tid a , y a n a b a ’zi j i n s l a r t a r k i b i d a u c h r a y d i . U s u n ’iy ra v is h d a d i n a s g ‘ish tla rin i o l i s h d a ho sil b o 'l a d i . Kristobalit. 1884-yili M e k s ik a d a S e r r o - S a n - K r i s t o b a l v u lq o n i jin s la r i o r a s i d a n R a t i s h t i r o k i d a to p ilg a n . K r i s to b a l i t n in g 2 t a m o d i f i k a t s i y a s i b o r : a - k r i s t o b a l i t k u b i k s i n g o n i y a d a va p - k ris to b a lit t e t r a g o n a l s i n g o n i y a d a u c h r a y d i . T a b i a t d a a n d e z i t , d a t s i t , o b s i d i a n l a r ta r k i b i d a va v u l q o n tu fla ri t a r k i b i d a k e n g ta r q a lg a n . U h a m d in a sli g ‘isht o l i s h d a ho sil b o ‘ladi. Koesit — j u d a z i c h , m a y d a d o n l i s h a f f o f m a t e r ia l boMib, 1953- yili L . K o e s t o m o n i d a n s u n ’iy r a v is h d a o l i n g a n , m o n o k l i n s i n g o n i y a d a u c h r a y d i . T a b i a t d a k o e s i tl a r m e t e o r i t q u m l a r i t a r k i b id a top ilg a n . Melanoflogit — k u b i k s i n g o n i y a d a k r i s t a l l a n a d i . Q a t t i q l ig i 6 —7, u I t a l i y a d a to p ilg a n . U n i n g ta r k i b i d a S, С va H lar boMib, u l a r o r g a n i k q o ‘s h i m c h a l a r b i l a n tu rli r a n g la r ho sil q iladi. Stishovit 1961- yili S .M . S t i s h o v va S.V . P o p o v a l a r t o m o n i d a n s u n ’iy y o ‘l b ila n o l i n g a n . B u e n g z i c h ra n g siz s h a f f o f m in e r a l. S u n ’iy s tish o v it u z u n lig i 0 ,5 m m b o ‘lgan i g n a s i m o n k rista lla rd a n iborat. U m e t e o r q u m l a r i t a rk ib id a top ilg a n . B o s h q a m o d i f i k a t s i y a l a r d a n fa rqi H F k i s lo ta s id a e r im a y d i. Download 14.54 Kb. Do'stlaringiz bilan baham: 
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