Kha hc LTH mn Ha hc Thy Ngc L thuyt v bi tp v silic v hp cht

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L THUYT V BI TP V SILIC V HP CHT TI LIU BI GING

I. Silic 1. Tnh cht vt l Silic c cc dng th hnh: Silic tinh th v silic v nh hnh. Silic tinh th c cu trc ging kim cng, mu xm, c nh kim, nng chy 14200C. Silic tinh th c tnh bn dn, nhit thng dn in thp nhng khi tng nhit th dn in tng ln. Silic v nh hnh l cht bt mu trng. 2. Tnh cht ha hc Cng ging nh cacbon, silic c cc s oxi ha -4,0,+2,+4; s oxi ha +2 t c trng i vi silic. Silic v nh hnh c kh nng phn ng cao hn silic tinh th. a. Tnh kh Tc dng vi phi kim: Silic tc dng vi flo nhit thng, cn khi un nng c th tc dng vi phi kim khc:

0 4

2 4Si + 2F Si F+

(silic tetraflorua). 0 4

0t

2 2Si + 2O SiO+

(silic ioxit).

Tc dng vi hp cht: Silic tc dng tng i mnh vi dung dch kim, gii phng hiro: 0 4

2 2 3 2Si + 2NaOH + H O Na SiO + 2H+

b. Tnh oxi ha nhit cao, silic tc dng vi cc kim loi nh Ca, Mg, Fe, to thnh hp cht silixua kim loi:

0 40t

2Si + 2Mg Mg Si

(magie silixua).

3. Trng thi t nhin Silic l nguyn t ph bin th 2 sau oxi, chim gn 29,5% khi lng v tri t. Trong t nhin ch gp silic di dng cc hp cht, ch yu l ct SiO2, cc khong vt silicat v aluminosilicat nh : cao lanh Al2O3.2SiO2.2H2O; xecpentin 3MgO.2SiO2.2H2O; fenspat Na2O.Al2O3.6SiO2, .... Silic cn c trong c th ng vt, thc vt vi lng nh v c vai tr ng k trong hat ng sng ca th gii hu sinh. 4. ng dng v iu ch Silic siu tinh khit l cht bn dn c dng trong k thut v tuyn v in t. Pin mt tri ch to t silic c kh nng chuyn nng lng nh sng mt tri thnh in nng, cung cp cho cc thit b trn tu v tr. Trong luyn kim, hp kim ferosilic c dng ch to thp chu nhit. Trong phng th nghim, silic c iu ch bng cch t chy mt hn hp gm bt magie v ct nghin mn:

0t

2SiO + 2Mg Si + 2MgO

Trong cng nghip, silic c sn xut bng cch dng than cc kh silic ioxit trong l in nhit cao:

0t

2SiO + 2C Si + 2CO

II. Hp cht ca silic 1. Silic ioxit Silic ioxit SiO2 l cht dng tinh th, nng chy 1713

0C khng tan trong nc. Trong t nhin, SiO2 tinh th ch yu dng khong vt thch anh. Thch anh ch yu tn ti dng tinh th ln, khng mu, trong sut. Ct l SiO2c cha nhiu tp cht. Silic ioxit l oxit axit, tan chm trong dung dch kim c nng, tan d trong kim nng chy hoc cacbonat kim loi kim nng chy, to thnh silicat:

0

0

t

2 2 3 2

t

2 2 3 2 3 2

SiO + 2NaOH Na SiO + H O

SiO + 2Na CO Na SiO + CO

Kha hc LTH mn Ha hc Thy Ngc L thuyt v bi tp v silic v hp cht

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Silic ioxit tan trong axit flohiric:

2 4 2SiO + 4HF SiF + 2H O

Da vo phn ng ny ngi ta dng dung dch HF khc ch v hnh trn thy tinh. 2. Axit silixic v mui silicat a. Axit silixic Axit silixic H2SiO3 l cht dng keo, khng tan trong nc, khi un nng d mt nc:

0t

2 3 2 2H SiO SiO + H O

Khi sy kh, Axit silixic mt mt phn nc, to thnh mt vt liu xp l silicagen. Silicagen c dng ht m v hp th nhiu cht. Axit silixic l axit rt yu, yu hn c axit cacbonic nn d b kh CO2 y ra khi dung dch mui ca n:

2 3 2 2 2 3 2 3Na SiO + CO + H O H SiO + Na CO

b. Mui silicat Axit silixic d tan trong dung dch kim, to thnh mui silicat. Ch c silicat kim loi kim tan c trong nc. Dung dch m c ca Na2SiO3 v K2SiO3 c gi l thy tinh lng. Vi hoc g tm thy tinh lng s kh b chy. Thy tinh lng cn c dng ch to keo dn thy tinh v s. trong dung dch, silicat kim loi kim b phn hy mnh to ra mi trng kim:

2 3 2 2 3Na SiO + 2H O 2NaOH + H SiO

III. Cng nghip silicat 1. Thy tinh a. Thnh phn ha hc v tnh cht ca thy tinh Thy tinh thng thng c dng lm ca knh, chai l,...l hn hp ca natri silicat, canxi silicat v silic ioxit, c thnh phn gn ng vit di dng cc oxit l Na2O.CaO.6SiO2. Thy tinh loi ny c sn xut bng cch nu chy mt hn hp gm ct trng, vi v soa 14000C:

0t

2 3 2 3 2 2 26SiO + CaCO + Na CO Na O.CaO.6SiO + 2CO

Thy tinh khng c cu trc tinh th m l cht v nh hnh, nn khng c nhit nng chy xc nh. Khi un nng n mm dn ri mi chy, do c th to ra nhng vt v dng c c hnh dng nh mun. b. Mt s loi thy tinh Ngoi loi thy tinh thng thng nu trn cn c mt s loi thy tinh khc vi thnh phn ha hc v cng dng khc nhau. - Khi nu thy tinh, nu thay Na2CO3 bng K2CO3 th c thy tinh kali c nhit ha mm v nhit nng chy cao hn. Thy tinh kali c dng lm dng c th nghim, lng knh, thu knh..... - Thy tinh cha nhiu ch oxit d nng chy v trong sut gi l thy tinh pha l - Thy tinh thch anh c sn xut bng cch nu chy silic ioxit tinh khit. Loi thy tinh ny c nhit ha mm cao, c h s n nhit rt nh nn khng b nt khi nng lnh t ngt. - Khi cho thm oxit ca mt s kim loi, thy tinh s c mu khc nhau, do to nn cc silicat c mu. Th d: crom III oxit Cr2O3 cho thy tinh mu lc, coban oxit CoO cho thy tinh mu xanh nc bin. 2. gm gm l vt liu c ch to ch yu t t st v cao lanh. Ty theo cng dng ngi ta phn bit gm xy dng, vt liu chu la, gm k thut, v gm dn dng. a. Gch v ngi Gch v ngi thuc loi gm xy dng. Phi liu sn xut chng gm t st loi thng v mt t ct c nho vi nc thnh khi do, sau to hnh sy kh v nung 900 10000C s c gch v ngi. Sau khi nung, chng thng c mu gy nn bi st oxit trong t st. b. Gch chu la Gch chu la thng c dng lt l cao, l luyn thp, l thy tinh...C 2 loi l: gch inat v gch samt. Phi liu ch to gch inat gm 93-96% SiO2, 4-7% CaO v t st; nhit nung khong 1300 14000C. Gch inat chu c nhit khong 1690 17200C. Phi liu ch to gch samt gm bt samt chn vi t st v nc. Sau khi ng khun v sy kh, vt liu c nung 1300 14000C. Bt samt l t st c nung nhit rt cao ri nghin nh. c. Snh, s v men

Kha hc LTH mn Ha hc Thy Ngc L thuyt v bi tp v silic v hp cht

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- t st sau khi un nng nhit 1200 13000C th bin thnh snh. Snh l vt liu cng, g ku, c mu nu hoc xm. c bng v lp bo v khng thm nc, ngi ta to mt lp men mng mt ngoi ca snh. - S l vt liu cng, xp c mu trng, g ku. Phi liu sn xut s gm cao lanh, fenspat, thch anh v mt s oxit kim loi. s c nung hai ln, ln u 10000C, sau trng men v trang tr ri nung ln 2 1400 15000C. S c nhiu loi: s dn dng, s k thut. S k thut c dng ch to cc vt liu cch in, t in, buzi nh la, cc dng c th nghim. - Men c thnh phn chnh ging s, nhng d nng chy hn. Men c ph ln b mt sn phm, sau nung nhit thch hp bin thnh mt lp thy tinh che kn b mt sn phm. Lng gm s Bt Trng, cc nh my s Hi Dng, ng Nai,.. l nhng c s sn xut gm s ni ting. 3. Xi mng a. Thnh phn ha hc v phong php sn xut - Xi mng thuc loi vt liu dnh, c dng trong xy dng. Quan trng v thng dng nht l xi mng Pooclng. l cht bt min, mu lc xm, thnh phn chnh gm canxi silicat v canxi aluminat: Ca3SiO5 hoc 3CaO.SiO2, Ca2SiO4 hoc 2CaO.SiO2, Ca3(AlO3)2 hoc 3CaO.Al2O3. - Xi mng Pooclng c sn xut bng cch nghin nh vi, trn vi t st c nhiu SiO2 v mt t qung st bng phng php kh hoc phng php t, ri nung hn hp trong l quay hoc l ng 1400 16000C. Sau khi nung, thu c mt hn hp mu xm gi l clanhke. ngui ri nghin clanhke vi mt s cht ph gia thnh bt mn, s c xi mng. b. Qu trnh ng cng xi mng Trong xy dng, xi mng c trn vi nc thnh khi nho, sau vi gi s bt u ng cng. Qu trnh ng cng ca xi mng ch yu da vo s kt hp ca cc hp cht c trong xi mng vi nc, to nn nhng tinh th hirat an xen vo vi nhau thnh khi cng v bn.

2 2 2 4 2 2

2 2 2 4 2

2 3 2 3 3 2 2

3CaO.SiO + 5H O Ca SiO .4H O + Ca(OH)

2CaO.SiO + 4H O Ca SiO .4H O

3CaO.Al O + 6H O Ca (AlO ) .6H O

Hin nay ngi ta cn sn xut cc loi xi mng c nhng tnh nng khc nhau: xi mng chu axit, xi mng chu nc bin... nc ta c nhiu nh my xi mng ln nh nh my xi mng Hi Phng, Hong Thch, Bm Sn, Chinfon, Hong Mai, H Tin...

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