31300531-kim-loại-kiềm-thổ-va-hợp-chất
TRANSCRIPT
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BI 26: KIM LOI KIM TH. MT S HP CHT QUAN TRNG CA KIM
LOI KIM TH
A. KIM LOI KIM TH
I.V tr v cu to
Kim loi kim th thuc nhm IIA, gm Be, Mg, Ca, Sr, Ba, Ra.
Cu hnh electron lp nggoi cng nS2
II.Tnh cht vt l
Nhit nng chy v nhit si tng i thp. cng cao hn kim loi kim
nhng vn thp.Khi lng ring tng i nh, l nhng kim loi nh hn nhm (trBa)
III.Tnh cht ho hc
Cc nguyn t kim loi kim c nng lng ion ha tng i nh, v vy kim loi kim
th c tnh kh mnh.
Tnh kh tng dn t Be n Ba: MM2+ +2e.
Trong cc hp cht , kim loi kim c th c s oxi ha l +2.
1.Tc dng vi phi kim:
V d: 2Mg + O2o
t
2MgO
2. Tc dng vi axit
a) Kim loi kim th kh c H+ trong cc dung dch axit HCl, H2SO4 thnh kh H2
M + 2H+M2+ + H2
b) Kim loi kim th kh c N+5 trong HNO3 long xung N-3; S+6 trong H2SO4 c
xung S-2.
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4Mg+10HNO3long4Mg(NO3)2+NH4NO3+ 3H2O
4Mg+50H2SO44MgSO4+H2S+ 4H2O
3. Tc dng vi H2O :
-Ca, Sr, Ba tc dng vi nc nhit thng thnh dung dch baz
V d : Ca +2 H2O Ca(OH)2 + H2
- Be khng tc dng vi nc.
- Mg tc dng chm vi nc nhit thng to ra Mg(OH)2,
Mg tc dng nhanh vi hi nc nhit cao to thnh MgO
2Mg +O2o
t cao
2MgO
B. MT S HP CHT QUAN TRNG CA KIM LOI KIM TH
1. Canxi hiroxit
- Ca(OH)2rn ,mu trng , t tan trong nc
- Dung dch canxi hiroxit l mt dung dch baz mnh :Ca(OH)2 Ca2+ +2OH- tc dng
vi oxit axit, axit ,mui.
Ca(OH)2+CO2 CaCO3 + H2O
Nhn bit CO2
- ng dng: ch to to va xy nh,kh chua, ty trng, kh trng, sn xut amoniac,
clorua vi, vt liu xy dng.
2. Canxi cacbonat
CaCO3 Cht rn mu trng, khng tan trong nc
-y l mui ca mt axit yu v khng bn,tc dng vi nhiu axit v c v hu c gii
phng kh CO2:
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CaCO3+ 2HCl CaCl2 +H2O +CO2
CaCO3 + 2CH3COOH Ca(CH3COO)2+H2O+ CO2
c bit:CaCO3 tan dn trong nc c cha kh CO2 :
CaCO3+ H2O +CO2 Ca(HCO3)2
Phn ng x y ra theo 2 chiu: chiu (1) gii thch s xm thc ca nc ma, chiu (2)
gii thch s to thnh thch nh trong hang ng.
3.Canxi sunphat
- CaSO4 cht rn mu trng, t tan trong nc.
C 3 loi:
+ CaSO4 . 2H2O :thch cao sng,bn nhit thng. CaSO4 . H2O :thch cao nung,
iu ch bng cch nung thch cao sng.
+ CaSO4: thch cao khan, iu ch bng cch nung thch cao sng nhit cao hn.
+thch cao nung thng dng c tng, phn vit bng,b bt khi gy xng
II. N C CNG
1. Khi nim
-Nc cng l nc c cha nhiu ion Ca2+, Mg2+
-Nc cha it hoc khng c cha ion Canxi ,magi gi l nc mm.
2. Phn loi nc cng
-Nc cng tm thi : nc c cha cc mi :Ca(HCO3)2 ,Mg(HCO3)2
-Nc cng vnh cu: nc c cha cc mui: CaCl2,MgCl2,CaSO4,MgSO4.
-Nc cng ton phn:nc c c tnh tm thi v tnh vnh cu.
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3. Tc hi ca nc cng:nc cng lm x phng t bt,nu thc phm b lu chin v
gim mi v,gy tc hi trong cc ngnh sn xut.
4. Cc bin php lm mm nc cng
-Nguyn tc: gim nng cation Ca2+,Mg2+ trong nc cng.
*Phng php kt ta:
-Vi nc cng tm thi: un si hoc dng Ca(OH)2 hoc Na2CO3 kt ta ion c
Ca2+,Mg2+, loi b kt ta ta c nc mm:
M(HCO3)2 MCO3+CO2 +H2O
-Vi nc cng vnh cu: Dung Na2CO3,Na3PO4,Ca(OH)2 d lm mm :
Ca2+ + CO32-CaCO3 3Ca2+ +2PO43- Ca3(PO4)2
Mg2+ + CO32-MgCO3 3Mg2+ +2PO43- Mg3(PO4)2
*Phng php trao i ion: Dng cht trao i ion(ht zeolit), hoc nha trao i ion.
Nc cng i qua cht trao
i ion l cc ht zeolit th ion canxi ,magi c trao i bng nhng ion khc nh H+,
Na+.ta c nc mm.