Ba2+, Sr2+, Ca2+, Pb2+.
: Ba2+ − [Xe]; Sr2+ − [Kr];
Ca2+ − [Ar].
( H2SO4)=2 /3 :
(BaSO4)=1,11010; (SrSO4)=3,2107;
(aSO4)=2,5105; (PbSO4)=1,6108.
( Pb(OH)2), . .
, aSO4. Ca2+ . Ca2+ . Ca2+ . Ca2+, .
BaSO4, SrSO4, aSO4 . 20 . , BaSO4, H2SO4.
. (NH4)2[a(SO4)2]. aSO4 . Ca2+ - 50-60% , aSO4. Ca2+.
Ba2+, Sr2+, Ca2+, Pb2+ :
(BaO3)=4,01010; (SrO3)=1,11010;
(aO3)=3,8109; (PbO3)=7,51015.
, , HCl, HNO3, CH3COOH.
aO3 :
aO3 + 2 + 2 → (3)2.
, .
4.3.1. Ba2+
Ba2+ .
Ba2+ :
1. - Ba2+ BaCrO4 :
Ba2+ + CrO42 → BaCrO4↓; (BaCrO4)=2,31010,
, (HCl, HNO3) , - -, BaCr2O7, SrCr2O7, CaCr2O7 .
2. 䳿 Ba2+ - :
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Cr2O72 + 2 2CrO42 +2+;
CrO42 + Ba2+ → BaCrO4↓.
Sr2+ Ca2+ =3-5. BaCrO4 . Pb2+ , - , .
Sr2+ Ca2+ SrCrO4, CaCrO4 䳿 , Cr2O72 , . Ba2+ Sr2+ Ca2+.
3. (NH4)2C2O4 Ba2+ BaC2O4, HCl, HNO3 3:
4. Na2HPO4 Ba2+ , HCl, HNO3 3: :
Ba2+ + HPO42 BaHPO4↓;
:
3Ba2+ + 2HPO42 + 2 Ba3(PO4)2↓ + 22.
5. ϳ . - .
4.3.2. Sr2+
Sr2+ .
1. Sr2+, , . , :
CaSO4 + Sr2+ → SrSO4↓ + Ca2+.
, Sr2+, . Ba2+, , - .
2. 䳿 Sr2+ - :
C2O42 + Sr2+ → SrC2O4↓,
, , .
3. - . , , .
Sr2+ .
4.3.3. 2+
a2+ .
1. a2+ :
CaCl2 + (NH4)2C2O4 → CaC2O4↓ + 2NH4Cl;
Ca2+ + C2O42 → CaC2O4↓.
, , , 1-2 . , , 3.
Ba2+ Sr2+ - , 2+ .
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:
(Ba2O4)=1,6107; (Sr2O4)=5,6108; (a2O4)=2,57109.
, , . , Ba2O4 , Sr2O4.
, H2SO4, , , .
2. a2+ .
, (( H2SO4)=2,0 /3). . , , .
. CaSO42H2O
(( H2SO4)=2,0 /3), , . BaSO4 SrSO4 SO4. - , .
3. K2CrO4 (CrO42) a2+ CCrO4:
a2+ + CrO42 → CCrO4.
, ( ) .
4. a2+ 䳿 () NH4+- :
a2+ + [Fe(CN)6]4 + 2NH4+ → a(NH4)2[Fe(CN)6]↓.
, a2+, 4[Fe(CN)6] NH4Cl, . - () .
. . , Ba2+ 䳿 4[Fe(CN)6] a(NH4)2[Fe(CN)6]. ( ) . .
5. a2+ . - .