, - ( - H3O+), - ( -). , , , , , , .
H3O+ pKa = 0, , pKa < 0. , , HClO4, HI, HBr, HCl, H2SO4, HNO3. . .
HClO4 + H2O H3O+ + ClO4-
, , OH- (pKBH+ = 14), . NH2-, O2-, CH3-, H- .
NH2- + H2O NH3 + OH-
, , , , , ( ), . pKa 0 - 4 ( !).
HSO4- + H2O SO42- + H3O+ (pKa =1,94)
pKa > 4:
H2S + H2O HS- + H3O+ (pKa = 6,99)
, pKBH+ 10 14, , , pKBH+ < 10, - .
S2- + H2O HS- + OH- (pKBH+ = 12,6)
C6H5NH2 + H2O C6H5NH3+ + OH- (pKBH+ = 4,6)
, , , , .
. (. 4.1).
. 4.1. pH 0,1
:
- ;
.
, , .. NH4+ , H3O+. , , , .
. , , .
, , (. 4.2).
. 4.2.
4.5.
() ( ) .
|
|
pH pH
pH pH
, , , , , paH pcH. , paH pcH, , .
0 14. , H3O+ , - .
:
HA + H2O H3O+ + A- H2O + H2O H3O+ + OH-
CHA > 10-6 /, H3O+, , .
CHA < 10-6 /, , .
, ,
, .
.
4.1. 0,01 HCl 0,01 NaOH, 1,0×10-8 HCl.
1) pH = -lg0,01 = 2,0 2) pH = 14,0 + lg0,01 = 12,0
3) pH = 6,98
, (, CO2) , HCl.
, ,
HA + H2O H3O+ + A-
( 5%), , [HA] CHA. , .
5%
:
pKa + lgCHA ³ 2,6
0,1 CH3COOH pKa + lgCHA = 4,75 1 = 3,75 (a < 5%), 0,1 H3PO4 pKa + lgCHA = 2,15 1 = 1,15 (a > 5%)
(HAKa < 10-12 pKa lgCHA < 12), , , .
,
B + H2O BH+ + OH-
, , . KBH+
BH+ + H2O B + H3O+
, [B] CB, [BH+] = [OH-] =
, [B] ¹ CB, [B] = CB [OH-]
4.2 0,10 CH3COOH (pKa = 4,76), 0,10 CCl3COOH (pKa = 0,70, Ka = 0,20), 0,10 NH4Cl (pKa(NH4+)= 9,24) 0,10 NH3 0,10 CH3COONa
1)
2) pKa + lgCHA = 0,7 1 = -0,7 ( 5%)
= 1,14
3) 4) = 11,1
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5) = 8,9
HA1 HA2, , , Ka1 Ka2.
5%, . , Ka[HA] >> KW, .
n
KaC , , , .
, , , HA1 , - .
,
, ( )
. , (, H2A HA-). Ka1 >> Ka2 [H2A] [HA-], , .
4.3. : 1) , 0,10 / CH3COOH (Ka = 1,75×10-5) 0,10 / HCOOH(Ka = 1,8×10-4);2) 0,10 (pKa1 = 4,04, pKa2 = 11,34); 3) 0,1 Na2CO3 ( pKa1 = 6,35, pKa2 = 10,32)
1) = 2,35
2)
3) = 11,7
HA- (, HCO3-) .
HA- + H2O H3O+ + A2- HA- + H3O+ H2A + H2O
, :
,
[HA-] CHA- [HA-] >> Ka1,
BH+A-
4.4. 0,10 NaHCO3 0,10 HCOONH4
1)
2)
4.6.
H2A.
= =
=
:
, :
, = pKa a(HA) = a(A-) = 0,5. Ka 1, - 10 , HA, 2 - 100 , 3 - 1000 .. a(HA) (. 4.3).
Ka 4 , , , . , H3PO4 (pKa1 = 2,15; pKa2 = 7,21) 3, , H3PO4 H2PO4-. , .
. 4.3. (pKa = 5)
4.5. [NH3] 0,10 / 7,0.
6,3×10-3