, . - . , - . - . - .
, - , . , - - (); - - (). ( ), , - . , . , , . , , .
, 嗫b. , b 1 2, . , 2; .
1) , (CH3COOH) (NH3)
CH3COOH + H2O Û CH3COO- + H3O+
a1 b2 b1 a2
NH3 + H2O Û NH4+ + OH-
b1 a2 a1 b2
, . , , K Kb.
:
+ 2 H3O+ + B-
:
c(B-) c(H3O+)
Ka = ¾¾¾¾¾¾
c(HB)
. , . , , , .. Ka(CH3COOH) = 1,7410-5; Ka(C6H5OH) = 110-10.
:
+ 2 HB+ + OH-
Kb:
(OH-) (HB+)
Kb = ¾¾¾¾¾¾¾
(B)
:
Ka×Kb = Kw
, , , . , - 6H5O- , - CH3COO-.
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, , . . , : pKa = -lg Ka; b= -1g Kb.
pKb .
, pKa(CH3COOH) = - lg Ka(CH3COOH) = -lg1,7410-5 = 4,76.
Ka(C6H5OH) = 10.
, .
298 14:
pKa + pKb = 14
K .
.
(I) H3PO4 + H2O Û H3O+ + H2PO4-
a1 b2 a2 b1
c(H3O+)c(H2PO4-)
Ka(H3PO4)I = = 7,210-3
c(H3PO4)
(II) H2PO4- + H2O Û H3O+ + HPO42-
a1 b2 a2 b1
c(H3O+)c(HPO42-)
Ka(H3PO4)II = = 6,210-8
c(H2PO4-)
(III) HPO42- + H2O Û H3O+ + PO43-
a1 b2 a2 b1
c(H3O+)c(PO43-)
Ka(H3PO4)III = = 4,610-13
c(HPO42-)
, -, - -, .
Ka(H3PO4)II = Ka(H2PO4-); Ka(H3PO4)III = Ka(HPO42-);
(I-III) H3PO4 + 3H2O Û 3H3O+ + PO43-
, ( 2.14):
Ka(H3PO4) I-III = Ka(H3PO4)IKa(H3PO4)IIKa(H3PO4)III = 7,210-36,210-84,610-13 = 2,110-22.
, - (I) , (II) . - (II) - , (III) .
, , , .
. :
+NH3CH2COO- + OH- Û NH2CH2COO- + H2O
a1 b2 b1 a2
+NH3CH2COO- + H3O+ Û +NH3CH2COOH + H2O
b1 a2 a1 b2
. , : (CH3COOH NH3)
NH3 + CH3COOH Û NH4+ + CH3COO-
b1 a2 a1 b2
NH3 + H3O+ Û NH4+ + H2O
b1 a2 a1 b2
CH3COOH + OH- Û H2O + CH3COO-
a1 b2 a2 b1
(HCl NaOH)
H3O+ + - 2 + 2O
a1 b2 b1 a2
.
c(NH4+)c(CH3COO-)
K =
c(NH3)c(CH3COOH)
, :
c(NH4+)c(CH3COO-)(H3O+)
K =
c(NH3)c(CH3COOH)(H3O+)
:
c(NH4+) c(CH3COO-)(H3O+)
K =
c(NH3) (H3O+) c(CH3COOH)
, , :
Ka(CH3COOH) 1,7410-5
K = = = 3104
Ka(NH4+) 5,7510-10
, , , , , .
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. , , , , . , (, , , ) :
CH3COO- + H2O Û CH3COOH + OH-
b1 a2 a1 b2
Kh :
Kw
Kh(CH3COO-) =
Ka(CH3COOH)
, , , , . , , .
, , , . , (, , ) :
NH4+ + H2O Û H3O+ + NH3
a1 b2 a2 b1
Kw
Kh(NH4+) =
Kb(NH3)
, , , .
, , . -.
, - :
H2PO4- + H2O Û H3O+ + HPO42-; Ka(H2PO4-) = 6,210-8
, - :
H2PO4- + H2O Û H3PO4 + OH-; Kh(H2PO4-) = Kw:Ka(H3PO4) = 110-14: 7,210-3 = 1,410-12
(Ka > Kh) , , .. , .
, - .
: HPO42- + H2O Û H3O+ + PO43-; Ka(HPO42-) = 4,610-13
: HPO42- + H2O Û H2PO4- + OH-; Kh(HPO42-) = Kw:Ka(H2PO4-) = 110-14: 6,210-8 = 1,610-7
Kh > Ka, , , .
, . , .
, , :
CH3COOH + C6H5O- Û CH3COO- + C6H5OH
a1 b2 b1 a2
Ka(CH3COOH) 1,7410-5
K = = = 1,74105.
Ka(C6H5OH) 110-10
, . , , , ( ) ( ). , , .