無機(jī)化學(xué)課件-5.酸堿反應(yīng)第五章

第五章酸堿反酸堿理論應(yīng)酸堿平衡酸堿平衡的計(jì)算緩沖溶液5.1

酸堿理論5.1.1

酸堿電離理論酸堿5.1.2酸堿質(zhì)子理論酸堿質(zhì)子理論1

酸堿定義凡是能提供質(zhì)子的物質(zhì)就是酸，凡是能接受質(zhì)子的物質(zhì)就是堿酸→質(zhì)子+堿HA

→

H+

+A-A-共軛酸堿對(duì)HClH2SO4Cl-HSO4--H2PO4-2--HPO42-+

H2PO4+

HPO4+

NH3NH4+H3PO4

-H2PO4

--NH3●●●2

酸堿反應(yīng)的實(shí)質(zhì)—質(zhì)子轉(zhuǎn)移反應(yīng)酸堿堿酸酸堿酸堿HOAc

→

H+

+

OAc-NH3

+

H2O

OH

-

+堿1

酸2

堿2酸1HA(酸)

H+H++ B(堿2)+ A-(堿1)HB

+(酸2)HA(酸1)+B(堿2)HB+(酸2)+A-(堿1)3

溶劑的酸堿性質(zhì)子溶劑特征質(zhì)子自遞反應(yīng)兩性溶劑酸性溶劑堿性溶劑惰性溶劑酸：能夠接受電子對(duì)的物質(zhì)堿：能夠給出電子對(duì)的物質(zhì)酸堿平衡溶劑的質(zhì)子自遞反應(yīng)氨化質(zhì)子甲醇化質(zhì)子醋酸化質(zhì)子質(zhì)子自遞反應(yīng)常數(shù)Kw?cB［B］w

3K

?

=

[H

O+

]

[OH-]Kw

=

[H3O+

]

[OH-]Kw

(

298.15K

)

=

1.0×10?

-14pKw

=

pH

+

pOH

=14KsKs

=[NH4+

][NH2-

]+

-Ks

=[CH3OH2

][CH3O

]Ks

=[H2OAc+

][H2OAc+

]5.2.2

弱酸和弱堿的解離反應(yīng)1

一元弱酸和弱堿Ka解離常數(shù)+

H2OHCOO-+

H3O+HCOOHKa=1.8×10-4HOAcKa=1.8×10-5+

H2OOAc-+

H3O+酸性減弱Kb解離常數(shù)減弱Kb堿接受HCl〉比它們強(qiáng)的都解離了Kw

=

[H3O+

]

[OH-]拉平效應(yīng)性溶劑拉平〉成為溶劑化質(zhì)子pKa

=

8.8pKa

=

9.4pKa

=

9.1區(qū)分效應(yīng)2.

多元弱酸和弱堿H3PO4

+H2OH3O+

+

H2PO

-4pKa2=7.20pKa3=12.36H2PO

-

+

H

O4

2H

O+

+

HPO

2-3

4HPO

2-

+

H

O4

2H3O+

+

PO

3-4pKa1=2.12

酸性減弱4PO

3-

+H2O

=

OH

-

+

HPO

2-44

2

2HPO

2-

+

H

O

=

OH

-

+

H

PO

-4pKb1pKb2pKb3=11.88=1.64

堿性=6.80

減弱H2PO

-

+

H

O

=

OH

-

+ H

PO4

2

34Ka1

Ka23.

共軛酸堿對(duì)的Ka和Kb之間的關(guān)系4.

解離度(α)和稀釋定律α100%

已解離的電解質(zhì)的濃度電解質(zhì)的總濃度

n已解離的電解質(zhì)100%n總初始濃度

c平衡濃度

c(

1

-

α)cα00cαKac

稀釋定律1/2α

=

(Kb

/c

)同離子效應(yīng)初始濃度0.100平衡濃度0.1－xxx初始濃度0.11.00平衡濃度0.1－x1.0+xx初始濃度0.11.00平衡濃度0.1－y1.0+2yy5.2.3

中和反應(yīng)強(qiáng)酸與強(qiáng)堿反應(yīng)：K

=1/

Kw強(qiáng)堿與弱酸反應(yīng)：b,A-w

Ka,HA1[A

]K

K[HA][OH

]

K強(qiáng)酸與弱堿反應(yīng)：Kw1[HA]K-b,AK

K

a,HA[H

][A

]弱酸與弱堿反應(yīng)：[HOAc][NH3

][H

]4[NH

][H

][OAc

][NH

][OAc

]K

4

[NH3

][HOAc]1[NH3

][H

][OH

][H

][OAc

]

[NH

][OH

]

4

[HOAc]

Ka,HA

Kb,(

NH3

)KwH3PO4

+

OH

-H2PO4-

+

OH

-HPO4

2-

+

OH

-H2O

+

H2PO4

-H2O

+

HPO42-H2O

+

PO4

3

-H+

+

CO3

2-H+

+

HCO3

-HCO3

-CO3

2-5.2.4

水解反應(yīng)及水解常數(shù)強(qiáng)酸弱堿鹽：強(qiáng)堿弱酸鹽：a,HOAc

Kb,OAc-[HOAc][OH

-

]KwKh

[OAc

]Ka,NH44b,NH3Kh

KKw

K[NH

][H

][NH

]3弱酸弱堿鹽水解：b,NH3KKwKa,NH

4a,HOAcKK

Kwb,OAcK

=

1/Kwa,HOAc

b,NH3K

KKwh總K

K

弱酸弱堿鹽的溶液的酸堿性：兩性物的水溶液的酸堿性：H2PO

-

+

H

O4

2H3O+

+HPO4a2pK

=7.202--H2PO4

+

H2OOH

-

+

H3PO4pKb3

=

11.883.酸堿平衡的計(jì)算1.

分布系數(shù)分布系數(shù)：δδ1δ0δ2δ1δ0a1

a1

a2K[H ]2

K

[H

]

K[H

]22

1Ka1[H

][H

]2

K

[H

]

K

Ka1

a1

a2

0Ka1

Ka2[H

]2

Ka1[H

]

Ka1Ka2

a1[H

]K[H

]Ka

23Ka1

a

2

a3[H

]

K

Kc[H

]3

K

[H

]2

K

Ka1

a1

a2[H

]3

[H3PO4

]

2c2

4a1[H

]3

K

[H

]2

K

Ka1

a1

a2[H

]

K

K

Ka1

a2

a3-[H

PO

]K

[H

]21ca1[H

]3

K

[H

]2

Ka1Ka2

[H

]

Ka1Ka2

Ka3[HPO2-

]K

K

[H

]

4a1

a20a1

a2

a33-[PO

]a1Ka

2

Ka3K

K

K4c

[H

]3

K

[H

]2

K

K

[H ]

Ka1

a1

a2Kb

[OH-]NH3[OH

]bK

[OH

]

bKb[OH

]

K4NH

14[H

]NHaK

[H

]

0NH3aK

[H

]Ka

2

分布曲線δcδ分布曲線分布圖δ0.8-0.6-0.4-0.2-034567pH=pKa=4.74δ1δ0●●●●●●●δ2a2[H

]

K[H

]

1a2Ka2[H

]

K

5.3.2

溶液平衡的基本關(guān)系式1.

物料平衡方程：（MBE）c

HOAccc

H3PO4c

Na2SO3書寫要點(diǎn)給定組分及各種可能形體2.

電荷平衡方程：（CBE）2[Na+]+[

H+]=[CN-]+[OH–]c

+[

H

+]=[CN-]+[OH–]3.

質(zhì)子平衡方程：（PBE）MBE：CBE：

23PBE：[H

]

2[H

PO

]

[H

PO

]

[OH

]

[PO3

]

[NH

]3

4

2

4

4

3得1個(gè)得2個(gè)

得1個(gè)

失1個(gè)

失1個(gè)

失1個(gè)得質(zhì)子后的產(chǎn)物H2PO4-失質(zhì)子后的產(chǎn)物H3O+

(H+)+H+H3PO4+2H+Na

++H+-H+-H+-H+OH

NH3PO43--[H+]+[H2CO3

]

=[OH-]+[CO3

]2-PBE4[H+]+2

[H3PO4]

+

[H2PO4

-

]

=[OH-]+[PO

3-

]+[NH3]5.3.3

酸堿水溶液pH

的計(jì)算●●●一般先用最簡式粗算，經(jīng)比較、判別后，再確定計(jì)算公式[H

]

K

[HA]

Ka

wc

Ka

≥10Kw[H

]

[H

]

cK

Ka

w近似式c

/

Ka

≥105c

Ka

≥10Kw最簡式(c

[H

])Ka近似式[H

]

cKac

/

Ka

≥105K

[A

]

Kb

w[OH

]

c

/

Kb

≥105[OH

]

c

Kb

≥10KwcK

Kb

w(c

[OH

])Kb[OH

]

c

/

Kb

≥105

c

Kb

≥10K[OH

]

cKbcKa1≥10Kw又：2Ka2/[H+]<<1又：c/Ka1>1052Kb2/[OH－]<<1c/Kb1>105cKb1≥10KwKa1>>

Ka2c

Ka2

>>

10Kwc

Ka2

>>

10Kwc

/Ka1≥10a1cKa1Ka2[H