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第八节 滴定曲线及指示剂的选择 PowerPoint PPT Presentation


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第八节 滴定曲线及指示剂的选择. 在酸碱滴定中 , 随着酸碱反应的 进行 , 溶液的 pH 值也随之变化。一 般来说 , 酸碱反应无外观变化 , 滴定 终点须借助酸碱指示剂颜色变化来 确定 , 为了选择合适的指示剂 , 必须 了解在滴定过程中溶液 pH 值的变化 规律 , 在计量点附近 pH 值的变化尤 其重要。. 滴定过程中溶液 pH 值的变化规 律 , 通常用滴定曲线来描绘。即 以 滴定过程中酸 ( 或碱 ) 标准溶液的加 入量为横坐标 , 溶液的 pH 值为纵坐

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第八节 滴定曲线及指示剂的选择

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6136181


6136181

,

, pH

, ,

, ,

pH

, pH


6136181

pH

,

()

, pH

, ,

, ,


6136181

1.

:

H+ + OH- H2O

0.1000mol/L NaOH

20.00mL 0.1000mol/L HCl,

pH


6136181

(1) ,

HCl

[H+]=c(HCl)=0.1000(mol/L)

pH= -lg [H+]=-lg0.1000=1.00

(2) ,

HCl


6136181

, 18.00mL NaOH

, HCl

2.00mL, [H+]


6136181

19.80mL NaOH,

HCl0.20mL


6136181

19.98mL NaOH,

HCl0.02mL

(-0.1%)pH:


6136181

(3) pH

20.00mL NaOH,

HCl,

[H+]


6136181

(4)

, 20.02mL NaOH

, NaOH0.02mL,

NaOH, :


6136181

pH,


0 1000mol l 1 naoh 20 00ml 0 1000mol l 1 hcl

0.1000molL-1 NaOH 20.00mL 0.1000molL-1 HCl


6136181

pH

sp+0.1%

*9.0

PP

8.0

*6.2

*4.4

MR

5.0

sp-0.1%

MO

4.0

3.1

T/%

0.10 molL-1

NaOH

0.10 molL-1

HCl

0.10 molL-1

HCl

0.10 molL-1

NaOH

PP 8.0

MR 5.0

PP 9.0

MR 6.2

MO 4.4


6136181

,

,

, ,

.

,

(0.1%)


6136181

0.1000mol/L HCl0.1000mol/L NaOH,

NaOHHCl,

pH.

pH9.70-4.30,

.

,(pH=4.0), (pH=3.1)

+0.2%


6136181

14

12

10.7

10

9.7

9.0

8.7

PP

8

pH

7.0

6

6.2

MR

5.3

4.3

5.0

4

4.4

MO

3.3

4.0

3.1

0.01molL-1

2

0.1molL-1

1molL-1

0

150

200

T/ %

0

50

100

NaOH

HCl

10, 2pH.


6136181

.,0.01mol/L, 0.10 mol/L,1.00mol/L

,pH

5.3-8.7,4.3-9.7,3.3-10.7.,

,,

; ,

,


6136181

,0.01mol/L NaOH

0.01 mol/L HCl,

,

,1%


6136181

2.

OH-+HAc Ac-+H2O

0.1000 mol/L NaOH

20.00mL 0.1000mol/ HAc

,


6136181

(1) pH

[H+]

HAc ,[H+]

,


6136181

(2)

HAcNaAc

,pH


6136181

c(HAc)= c(NaOH)=0.1000mol/L

,NaOH19.98mL

(-0.1%)


6136181

(3) pH

HAcNaAc,

Ac-Kbc(Ac-),

2-12 ,

,

c(Ac-)=0.1000/2=0.05000 (mol/L)


6136181

(4) pH

NaOHNaAc.NaOH,Ac-,pHNaOH.,0.1000mol/L NaOH20.02mL(+0.1%),

pOH=4.30 pH=9.70


6136181

,

pH,


0 10mol l 1 naoh 0 10mol l 1 hac ha 20 00ml k a hac 10 4 76 k a ha 10 7 00

0.10molL-1 NaOH0.10molL-1HAcHA(20.00mL , Ka(HAc) = 10-4.76, Ka(HA) = 10-7.00)


6136181

14

HAcAc-Ac-+OH-

12

10

9.7

9.0 PP

8.7

8

7.7

pH

6.2

4.43.1

6

MR

MO

HAc

4.3

4

2

HCl(0.10molL-1)

0

T/ %

0

50

100

150

200

0.10molL-1

NaOH

0.10molL-1

HAc

,.


6136181

pH

1molL-1

12

0.1molL-1

10.70

9.70

8.70

7.76

0.01molL-1

10

9.23

8.73

8.23

8

6

4.76

HAc

4

2

HCl

0 50 100 150T%

NaOH HAc ()

101pH


6136181

:

pH, HAc

, , [H+]

,NaOH

HAcHCl,

pH=1.00,

pH=2.88


6136181

pH

pH

, ,

,.

, Ac-

HAc, [H+]


6136181

NaOH,

NaAc,

HAc - Ac-,

pH,

, HAc,

, pH,

NaOHHCl


6136181

.,

,

0.1000mol/L

NaOH0.1000mol/LHAc pH

7.75-9.70.


6136181

Ac-, pH

7.00, 8.73.,

,

,

,


6136181

.0.1000mol/L

NaOH0.1000mol/L

,


6136181

I Ka=10-3, Ka=10-5,

Ka=10-7, Ka=10-9.


6136181

10

9.7

7.76

HA

pKa=7

HAc

4.3

pKa=4.76

HCl

0.10molL-1NaOH0.10molL-1 HA(Ka)

HCl:4.3-9.7

HAc:7.7-9.7

HA:9.7-10.0

Ka10, 1pH.


6136181

,(Ka), , , pH,.Ka 10-9,,, .H3BO310-9,pH, .


6136181

pH

.,

. ,

, pH0.3

pH,

<0.1%,cKa10-8


6136181

3.

0.1000mol/L HCl

20.00mL 0.1000mol/L NH3.H2O

pH

:

H++NH3H2ONH4++H2O


6136181

,pH

,

pH.


6136181

0.10molL-1

HCl

pH

12

NaOH

NH3

0.10molL-1

pKb= 4.75

10

9.0

NH3

8

8.0 PP

6.25

6.2

6

5.28

MR(5.0)

4.4

4.30

4

MO(4.0)

3.1

2

0 50 100 150 200 T/%

(NH3)

,


6136181

,

NaOHHAc,

pOH

, pH,

, NH4+

, H+,

pH7.00, 5.28


6136181

pH6.25~4.30,

,

, (Kb)

(c), cKb10-8,


6136181


6136181

  • (Ka10-6)Na2B4O7.10H2O() Na2CO3KCN


6136181

  • 2HCl + Na2B4O7 + 5H2O2NaCl + 4H3BO3

  • H3BO3(Ka17.310-10)(pH5.1)HClpH


6136181

(H2CO3)H2CO3(Ka14.510-7Ka24.710-11)HClNa2CO3

HCl + Na2CO3NaClNaHCO3

Na2CO3NaHCO3


6136181

  • (pH8.3)Ka1/ Ka2 104pH

  • (pH3.9)Ka1CO2CO2-


6136181

  • (C6H5NH2HCl)NH4Cl


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