Chapter 7 Neutralization Titration (10-12)

EDTAAgNO3 nA n(A) mol, mmol, MA M(A) g . mol-1 cA c(A) mol . L-1mol/L

1> 99.9%2 3

21NaOH HClZn EDTA2Al3KMnO4 Ca

4K2Cr2O7 Na2S2O3

3

Theory of neutralization titrations (10)10A Solutions and indicators for acid/base titrations10A-1 Standard solutionsThe standard reagents used in acid/base titrations are always strong acids or strong bases, most commonly HCl, HClO4, H2SO4, NaOH, and KOH. Weak acids and bases are never used as standard reagents because they react incompletely with analytes.The standard solution employed in neutralization titrations are strong acids or strong bases because these substances react more completely with an analyte than do their weaker counterparts and thus yield sharper end points.

10A-2 Acid/base indicatorsAn acid/base indicator is a weak organic acid or a weak organic base whose undissociated form differs in color from its conjugate base or its conjugate acid form.

Methyl orange Phenolphthalein

Methyl orangeMO3.1-4.4pH4.4

Phenolphthalein PP

Phenolphthalein8.0-9.6, pH9.6

Indicator range

[In-]/[HIn][H+]Ka[In-]/[HIn]10, In-[In-]/[HIn]0.1HIn10>[In-]/[HIn] >0.1[In-]/[HIn]=1, [In-]/[HIn]10, [H+]Ka/10, pHpKa+1[In-]/[HIn] 0.1, [H+]10Ka, pHpka-1 indicator range =pKa1

pKapKa1

pKa3.43.1~4.45.24.4~6.29.18.0~9.6

pHpka-1pka+1pkapH0.2 pHMO 2.4-4.4 3.1-4.4PP 8.1-10.1 8.0-9.6

KaKaKac

c , a

mixed indicator 0.3 pH0.2 pH

pH 0 2 4 6 8

10B Titration curves1. changes in color due to the reagent, the analyte or indicator2. a changes in potential of an electrode that responds to the concentration of the reagent or the analyte

10B-1 Types of titration curves

10B-2 Concentration changes during titrations

10C Titration curves for strong acids and strong basesHClHNO3HClO4NaOHKOH,pHH+OH-pHTwo source:1. The reaction of the acid with water[H+] =[OH-]+Ca2. The dissociation of water[H+]=[OH-]-Cb

a molL-1 , b molL-1 0.1000 molL-1 NaOH 20.00 mL 0.1000 molL-1 HCl10C-1 The titration of a strong acid with a strong base

PBE[H+][H+] = [OH-] + a[H+] = a[H+] = [OH-] + a[H+] = a[H+] = [OH-]pH = 7.00[OH-] = [H+] + b [OH-] = b

C (mol.L-1) 1.00.100.0100.0010

V(NaOH)%pH0.000.001.0018.0090.002.3019.8099.003.3019.9899.904.3020.00100.07.0020.02100.19.70

C (mol.L-1)1.0003.30 ~10.700.10004.30 ~ 9.700.010005.30 ~ 8.70

1

30.00121

3.50.52.51.5

4132

4.51.53.52.5

5243

5.52.54.53.5

6354

6.53.55.54.5

7465

7.54.56.55.5

8576

8.55.57.56.5

9687

9.56.58.57.5

10798

10.57.59.58.5

118109

8.510.59.5

91110

9.511.510.5

101211

10.511.5

1112

11.512.5

1213

12.5

13

13.5

14

%

pH

Sheet1

0.0010.997700063801.0977000638-22.4425015956-81.78008669291.99770006380.05749840440.11512920381.0077000638-24.6925015956-98.01528245180.9987000638-24.9175015956-99.7997396744

0.10.50.31622776600.416227766-5.4056941504-51.94938532961.31622776617.094305849651.94938532960.326227766-7.6556941504-93.86931399370.317227766-7.8806941504-99.3695381633

0.11.00.100.200.00000000011.122.581.81818181820.11-2.25-81.81818181820.101-2.475-98.0198019802

251.50.031622776600.13162277661.70943058551.949385331.031622776624.20943058593.86931399370.0416227766-0.540569415-51.94938532920.0326227766-0.765569415-93.8693139936

12.00.0100.112.2581.81818181981.0124.7598.01980198040.0200.0000000050.011-0.225-81.8181818165

12.50.003162277700.10316227772.420943058693.86931399961.003162277724.920943058699.3695381640.01316227770.170943058651.94938536610.0041622777-0.0540569414-51.9493852931

3.00.00100.1012.475000000298.01980199981.00124.975000000299.80019980220.0110.225000000281.81818198350.0020.00000000020.0000005

3.50.000316227800.10031622772.492094306699.36953822621.000316227724.992094306699.93677444680.01031622770.242094306693.86931458790.00131622770.017094306651.9493889802

4.00.00010.00000000010.10009999992.497500002599.80019999981.000099999924.997500002599.98000201980.01009999990.247500002598.01980394080.00109999990.022500002581.8181983471

4.50.00003162280.00000000030.10003162252.499209438599.93677507251.000031622524.999209438599.99367570790.01003162250.249209438599.36954444810.00103162250.024209438593.8693734213

5.00.000010.0000000010.1000099992.49975002599.98000399941.00000999924.99975002599.998000220.0100099990.24975002599.80021976030.0010099990.02475002598.0199980396

5.50.00000316230.00000000320.10000315912.499921022199.99368196881.000003159124.999921022199.99936817890.01000315910.249921022199.93683764610.00100315910.024921022199.3701666398

6.00.0000010.000000010.100000992.4999752599.99802001961.0000009924.9999752599.99980200020.010000990.2499752599.980201960.001000990.0249752599.8021958261

6.50.00000031620.00000003160.10000028462.499992884999.99943079161.000000284624.999992884999.9999430790.01000028460.249992884999.99430806220.00100028460.024992884999.9430951975

7.00.00000010.00000010.12.51001251000.010.251000.0010.025100

7.50.00000003160.00000031620.09999971542.5000071151100.00056921160.999999715425.0000071151100.0000569210.00999971540.2500071151100.00569226180.00099971540.0250071151100.0569372025

8.00.000000010.0000010.099999012.50002475100.00198001960.9999990125.00002475100.00019800020.009999010.25002475100.01980196040.000999010.02502475100.1981962143

8.50.00000000320.00000316230.09999684092.5000789779100.00631843040.999996840925.0000789779100.00063182510.00999684090.2500789779100.0632022740.00099684090.0250789779100.6338254041

9.00.0000000010.000010.0999900012.500249975100.01999999980.99999000125.000249975100.001999820.0099900010.250249975100.20018016010.0009900010.025249975102.0199979596

9.50.00000000030.00003162280.09996837752.5007905615100.06326492670.999968377525.0007905615100.00632469210.00996837750.2507905615100.63445551190.00096837750.0257905615106.5310189631

10.00.00000000010.00010.09990000012.5024999975100.20019999980.999900000125.0024999975100.02000198020.00990000010.2524999975102.02019997960.00090000010.0274999975122.2221975309

10.500.00031622780.09968377232.5079056934100.6344618130.999683772325.0079056934100.06326555320.00968377230.2579056934106.53108573230.00068377230.0329056934192.4950455877

11.000.0010.0992.5249999998102.02020199980.99925.0249999998100.20020019820.0090.2749999998122.222221975300.049999999819999999900

11.500.00316227770.09683772232.5790569414106.53108640.996837722325.0790569414100.6344618760.00683772230.3290569414192.4950589796-0.00216227770.1040569414-192.4950592501

12.000.010.092.75122.22222221980.9925.25102.0202020200.51999999999900-0.0090.275-122.2222222247

12.500.03162277660.06837722343.290569415192.49505911350.968377223425.790569415106.5310864067-0.02162277661.040569415-192.4950591162-0.03062277660.815569415-106.5310864068

13.000.1051999722482756100.927.5122.2222222222-0.092.75-122.2222222222-0.0992.525-102.0202020202

13.500.316227766-0.21622776610.4056941504-192.49505911490.68377223432.9056941504192.4950591148-0.3062277668.1556941504-106.5310864067-0.3152277667.9306941504-100.6344618767

14.001-0.927.5-122.222222222205019999999999999900-0.9925.25-102.0202020202-0.99925.025-100.2002002002

Sheet1

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

000

000

000

000

00

00

00

00

0

0

0

0

%

pH

Sheet2

Sheet3

The Effect of Concentration

Indicator choice19.80 mL NaOHpH2-319.80 mL20.02 mLpH9.70-4.30=5.40.pKapH 4.30-9.70Fig 10-4

10C-2 The titration of a strong base with a strong acidsExample 10-2

1

13

12.5

12

11.5

11

10.5

10

9.5

9

8.5

8

7.5

7

6.5

6

5.5

5

4.5

4

3.5

3

2.5

2

1.5

1

%

pH

Sheet1

0.0010.997700063801.0977000638-22.4425015956-81.780086692913.9991.99770006380.05749840440.11512920381.0077000638-24.6925015956-98.01528245180.9987000638-24.9175015956-99.7997396744

0.10.50.31622776600.416227766-5.4056941504-51.949385329613.51.31622776617.094305849651.94938532960.326227766-7.6556941504-93.86931399370.317227766-7.8806941504-99.3695381633

0.11.00.100.200.0000000001131.122.581.81818181820.11-2.25-81.81818181820.101-2.475-98.0198019802

251.50.031622776600.13162277661.70943058551.9493853312.51.031622776624.20943058593.86931399370.0416227766-0.540569415-51.94938532920.0326227766-0.765569415-93.8693139936

12.00.0100.112.2581.8181818198121.0124.7598.01980198040.0200.0000000050.011-0.225-81.8181818165

12.50.003162277700.10316227772.420943058693.869313999611.51.003162277724.920943058699.3695381640.01316227770.170943058651.94938536610.0041622777-0.0540569414-51.9493852931

3.00.00100.1012.475000000298.0198019998111.00124.975000000299.80019980220.0110.225000000281.81818198350.0020.00000000020.0000005

3.50.000316227800.10031622772.492094306699.369538226210.51.000316227724.992094306699.93677444680.01031622770.242094306693.86931458790.00131622770.017094306651.9493889802

4.00.00010.00000000010.10009999992.497500002599.8001999998101.000099999924.997500002599.98000201980.01009999990.247500002598.01980394080.00109999990.022500002581.8181983471

4.50.00003162280.00000000030.10003162252.499209438599.93677507259.51.000031622524.999209438599.99367570790.01003162250.249209438599.36954444810.00103162250.024209438593.8693734213

5.00.000010.0000000010.1000099992.49975002599.980003999491.00000999924.99975002599.998000220.0100099990.24975002599.80021976030.0010099990.02475002598.0199980396

5.50.00000316230.00000000320.10000315912.499921022199.99368196888.51.000003159124.999921022199.99936817890.01000315910.249921022199.93683764610.00100315910.024921022199.3701666398

6.00.0000010.000000010.100000992.4999752599.998020019681.0000009924.9999752599.99980200020.010000990.2499752599.980201960.001000990.0249752599.8021958261

6.50.00000031620.00000003160.10000028462.499992884999.99943079167.51.000000284624.999992884999.9999430790.01000028460.249992884999.99430806220.00100028460.024992884999.9430951975

7.00.00000010.00000010.12.510071251000.010.251000.0010.025100

7.50.00000003160.00000031620.09999971542.5000071151100.00056921166.50.999999715425.0000071151100.0000569210.00999971540.2500071151100.00569226180.00099971540.0250071151100.0569372025

8.00.000000010.0000010.099999012.50002475100.001980019660.9999990125.00002475100.00019800020.009999010.25002475100.01980196040.000999010.02502475100.1981962143

8.50.00000000320.00000316230.09999684092.5000789779100.00631843045.50.999996840925.0000789779100.00063182510.00999684090.2500789779100.0632022740.00099684090.0250789779100.6338254041

9.00.0000000010.000010.0999900012.500249975100.019999999850.99999000125.000249975100.001999820.0099900010.250249975100.20018016010.0009900010.025249975102.0199979596

9.50.00000000030.00003162280.09996837752.5007905615100.06326492674.50.999968377525.0007905615100.00632469210.00996837750.2507905615100.63445551190.00096837750.0257905615106.5310189631

10.00.00000000010.00010.09990000012.5024999975100.200199999840.999900000125.0024999975100.02000198020.00990000010.2524999975102.02019997960.00090000010.0274999975122.2221975309

10.500.00031622780.09968377232.5079056934100.6344618133.50.999683772325.0079056934100.06326555320.00968377230.2579056934106.53108573230.00068377230.0329056934192.4950455877

11.000.0010.0992.5249999998102.020201999830.99925.0249999998100.20020019820.0090.2749999998122.222221975300.049999999819999999900

11.500.00316227770.09683772232.5790569414106.53108642.50.996837722325.0790569414100.6344618760.00683772230.3290569414192.4950589796-0.00216227770.1040569414-192.4950592501

12.000.010.092.75122.222222219820.9925.25102.0202020200.51999999999900-0.0090.275-122.2222222247

12.500.03162277660.06837722343.290569415192.49505911351.50.968377223425.790569415106.5310864067-0.02162277661.040569415-192.4950591162-0.03062277660.815569415-106.5310864068

13.000.10519997224827561010.927.5122.2222222222-0.092.75-122.2222222222-0.0992.525-102.0202020202

13.500.316227766-0.21622776610.4056941504-192.49505911490.50.68377223432.9056941504192.4950591148-0.3062277668.1556941504-106.5310864067-0.3152277667.9306941504-100.6344618767

14.001-0.927.5-122.2222222222005019999999999999900-0.9925.25-102.0202020202-0.99925.025-100.2002002002

Sheet1

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

000

000

000

000

00

00

00

00

0

0

0

0

%

pH

Sheet2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

%

pH

Sheet3

Sheet3

10.00123

1.50.52.53.5

2134

2.51.53.54.5

3245

3.52.54.55.5

4356

4.53.55.56.5

5467

5.54.56.57.5

6578

6.55.57.58.5

7689

7.56.58.59.5

87910

8.57.59.510.5

981011

9.58.510.5

10911

10.59.511.5

111012

11.510.5

1211

12.511.5

1312

12.5

13

13.5

14

10D Buffer solutionsA buffer solution is a solution of a conjugate acid/base pair that resists changes in pH.

pH12ca mol/L HB cb mol/L B- pHpH

Plots of pH vs. mL of water added to (a ) 0.500 mL of 0.100 molL-1 HCl and (b) 0.500 mL of a solution 0.100 molL-1 in both HAc and NaAc.pHHClNaAc-HAc

a)

pH

mL of Water

0

10

20

30

40

50

0

1

2

3

4

5

6

7

b)

pH

mL of Water

0

10

20

30

40

50

0

1

2

3

4

5

6

7

10D-1 Calculation of the pH of buffer solutionCa mol/L HB Cb mol/L B- H2O, HBPBEPBEH2O, B-1.pH < 6 2.pH > 83. CHACA-[H+][OH-]20

0.10 mol/L NH4HF20.10 mol/L NH4F + 0.10 mol/L HF NH4+HFF- 0.10 mol/L NH4HF2 pH

pHpH

10D-2 Properties of buffer solution1The effect of dilution2The effect of added acids and bases

Example 10-5pH

1 The definition of buffer capacity3. buffer capacityBuffer capacity is defined as the number of moles of strong acid or base required to change the pH of 1 L of buffer solution by one pH unit.

buffer capacity buffer index buffer intensity buffer value pHab

1pHdpHdbpHdpHdapH

HANaAcHAmol/L HA cA mol/L NaAc= cHA + cAHAH2OPBEbPBE

cKa[H+]HA/A=2.303 ([H+]+Ka)2 =2.303 cHAA- 0

d (Ka-[H+]) =2.303cKa =0 d[H+] (Ka+[H+])3 :max=2.303cKa2/(2Ka)2 =2.303 (c/4)=0.575c

HA=A-Ka=[H+] max=0.575c1.c2.1:1 1:13.HA/Aca:cb=1:10 10:11/3

1HF-F-pKa = 3.172HAc-Ac- pKa = 4.76C = 1.0 mol/LC = 0.5 mol/LC = 0.2 mol/L3H2PO4-HPO42- pKa2 = 7.214Na2B4O7 pKa = 9.185NH3-NH4+ pKa = 9.2467

pHpHab 1 50 mL0.10 molL-1 NH30.10 molL-1 NH4Cl3:1pH9.738.73pKa = 9.25b0 b0

20.10 molL-1 NH30.10molL-1 NH4Cl3:1 pKa = 9.25 = 0.043 molL-1 pH-1

41 0.034 molL KHTar(3.56); 0.05 molL-1 (4.01)0.025 molL-1 K2HPO4+0.025 molL-1 Na2HPO4(6.88); 0.01 molL-1(9.18)pH2 HAc-NaAc, NH3-NH4Cl512pH3

Preparation of buffers

A buffer solution of any desired pH can be prepared by combing calculated quantities of a suitable conjugate acid/base pair.

Prepared buffers by making up a solution of approximately the desired pH and than adjust by adding acid or conjugate base until the required pH is indicated by a pH meter.

-HCl +NH3CH2COOH +NH3CH2COO- 2.35(pKa1)-NaOH CHClCOOH CHClCOO- 2.86-NaOH HCOOH HCOO- 3.76HAc-NaAc HAc Ac- 4.74-HCl (CH2) 6N4H+ (CH2)6N4 5.15NaH2PO4-Na2HPO4 H2PO4- HPO42- 7.20(pKa2)Na2B4O7-HCl H3BO3 H2BO3- 9.24(pKa1)Na2B4O7-NaOH H3BO3 H2BO3- 9.24(pKa1)NH3-NH4Cl NH4 + NH3 9.26 -NaOH +NH3CH2COO- NH2CH2COO- 9.60(pKa2)NaHCO3-Na2CO3 HCO3- CO3 10.25(pKa2)

10E Titration curves for weak acids1At the beginning, the solution contains only the solute acid or base, and the pH is calculated from the concentration of that solute and its dissociation constant.2After various increments of titrant have been added, the solution consists of a series buffers. The pH each buffer can be calculated from the analytical concentration of the conjugate base or acid and the residual concentration of the weak acid or base.

3At the equivalence point, the solution contains only the conjugate of the weak acid or base being titrated that is , a salt, and the pH is calculated from the concentration of this product.4Beyond the equivalence point, the excess of strong acid or base titrant represses the acidic or basic character of the reaction product to such an extent that the pH is governed largely by the concentration of the excess titrant.

Example 10-6 NaOH Titrated HAc

0.1000 molL-1 NaOH 20.00 mL Ca0.1000 molL-1 HA ca molL-1 , cb molL-1 b molL-1

PBE[H+] HA[H+] = [OH-] + [A]HA-A-[H+] + cb = [OH-] + [A]A-[H+] + [HA] = [OH-]A-+OH-[H+] + b +[HA] = [OH-] [OH-] = b

HAcHCl

3

3.0011.001

3.2011.201

3.4011.401

3.6011.601

3.8011.801

4.0012.001

4.2012.201

4.4012.401

4.6012.601

4.8012.801

5.0013.001

5.2013.201

5.4013.401

5.6013.601

5.8013.801

6.0014.001

6.2014.201

6.4014.401

6.6014.601

6.8014.801

7.0015.001

7.2015.201

7.4015.401

7.6015.601

7.8015.801

8.0016.001

8.2016.201

8.4016.401

8.6016.601

8.8016.801

9.0017.001

9.2017.201

9.4017.401

9.6017.601

9.8017.801

10.0018.001

10.2018.201

10.4018.401

10.6018.601

10.8018.801

11.0019.001

11.2019.201

11.4019.401

11.6019.601

11.8019.801

12.00110.001

12.20110.201

12.40110.401

12.60110.601

12.80110.801

11.001

11.201

11.401

11.601

11.801

12.001

12.201

12.401

12.601

12.801

%

pH

Sheet1

0.00001778280.0010.99770006380.00000178230-0.99769828151.0977000638-90.8898809754-0.8977000638-81.7800866929

0.10.2010.62950618290.00000282480-0.62950335810.7295061829-86.2917097689-0.5295061829-72.5841939795

0.4010.39719154950.00000447690-0.39718707250.4971915495-79.8861269788-0.2971915495-59.774054846

0.6010.25061092530.00000709530-0.250603830.3506109253-71.4763322941-0.1506109253-42.9567119658

0.8010.15812480390.00001124480-0.15811355910.2581248039-61.2546941388-0.0581248039-22.5181009507

1.0010.09977000640.00001782060-0.09975218580.1997700064-49.9335148340.00022999360.1151292038

1.2010.06295061830.00002824080-0.06292237750.1629506183-38.61438399280.037049381722.7365701979

1.4010.03971915490.00004475130-0.03967440370.1397191549-28.39582279690.060280845143.1442954807

1.6010.02506109250.00007090750-0.02499018510.1250610925-19.98238185990.074938907559.9218397618

1.8010.01581248040.00011233420-0.01570014620.1158124804-13.55652359150.084187519672.6929596214

2.0010.00997700060.00017792080-0.00979907990.1099770006-8.91011741170.090022999481.856205244

2.2010.00629506180.00028169230-0.00601336960.1062950618-5.65724265350.093704938288.1554952436

2.4010.00397191550.00044571780-0.00352619770.1039719155-3.39149058570.096028084592.3596377476

2.6010.00250610930.00070457820-0.0018015310.1025061092-1.75748648040.097493890895.1103221703

2.8010.0015812480.00111209830-0.00046914980.101581248-0.46184682750.09841875296.8867324165

3.0010.00099770010.001751166400.00075346630.10099770010.74602322230.099002299998.0243113392

3.2010.00062950620.002747272800.00211776660.10062950622.10451857410.099370493898.7488636466

3.4010.00039719150.004285275600.0038880840.10039719153.87270198570.099602808599.2087596909

3.6010.00025061090.006625637200.00637502630.10025061096.3590897380.099749389199.5000312054

3.8010.00015812480.01010916770.00000000010.0099510430.10015812479.93533275080.099841875399.6842497978

4.0010.000099770.01512749510.00000000010.01502772520.100099769915.01274696260.099900230199.80065907

4.2010.00006295060.02202656070.00000000020.02196361030.100062950521.9497927650.099937049599.8741782865

4.4010.00003971920.03092555020.00000000030.03088583130.100039718930.87356862230.099960281199.9205937329

4.6010.00002506110.04150602450.00000000040.04148096390.100025060741.47057103740.099974939399.9498911706

4.8010.00001581250.05293242690.00000000060.0529166150.100015811852.90824924280.099984188299.9683813035

5.0010.0000099770.06405953020.0000000010.06404955420.10000997664.04316527940.09999002499.9800499935

5.2010.00000629510.07385538880.00000000160.07384909530.100006293573.84444790190.099993706599.9874138455

5.4010.00000397190.0817422730.00000000250.08173830360.100003969481.73505917950.099996030699.9920615195

5.6010.00000250610.08764788210.0000000040.087645380.100002502187.64318709250.099997497999.9949958872

5.8010.00000158120.09183410140.00000000630.09183252650.100001574991.83108024110.099998425199.9968502018

6.0010.00000099770.09468757290.000000010.09468658520.100000987794.68565002220.099999012399.9980246655

6.2010.00000062950.09658105630.00000001590.09658044270.100000613696.57985003280.099999386499.9987727661

6.4010.00000039720.09781522630.00000002520.09781485430.10000037297.81449037710.09999962899.9992559732

6.6010.00000025060.09861029610.00000003990.09861008540.100000210798.60987765460.099999789399.999578584

6.8010.00000015810.0991186360.00000006320.09911854110.100000094999.11844705010.099999905199.9998102329

7.0010.00000009980.09944208220.00000010020.09944208270.099999999599.44208312890.1000000005100.000000921

7.2010.0000000630.09964725140.00000015890.09964734730.099999904199.64744284960.1000000959100.0001918083

7.4010.00000003970.09977714060.00000025180.09977735260.09999978899.77756417580.100000212100.000424098

7.6010.00000002510.09985926950.0000003990.09985964340.09999962699.86001685430.100000374100.0007479304

7.8010.00000001580.09991115890.00000063240.09991177550.099999383499.91239154440.1000006166100.0012332063

8.0010.000000010.09994392670.00000100230.0999449190.099999007799.9459107820.1000009923100.0019846762

8.2010.00000000630.09996461280.00000158850.0999661950.099998417799.96777678640.1000015823100.0031645534

8.4010.0000000040.09997766930.00000251770.0999801830.099997486399.98269624060.1000025137100.0050275364

8.6010.00000000250.09998590910.00000399020.09998989680.099996012399.99388433980.1000039877100.0079758039

8.8010.00000000160.09999110880.00000632410.09999743130.0999936775100.00375409130.1000063225100.0126458741

9.0010.0000000010.09999438980.00001002310.10000441190.0999899779100.01443539110.1000100221100.0200461184

9.2010.00000000060.09999646020.00001588550.1000123450.0999841152100.02823431280.1000158848100.0317747233

9.4010.00000000040.09999776650.00002517680.10002294280.0999748236100.04813133960.1000251764100.0503654244

9.6010.00000000030.09999859070.00003990250.1000384930.0999600978100.07842650420.1000399022100.0798363357

9.8010.00000000020.09999911080.00006324120.10006235180.099936759100.12567233730.100063241100.1265620932

10.0010.00000000010.0999994390.00010023050.10009966940.0998997696100.20010036470.1001002304100.2006619724

10.2010.00000000010.0999996460.00015885470.10015850060.0998411454100.31786016330.1001588546100.3182147226

10.40100.09999977660.00025176770.10025154430.0997482323100.50458232450.1002517677100.5048062449

10.60100.09999985910.00039902490.10039888390.0996009751100.80110543590.1003990249100.8012469292

10.80100.09999991110.00063241190.10063232290.0993675882101.27278398770.1006324118101.2728734736

11.00100.09999994390.00100230520.10100224910.0989976948102.02484952410.1010023052102.0249061969

11.20100.09999996460.00158854670.10158851130.0984114533103.22834180340.1015885467103.2283777746

11.40100.09999997770.00251767690.10251765460.0974823231105.16537906870.1025176769105.1654019813

11.60100.09999998590.0039902490.10399023490.096009751108.31215982540.103990249108.312174504

11.80100.09999999110.00632411850.10632410960.0936758815113.50211808150.1063241185113.5021275738

12.00100.09999999440.01002305240.11002304680.0899769476122.2791500260.1100230524122.2791562614

12.20100.09999999650.01588546750.11588546390.0841145325137.77103727610.1158854675137.7710414846

12.40100.09999999780.02517676930.1251767670.0748232307167.29666152390.1251767693167.2966645091

12.60100.09999999860.03990249020.13990248880.0600975098232.79248903320.1399024902232.7924913782

12.80100.09999999910.06324118510.16324118420.0367588149444.08717979270.1632411851444.0871822117

13.00100.09999999940.10023052380.2002305232-0.0002305238-86858.93455227280.2002305238-86858.9347956525

13.20100.09999999960.15885467490.2588546745-0.0588546749-439.8200739750.2588546749-439.8200745765

13.40100.09999999980.25176769280.3517676926-0.1517676928-231.78035200950.3517676928-231.7803521566

13.60100.09999999990.39902490240.4990249022-0.2990249024-166.88406158790.4990249024-166.884061635

13.80100.09999999990.63241185140.7324118513-0.5324118514-137.56490382290.7324118514-137.5649038396

14.00100.09999999991.00230523811.102305238-0.9023052381-122.16544817691.1023052381-122.1654481832

Sheet1

%

pH

Sheet2

Sheet3

0.1000 mol/L NaOH0.1000 mol/L HAc (1)

(2) NaOH19.98 ml,

(3) NaAc

(4) 20.02 mL NaOH

titration jump 7.74-9.70

12pHAc-HpHpH ( 3 ) Ac-HAcpH4pH56

10E-1 The effect of concentration

KaKaKa

10E-3 Indicator choice; The Feasibility of titrationpH>0.20.1%, :cka>108 Indicator choice(1)pHep=pHsp(2)pH

10F Titration curves for weak bases11

2

3

4 [H+] = c 2 3 ckb > 108Example 10-7HCl Titrated NaCN

10H Common types of acid/base indications10H-1 Common indicator structures10H-2 Titration error with acid/base indicators10H-3 Variable that influence the behavior of indicators

(titration error)

()NaOHHCl

csp,VspVnp Vnp Vsp

cNaOH-cHCl= [OH-] - [H+]

0.1000 mol/LNaOH25.00 mL 0.1000 mol/L HClpH=4

csp=0.05000 mol/L, pH=4, [H+]=10-4 mol/L

pH=9cb=0.05000 mol/L, pH=9, [H+]=10-9 mol/L[OH-]=10-14/10-9=10-5 mol/L

()NaOHHA [H+]+cNaOH=[A-]+[OH-]=cHA-[HA]-[OH-] cNaOH- cHA = [OH-]- [HA]- [H+]

[H+][HA]/cSP=HA csp=c0V0/Vep, c0, V0 Vep

0.1000 mol/L NaOH0.1000 mol/L HAc pH0.50.5

pH=8.73pH0.5pH9.23[H+]=5.910-10 mol/L[OH-]=1.7 10-5 mol/LcSP=0.1000/2=0.0500 mol/L

pH0.5pH8.23[H+]=5.910-9 mol/L[OH-]=1.7 10-6 mol/LcSP=0.1000/2=0.0500 mol/L

Titration curves for complex acid/base system11A Mixtures of strong and weak acids or strong and weak bases

Example 11-1(a) 0.00mL KOH PBE[H+]=[OH-]+cHCl+[A-]=cHCl+[A-] HA[H+ ]=(Kac)1/2= 2.810-3 mol/L, 0.12 mol/L HCl[A-]

The [H+] is simply the molar concentration of the strong acid. [H+]=caThe approximation employed can be shown to apply until most of the HCl has been neutralized by the titrant.The curve in this region is identical to the titration for a 0.1200 mol/L solution of a strong acid by itselfHCl

(b)added 29.00 mL 0.1000 mol/L KOH (Example 11-2) cHCl=1.8510-3 mol/L, cHA=3.7010-2 mol/L ,

pH=2.52

(c) the first equivalence point HA calculated the [H+](d) the second equivalence point NaA calculated the [H+]HAHClHAHAKa10-410-8Fig.11-1

11B Polyfunctional acids11C Polyfunctional bases11E calculation of the pH of solutions of amphiprotic salts

11D Buffer solutions involving polyprotic acidspHExample 11-3H3PO4/NaH2PO4Example 11-4KHP/K2P

12pHsp311F Titration curves for polyfunctional acids

Ka1, Ka210-2, 10-910-2, 10-710-2, 10-50.1000 molL-1 NaOHcKa1 10-8, cKa2 10-8, Ka1 / Ka2 10 5HA- A2-cKa1 10-8, cKa2

pHsp0.1000 molL-1 NaOH0.1000 molL-1 H3PO4, H3PO4 pKa1 = 2.16 pKa2 = 7.21 , pKa3 = 12.32 H2PO4- pH = 4.70 HPO42- pH = 9.66

pH

NaOH HA HB CHA, CHB, K a, HA > K a, HB(1) CHAK a, HA 10-8, CHAK a, HA / CHB K a, HB 105 A-HB , (2) CHAK a, HA 10-8, CHBK a, HB 10-8, CHAK a, HA / CHB K a, HB 105 A- B- ,

(3) CHAK a, HA 10-8, CHBK a, HB 10-8, CHAK a, HA / CHB K a, HB 105HA HB

KaKb1B4O72- + 5H2O = 2H3BO3 + 2H2BO3- Kb=Kw/Ka=1.7210-5 H2BO3- H+ H3BO3 B4O72- + 5H2O 2H+ 4H3BO311G Titration curves for polyfunctional bases

2Equivalence point pH 0.05 mol/L0.1000 mol/L HCl 20.00 mL4

pH = 5.123Indicator

Na2CO3 titrated1Reaction CO32- + H+ HCO3- Kb1 = 1.7910-4 HCO3- + H+ = H2CO3 Kb2 = 2.3810-82differentiate condition 105Kb2

3Equivalence points pH First equivalence point HCO3 pH = 8.31 Sencond equivalence H2CO3

pH = 3.89 C:0.04 mol/L 4Indicator First equivalence point :PP Second MO

CO2H2CO3CO2CO2

HClNa2CO3pHsp1 =8.3 PPpHsp2 =3.9 MO

C 10-4 mol/L Cka 10-8 Ckb 10-8NaHA Cka2 10-8NaHA Ckb2 10-8 Ka 105 Kb 105 C1Ka1/C2ka2 104-5

11H Titration curves for amphiprotic species11I The composition of solutions of a polyprotic acid as a function of pH

Applications of neutralization titrations12A Reagents for neutralization titrations12A-1 Preparation of standard acid solution HCl, HClO4, H2SO4, HNO3Constant-boiling HCl HClIndirect prepare Standard acid solution are ordinarily prepared by diluting an approximate volume of the concentrated reagent and subsequently standardizing the diluted solution against a primary-standard base.

12A-2 The standardization of acidsNa2CO3, Na2B4O7Example 12-10.020 mol/L HCl30 mLExample 12-20.1mg

12A-3 Preparation of standard solution of bases The effect of carbon dioxide upon standard base solutions 1CO2(1) distilled water dissolve CO2(2) basic solvent absorb CO2(3) absorb CO2 in reserve of basic standard solution(4) absorb CO2 in titration

2Effect of CO2 (1)CO2 pHpH < 5.0 CO2H2CO3pH > 5.0 CO2HCO3-CO32-

(2)CO2pHPPpH8.0HCO3-CO2MOpH4.0H2CO3CO2

NaOH CO2 HClNaOH H2CO3CO2 2H+HCO3- 1 H+H2CO3 2H+pKa1 = 6.38 pKa2 = 10.25 ,2H2O

> 0.1 mol / LCO2 CO2

Example 12-3 CO2NaOHHAcPPHCO3-1OH-NaOHCO22OH-Na2CO3,NaOH0.05118 mol/L 0.05118-0.1962/44.01=0.04672Er-8.7%.

3Derated CO2 1CO22CO32350NaOHNa2CO34Ba(OH)2Ca(OH)2, BaCO3CaCO35NaOH 6CO27

The solid reagent used to prepare standard solutions of base are always contaminated by significant amounts of carbonate ion. The presence of this contaminant does not cause a carbonate error provided the same indicator is used for both standardization and analysis.

Conservation of baseThe concentration of a sodium hydroxide solution will decrease slowly (0.1%-0.3% per week) if the base is stored in glass bottles.12A- 4 The standardization of base KHC8H4O4Other primary standards for baseKH(IO3)2

BaCl2 (

NaOH + Na2CO3Na2CO3 + NaHCO3NaH2PO4 + Na2HPO4Na3PO4 + Na2HPO4Na3PO4 + NaOHH3PO4 + HClH2PO4- + H3PO4 HPO42- + H2PO4-

1BaCl2 1NaOH Na2CO3 V1V2NaOHNa2CO3H2CO3 V2V

BaCl2 NaOHNa2CO3NaOHNa2CO3H2O

2NaHCO3 Na2CO3 3 NaOHNaHCO3 Na2CO3 NaOHNa2CO3NaHCO3

V2V

12345NaOHNa2CO3NaHCO3NaOH-Na2CO3Na2CO3-NaHCO3V1 > 0V1 > 0V1 = 0V1 > 0V1 > 0V2 = 0V2 > 0V2 > 0V2 > 0V2 > 0V1 = V2V1 > V2V1 < V2

2HClH3PO4H2PO4-

3NH4+NH4+NH3HCl H3BO3 HCl NH3NH4Cl + HCl H2O + NH4+pH 5

H3BO3 NH3NH4Cl + H2BO3- NH3 + H3BO3 H3BO3 + NH4+pKb = 4.76pH 5

16 % 6.256.27.

0.2500g 0.1000 mol / L HCl 21.20 ml6.25HCl

45

12B Typical applications of neutralization titrations12B-1 Elemental analysis12B-3 The determination of organic functional group

10-18 11-10 12-1710-20 11-11 12-3110-22 11-20 12-3510-32 12-4010-34 12-44