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Acid/Base Titrations

Date post: 16-Jan-2016
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Acid/Base Titrations. Titrations. Titration Curve – always calculate equivalent point first Strong Acid/Strong Base Regions that require “different” calculations B/F any base is added Half-way point region At the equivalence point After the equivalence point. Strong Acid/Strong Base. - PowerPoint PPT Presentation
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Acid/Base Titrations Acid/Base Titrations
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Page 1: Acid/Base Titrations

Acid/Base TitrationsAcid/Base Titrations

Page 2: Acid/Base Titrations

Titrations Titration Curve – always calculate

equivalent point first Strong Acid/Strong Base

Regions that require “different” calculations B/F any base is added Half-way point region At the equivalence point After the equivalence point

Page 3: Acid/Base Titrations

Strong Acid/Strong Base 50 mL of 0.02000 M KOH Titrated with 0.1000 M HBr

First -find Volume at equivalence M1V1 = M2V2

(0.050 L)(0.02000M) = 0.1000 V V = 10.0 mL

Page 4: Acid/Base Titrations

Strong Acid/Strong Base 50.00 mL of 0.02000 M KOH Titrated with 0.1000 M HBr

Second – find initial pH pH = - logAH ~ -log [H+]

pOH = -logAOH ~ -log [OH-]

pH = 12.30

Page 5: Acid/Base Titrations

Strong Acid/Strong Base 50 mL of 0.02000 M KOH Titrated with 0.1000 M HBr

Third– find pH at mid-way volume KOH (aq) + HBr (aq) -> H2O (l) +

KBr(aq) BeforeAfter

0.001000 mol 0.0006000 mol0.000400 mol 0 mol

Limiting Reactant

0.0006000 mol0.0006000 mol

pH = 11.8

(~6 ml)

Page 6: Acid/Base Titrations

Strong Acid/Strong Base 50 mL of 0.02000 M KOH Titrated with 0.1000 M HBr

Fourth – find pH at equivalence point KOH (aq) + HBr (aq) -> H2O (l) + KBr(aq)

BeforeAfter

0.001000 mol 0.0010000 mol0 mol 0 mol 0.0010000 mol0.0010000 mol

pH = 7.0

Page 7: Acid/Base Titrations

Strong Acid/Strong Base 50 mL of 0.02000 M KOH Titrated with 0.1000 M HBr

Finally – find pH after equivalence point KOH (aq) + HBr (aq) -> H2O (l) + KBr(aq)

BeforeAfter

0.001000 mol 0.001200 mol0 mol 0.0002000 mol 0.0010000 mol

pH = 2.5

12 ml

Limiting Reactant

Page 8: Acid/Base Titrations

Typical pH titration

0

2

4

6

8

10

12

14

0 5 10 15 20

mL of HBr

pH

Page 9: Acid/Base Titrations
Page 10: Acid/Base Titrations

Titration of WEAK acid with a strong base

Page 11: Acid/Base Titrations
Page 12: Acid/Base Titrations

Titration of a weak acid solution with a strong base.

25.0 mL of 0.1000M acetic acid Ka = 1.8 x 10-5 Titrant = 0.100 M NaOH

First, calculate the volume at the equivalence-point M1V1 = M2V2

(0.0250 L) 0.1000 M = 0.1000 M (V2) V2 = 0.0250 L or 25.0 mL

Page 13: Acid/Base Titrations

Titration of a weak acid solution with a strong base.

25.0 mL of 0.1000M acetic acid Ka = 1.8 x 10-5 Titrant = 0.100 M NaOH

Second, Calculate the initial pH of the acetic acid solution

Page 14: Acid/Base Titrations

Titration of a weak acid solution with a strong base.

25.0 mL of 0.1000M acetic acid Ka = 1.8 x 10-5 Titrant = 0.100 M NaOH

Third, Calculate the pH at some intermediate volume

Page 15: Acid/Base Titrations

Titration of a weak acid solution with a strong base.

25.0 mL of 0.1000M acetic acid Ka = 1.8 x 10-5 Titrant = 0.100 M NaOH

Fourth, Calculate the pH at equivalence

Page 16: Acid/Base Titrations

Titration of a weak acid solution with a strong base.

25.0 mL of 0.1000M acetic acid Ka = 1.8 x 10-5 Titrant = 0.100 M NaOH

Finally calculate the pH after the addition 26.0 mL of NaOH

Page 17: Acid/Base Titrations
Page 18: Acid/Base Titrations

0

2

4

6

8

10

12

14

0 10 20 30 40 50

Volume of NaOH, mL

pH

Initial pH

aa CKH ][

Buffer Region

][

][log

acid

basepKpH a

Equivalence pointM1V1=M2V2

pH @ equivalence?

pH after equivalence?

Page 19: Acid/Base Titrations

0

2

4

6

8

10

12

14

0 10 20 30 40 50

Volume of NaOH, mL

pH

Initial pH

aa CKH ][

Buffer Region

][

][log

acid

basepKpH a

Equivalence pointM1V1=M2V2

pH @ equivalence

pH after equivalence?

bb CKOH ][

Page 20: Acid/Base Titrations

0

2

4

6

8

10

12

14

0 10 20 30 40 50

Volume of NaOH, mL

pH

Initial pH

aa CKH ][

Buffer Region

][

][log

acid

basepKpH a

Equivalence pointM1V1=M2V2

pH @ equivalence

pH after equivalenceDominated by remaining[OH-]

bb CKOH ][

Page 21: Acid/Base Titrations
Page 22: Acid/Base Titrations

Weak Base titrated with strong acid Consider a 100 ml of a 0.0100 M

base with 0.0500 M HCl Kb = 1 x 10-5

Page 23: Acid/Base Titrations

Initial pH

bb CKOH ][

Buffer Region

][

][log

acid

basepKpH a

pH @ equivalence

aa CKH ][

pH after equivalenceDominated by remaining[H+]

Page 24: Acid/Base Titrations

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