/
Titration of a weak acid Titration of a weak acid

Titration of a weak acid - PowerPoint Presentation

alexa-scheidler
alexa-scheidler . @alexa-scheidler
Follow
466 views
Uploaded On 2016-09-07

Titration of a weak acid - PPT Presentation

acetic acid CH 3 COOH pKa 48 10 08 06 02 04 OH equivalents pH A H A H A HA 1 1000 pH 18 pK a 30 Titration of a weak acid acetic acid CH ID: 462009

acid pka titration weak pka acid weak titration acidacetic ch3cooh equivalents charge 1000 state acidic 100 acids unit region

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document "Titration of a weak acid" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

A

H

A

-

H

+

[A

-

]

: [HA] = 1 : 1000

pH:

1.8

=

pK

a

–3.0Slide2

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

2.8

=

pK

a

–2.0

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 100

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide3

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

3.8

=

pK

a

–1.0

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 10

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide4

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

4.2

=

pK

a

–0.6

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 4

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide5

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

4.4

=

pK

a

–0.4

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 2.3

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide6

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

4.6

=

pK

a

–0.2

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 1.5

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide7

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

4.8

=

pK

a

A

H

A

-

H

+

[A

-

] : [HA] = 1 : 1

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide8

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

5.8

= pK

a

+1.0

A

H

A

-

H

+

[A

-

] : [HA] = 10: 1

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide9

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

6.8

= pK

a

+2.0

A

H

A

-

H

+

[A

-

] : [HA] = 100: 1

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide10

Titration of a weak acidacetic acid, CH3COOH, pKa = 4.8

1.0

0.8

0.6

0.2

0.4

OH

-

equivalents

pH:

7.8

= pK

a

+3.0

A

H

A

-

H

+

[A

-

] : [HA] = 1000: 1

OH

-

+ HA

H

2

O + A

-

OH

-

+ H

+

H

2

OSlide11

~80% of acid dissociation occurs within1 pH unit of pKa

OH- eq. added

pH

= pKa + ___

[A-] : [HA]0.01.8-3.0

1:1000~0.012.8

-2.01:1000.13.8

-1.0

1:100.24.2

-0.61:40.34.4

-0.41:2.30.4

4.6-0.21:1.5

0.54.80.01:1

0.65.00.2

1.5:10.75.2

0.42.3:10.8

5.40.64:1

0.95.81.0

10:1~0.996.8

2.0100:11.0

7.83.01000:1Slide12

In this buffering region (±1 pH unit of

pKa

), dissociation of the weak acid slows the rise in pHSlide13

Titration of other acids gives the same curve, just shifted along the pH axis (based on

pKa

)Slide14

Some weak acids (like amino acids) are

polyprotic

and can buffer over multiple pH ranges

With 2 acidic groups, there are 3 charge states

Isoelectric point (

pI):pH of highest occurrence of zero charge stateand

pH at which average charge on molecules is zeroFor simple cases,pI = (pKai

+ pKaj

)/2Slide15

With 3 acidic groups, there are 4 charge states

The amino acid glutamate has an acidic R group

To calculate

pI

, use

pKa’s that relate to neutral charge state

Neutral charge state predominates in this region of titration

pI

= (pK

1 + pKR)/2= 3.22