Chapter 26: Q49 P (page 750)

To obtain the best separation of two weak acids in capillary electrophoresis, it makes sense to use the pH at which their charge difference is greatest. Prepare a spreadsheet to examine the charges of malonic and phthalic acid as a function of pH. At what pH is the difference greatest?

Short Answer

Expert verified

The greatest value of pH = 5.55

Step by step solution

Define Function of pH

PH is the measure of how acidic or basic a substance is. In humans, pH balance plays a role in keeping the body functioning optimally. The ideal pH of the body is slightly alkaline, which facilitates certain biochemical reactions like oxygenating the blood.

Malonic and phthalic acid

Malonic

$α$

av.charge

charge

K1 =

$[H^{+}]$

$[H M^{-}]$

$M^{2 -}$

$H P^{-}$

$P^{2 -}$

malonate

phtalate

difference

1.42E - 03

5.52

3.0E - 06

0.600

0.399

0.436

0.563

-1.398

- 1.562

- 0.1639

K2 =

5.53

3.0E - 06

0.594

0.405

0.430

0.569

- 1.403

- 1.567

- 0.1640

2.01E - 06

5.54

2.9E - 06

0.589

0.410

0.425

0.574

- 1.409

- 1.573

- 0.1641

phthalic

5.55

2.8E - 06

0.583

0.416

0.419

0.580

- 1.415

- 1.579

- 0.1642

K1 =

5.56

2.8E - 06

0.577

0.421

0.413

0.585

- 1.420

- 1.584

- 0.1642

1.12E - 03

5.57

2.7E - 06

0.572

0.427

0.408

0.591

- 1.426

- 1.590

- 0.1641

K2 =

5.58

2.6E - 06

0.566

0.433

0.402

0.597

- 1.432

- 1.596

- 0.1640

3.90E - 06

5.59

2.6E - 06

0.561

0.438

0.397

0.602

- 1.437

- 1.601

- 0.1639

Maximum difference

From spreadsheet, the greatest value of pH = 5.55

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To obtain the best separation of two weak acids in capillary electrophoresis, it makes sense to use the pH at which their charge difference is greatest. Prepare a spreadsheet to examine the charges of malonic and phthalic acid as a function of pH. At what pH is the difference greatest?

Short Answer

Step by step solution

Define Function of pH

Malonic and phthalic acid

Maximum difference

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