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CHM 112
Section 1

Homework Assignment #14
Due March 3, 2006 by 8:05 a.m.

Practice (not to be turned in): Review Question 15.5

A solution of an unknown acid is prepared with a concentration of 0.00148 M. After equilibrium is attained, the solution was found to have a per cent ionization equal to the last four digits of your Student ID Number divided by 103 ( = Last4ID/103 %). Calculate the Ka and pKa for the unknown acid.



Answers:

 

HA(aq)

+

H2O(l)

H3O+(aq)

+

A(aq)

 

Initial

0.00148

     

0

 

0

Change

-x

     

+x

 

+x

Equilibrium

0.00148 - x

     

x

 

x

x is found from the per cent ionization: x = ×0.00148/100%

Then, the equilibrium constant is found by substituting into the mass action expression for Ka = x2/(0.00148–x)

pKa = -logKa, found to 2 places past the decimal.

Specific answers:

Student ID Number

per cent ionization

x

Ka

pKa

100006330

6.33

9.37×10–5

6.3×10–6

5.20

100008852

8.852

1.31×10–4

1.3×10–5

4.90

100009388

9.388

1.39×10–4

1.4×10–5

4.84

100010785

0.785

1.16×10–5

9.2×10–8

7.04

100017560

7.56

1.12×10–4

9.2×10–6

5.04

100046288

6.288

9.31×10–5

6.2×10–6

5.20

100064823

4.823

7.14×10–5

3.6×10–6

5.44

100077590

7.59

1.12×10–4

9.2×10–6

5.03

100105142

5.142

7.61×10–5

4.1×10–6

5.38

100143544

3.544

5.25×10–5

1.9×10–6

5.72

100148294

8.294

1.23×10–4

1.1×10–5

4.95

100160251

0.251

3.71×10–6

9.3×10–9

8.03

100164496

4.496

6.65×10–5

3.1×10–6

5.50

100168422

8.422

1.25×10–4

1.1×10–5

4.94

100170841

0.841

1.24×10–5

1.1×10–7

6.98

100173015

3.015

4.46×10–5

1.4×10–6

5.86

100173826

3.826

5.66×10–5

2.3×10–6

5.65

100173947

3.947

5.84×10–5

2.4×10–6

5.62

100175807

5.807

8.59×10–5

5.3×10–6

5.28

100176275

6.275

9.29×10–5

6.2×10–6

5.21

100180084

0.084

1.24×10–6

1.0×10–9

8.98

100180208

0.208

3.08×10–6

6.4×10–9

8.19

100187549

7.549

1.12×10–4

9.1×10–6

5.04

100188349

8.349

1.24×10–4

1.1×10–5

4.95

100192352

2.352

3.48×10–5

8.4×10–7

6.08

100193608

3.608

5.34×10–5

2.0×10–6

5.70

100193957

3.957

5.86×10–5

2.4×10–6

5.62

100194186

4.186

6.20×10–5

2.7×10–6

5.57

100194417

4.417

6.54×10–5

3.0×10–6

5.52

100195646

5.646

8.36×10–5

5.0×10–6

5.30

100196467

6.467

9.57×10–5

6.6×10–6

5.18

100197351

7.351

1.09×10–4

8.6×10–6

5.06

100197396

7.396

1.09×10–4

8.7×10–6

5.06

100200053

0.053

7.84×10–7

4.2E-10

9.38

100201157

1.157

1.71×10–5

2.0×10–7

6.70

100203271

3.271

4.84×10–5

1.6×10–6

5.79

100205446

5.446

8.06×10–5

4.6×10–6

5.33

100205601

5.601

8.29×10–5

4.9×10–6

5.31

100207237

7.237

1.07×10–4

8.4×10–6

5.08

100210253

0.253

3.74×10–6

9.5×10–9

8.02

100210303

0.303

4.48×10–6

1.4×10–8

7.87

100212014

2.014

2.98×10–5

6.1×10–7

6.21

100212080

2.08

3.08×10–5

6.5×10–7

6.18

100212092

2.092

3.10×10–5

6.6×10–7

6.18

100212152

2.152

3.18×10–5

7.0×10–7

6.15

100212510

2.51

3.71×10–5

9.6×10–7

6.02

100213402

3.402

5.03×10–5

1.8×10–6

5.75

100214888

4.888

7.23×10–5

3.7×10–6

5.43

100215062

5.062

7.49×10–5

4.0×10–6

5.40

100215125

5.125

7.59×10–5

4.1×10–6

5.39

100215264

5.264

7.79×10–5

4.3×10–6

5.36

100215471

5.471

8.10×10–5

4.7×10–6

5.33

100216695

6.695

9.91×10–5

7.1×10–6

5.15

100216822

6.822

1.01×10–4

7.4×10–6

5.13

100217841

7.841

1.16×10–4

9.9×10–6

5.01

100218709

8.709

1.29×10–4

1.2×10–5

4.91

100218865

8.865

1.31×10–4

1.3×10–5

4.89

100218867

8.867

1.31×10–4

1.3×10–5

4.89

100218981

8.981

1.33×10–4

1.3×10–5

4.88

100219014

9.014

1.33×10–4

1.3×10–5

4.88

100219019

9.019

1.33×10–4

1.3×10–5

4.88

100219138

9.138

1.35×10–4

1.4×10–5

4.87

100219323

9.323

1.38×10–4

1.4×10–5

4.85

100219636

9.636

1.43×10–4

1.5×10–5

4.82

100219715

9.715

1.44×10–4

1.5×10–5

4.81

100219950

9.95

1.47×10–4

1.6×10–5

4.79

100220082

0.082

1.21×10–6

1.0×10–9

9.00

100220712

0.712

1.05×10–5

7.6×10–8

7.12

100220848

0.848

1.26×10–5

1.1×10–7

6.97

100220947

0.947

1.40×10–5

1.3×10–7

6.87

100221065

1.065

1.58×10–5

1.7×10–7

6.77

100221836

1.836

2.72×10–5

5.1×10–7

6.29

100222238

2.238

3.31×10–5

7.6×10–7

6.12

100222876

2.876

4.26×10–5

1.3×10–6

5.90

100223382

3.382

5.01×10–5

1.8×10–6

5.76

100223879

3.879

5.74×10–5

2.3×10–6

5.64

100224279

4.279

6.33×10–5

2.8×10–6

5.55

100224930

4.93

7.30×10–5

3.8×10–6

5.42

100226239

6.239

9.23×10–5

6.1×10–6

5.21

100229080

9.08

1.34×10–4

1.3×10–5

4.87

100229858

9.858

1.46×10–4

1.6×10–5

4.80

100243524

3.524

5.22×10–5

1.9×10–6

5.72