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CHM 112
Section 1

Homework Assignment #27
Due April 19, 2006 by 8:05 a.m.

Practice (not to be turned in): 17.16, 17.52, 17.53, 17.54, 17.61, 17.62, 17.79, 17.84, 17.85

Choose the data set corresponding to the last digit of your Student ID Number.

The data given is the solubility in g/L for the indicated salt at each temperature. Use this data to find the Ho and So for the solubilization of the salt by using a van't Hoff plot. Find the slope and intercept graphically, using all of the data. Using the data from the Table of Thermodynamic Quantities, compare the calculated values for Ho and So to those found from your graph. Is the agreement good, bad, or indifferent?

Hints:

Write the reaction. This is critical for solving this problem correctly.

Note units of the solubility. You will need to find the equilibrium constant from the solubility, which we did not do in class. Recall that mass action expressions are expressed in terms of molarity and use the principals described earlier.

For finding the slope and intercept, use the techniques we learned earlier for Arrhenius plots of kinetic data.

To find Ho and So from data in the Table of Thermodynamic Quantities, follow the procedures in Homework 24 and Homework 25.

If you are assigned one of the mercury salts, note that Hg22+ is a single ion that contains two atoms. The mercury does not break apart into 2 Hg+ ions.

This is a long homework assignment and integrates ideas from several parts of the course, so will be worth 20 points.



Set:

T (oC)

0

MgF2
g/L

1

CaF2
g/L

2

SrF2
g/L

3

BaF2
g/L

4

PbCl2
g/L

5

PbBr2
g/L

6

PbI2
g/L

7

Hg2Cl2
g/L

8

Hg2Br2
g/L

9

Hg2I2
g/L

5
0.0167
0.0202
0.115
0.459
3.93
2.17
0.314
0.000134
2.86×10–6
3.48×10–8
15
0.0157
0.0215
0.128
0.477
4.35
2.70
0.450
0.000193
5.79×10–6
7.57×10–8
25
0.0155
0.0227
0.124
0.483
4.82
3.13
0.601
0.000317
9.81×10–6
1.53×10–7
35
0.0145
0.0241
0.131
0.511
5.44
3.63
0.812
0.000534
1.47×10–5
3.81×10–7
45
0.0143
0.0254
0.137
0.503
6.00
4.26
0.953
0.000806
3.63×10–5
6.58×10–7
55
0.0138
0.0264
0.133
0.527
6.43
4.76
1.27
0.00139
5.87×10–5
9.96×10–7
65
0.0136
0.0278
0.151
0.542
7.07
5.47
1.56
0.00180
6.65×10–5
1.89×10–6
75
0.0130
0.0287
0.141
0.556
7.67
5.72
1.94
0.00222
1.23×10–4
6.54×10–6
85
0.0127
0.0295
0.153
0.578
8.16
7.24
2.58
0.00425
1.89×10–4
8.48×10–6
95
0.0123
0.0305
0.151
0.576
8.80
7.77
3.28
0.00461
3.89×10–4
1.27×10–5


Turn in the following on a clean, full sheet of paper (not torn out of a notebook):

Name
Student ID Number
The answer to the question assigned. Show your work. Make the plot on a full sheet of graph paper, showing the best straight line used to determine the slope and intercept. Spreadsheets are not accepted.