Gen Chem 2: Solubility Product Constant

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[Solubility Product Constant]|
Experiment 11|
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Molly McCabe|
4/18/2013|

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Data Tables:
Part 1 and Part 2 Experimental Data:
Standard| Calculated volume of copper sulfate in standards| Absorbance values| Blank| 0.0 mL| 0.0|
1| 1.25 mL| 0.094|
2| 3.75 mL| 0.065|
3| 2.50 mL| 0.099|
4| 3.50 mL| 0.129|
5| 5.00 mL| 0.187|

Collected Data| Test tube 1| Test tube 2| Test tube 3| Test tube 4| Test Tube 5| Initial volume (mL)| 0.05| 0.10| 0.0| 0.0| 0.0|
Final volume (mL) | 24.25| 22.10| 25.0| 23.70| 19.90| Total volume (mL) | 24.20| 22.0| 25.0| 23.70| 19.90|
Molarity S2O3-| 0.02519 M| 0.02519 M| 0.02519 M| 0.02519 M| 0.02519 M| [IO3-]| 0.0254 M| 0.0231 M| 0.0285 M| 0.0249 M| 0.0209 M| [Cu2+]| 1.66 x 10-2 M| 1.61 x 10-2 M| 1.76 x 10-2 M| 2.38 x 10-2 M| 3.58 x 10-2 M| Ksp| 1.07 x 10-5| 8.59 x 10-6| 1.43 x 10-5| 1.48 x 10-5| 7.48 x 10-4|

Class Data
Group| Trial 1 (Ksp)| Trial 2| Trial 3| Trial 4| Trial 5| Molly and Brooke| 1.07 x 10-5| 8.59 x 10-6| 1.43 x 10-5| 1.48 x 10-5| 7.48 x 10-4| Casey and Marissa| 4.60 x 10-6| 8.00 x 10-6| 9.24 x 10-6| 2.66 x 10-5| 1.59 x 10-5| Giang and Kristen| 1.11 x 10-5| 1.32 x 10-5| 1.56 x 10-5| 1.37 x 10-5| 1.81 x 10-5| Alicia and Dan| 6.01 x 10-6| 5.75 x 10-6| 1.92 x 10-6| 1.12 x 10-5| 1.48 x 10-5|

Calculated Data
Group| Average Ksp| Standard Deviation| Percent Error|
Molly and Brooke| 1.59 x 10-4| ± 3.29 x 10-4| -113471.4%| Casey and Marissa| 1.30 x 10-5| ± 8.80 x 10-6| -9185.7%| Giang and Kristen| 1.43 x 10-5| ± 2.64 x 10-6| -10114.3%| Alicia and Dan| 7.94 x 10-6| ± 5.06 x 10-6| -5571.4%|

Uncertainties:
10 mL volumetric flask| ± 0.02|
25 mL volumetric flask| ± 0.03|
1 mL volumetric pipet| ± 0.006|
5 mL volumetric pipet| ± 0.01|
4 mL volumetric pipet| ± 0.015|
3 mL volumetric pipet| ± 0.010|
50 mL graduated cylinder| ± 0.25|
Buret| ± 0.05|
Colorimeter| ± 0.0001|
Analytical balance| ± 0.0001|

Sample Calculations:
1. Standard solutions: M1V1 = M2V2
* Test tubes 1 and 2: 25 mL
* Test tubes 3-5: 10 mL
* M)(25 mL) = x(0.200 M), x = 1.25 mL

2. Total volume: final – initial = total
25 mL – 0.0 mL = 25 mL

3. [IO3-]: mol S2O31 LL of S2O31 mol I32 mol S2O31 mol IO33 mol I31 0.004 L = [IO3-]

0.02519 mol S2O31 L0.022 L S2O31 mol I32 mol S2O31 mol IO33 mol I31 0.004 L = 0.0254 M

4. [Cu2+]: * use y = mx + b equation from graph: Abs = m[Cu2+] + b * Plug in Abs. values: [Cu2+] = Abs. -bm
[Cu2+] = 0.094-0.013534.850 = 1.66 x 10-2 M
5. Ksp = [Cu2+][IO3-]
[1.66 x 10-2][0.0254] = 1.07 x 10-5

6. Average Ksp: (Ksp trial 1 + Ksp trial 2 + Ksp trial 3 + Ksp trial 4 + Ksp trial 5) / 5 = Avg. * 10-5 + 8.59 x 10-6 + 1.43 x 10-5 + 1.48 x 10-5 + 7.48 x 10-4) / 5 = 1.59 x 10-4

7. Standard Deviation: Xavg. -Xn2n-1
(1.59x10-4-1.07x10-5)2+(1.59x10-4-8.59x10-6)2+(1.59x10-4-1.43x10-5)2+(1.59x10-4-1.48x10-5)2+(1.59x10-4-7.48x10-4)2(4) 8. Percent Error: accepted-theoretical accepted x 100
1.4x10-7-(1.59x10-4)(1.4x10-7) x 100= -113471.4%
Discussion:
The objective of this experiment was to measure the solubility-product constant of a soluble salt. The solubility-product constant, represented as Ksp, states that for equilibrium to exist between a solid substance and its solution, the solution must be saturated and in contact with an un-dissolved solid. Ksp is therefore measuring the solubility of the solid that has relatively low solubility. The higher the solubility-product constant, the more soluble the solid present in solution. To measure the Ksp values, colorimetry and titration techniques were used.

The experiment was divided into two parts; part 1 involved using the colorimeter to find the concentration of the Cu2+ and part 2 used titration to find the concentration of IO3-. When both concentrations were found,...
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