Chem IA Bonding Lab

“The Effect of Electronegativity Difference on Conductivity” Jason Yuan 003934-080 January 4, 2012

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Design Aspect 1 Difference in Electronegativity by Compound Difference in Electronegativity ±0.05 1.8 1.9 0.5 2.3 2.2

Compound Sodium Iodide Potassium Iodide Magnesium Sulfate Sodium Chloride Lithium Chloride

Testable Question: How is the conductivity of a compound when dissolved in water affected by the compound’s difference in electronegativity? Hypothesis: If sodium chloride, which has the highest difference in electronegativity, is dissolved in water, it will have the highest conductivity. Independent Variable: Difference in electronegativity Dependent Variable: Conductivity (when dissolved in water) Controlled Variables:

Water pH Solution Concentration Volume of Solution

Design Aspect 2 Apparatus Used Beakers Sodium Iodide Potassium Iodide Magnesium Sulfate Sodium Chloride Lithium Chloride Electronic Weighing Scale Conductivity Probe Distilled Water Laptop with Logger Pro Stirring Plate The independent variable is being changed by altering the compound being dissolved, each of which has a different difference in electronegativity. The difference in electronegativity is being measured by subtracting the electronegativity of the cation from the electronegativity of the anion in the compound.

003934-080 The dependent variable is measured in microSiemens by a conductivity probe. The laptop and conductivity probe used was the same with each trial to avoid any possible errors in the data. Before and after each use, each beaker was washed with soap to prevent any external contamination from affecting the data.

Design Aspect 3 Compound

Mass of Compound (g) ±0.0005 g

Sodium Iodide Potassium Iodide Magnesium Sulfate Sodium Chloride Lithium Chloride

14.989 16.600 24.647 5.844 4.239

Solution Concentration ±0.05 mol 0.1 0.1 0.1 0.1 0.1

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The greatest difference in electronegativity tested was 2.3, and the lowest difference was 0.5.

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The conductivity will be measured in microSiemens.

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0.1 moles of each substance was weighed out by placing a weighing boat on an electronic scale and then setting tare to zero. Then the needed mass of each substance was weighed out.

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Each solution was made by dissolving 0.1 moles of a selected substance in 1 liter of distilled water. The solution was then stirred by being placed on a stirring plate for 5 minutes, after which it was taken off. This was done with all 5 compounds.

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Each trial was done by measuring out 200 mL of a selected solution into a beaker and then measuring the conductivity for a period of 180 seconds. The average conductivity of the period of time was then recorded. This was repeated 5 times with each solution.

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The program used for the data logging was Logger Pro.

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Data Aspect 1 The uncertainty of the conductivity was determined by halving the smallest unit of the number.

Trial # 1 2 3 4 5

Sodium Iodide Conductivity (µS/cm) ±0.5 µS/cm 4227 4226 4223 4218 4210

Trial # 1 2 3 4 5

Potassium Iodide Conductivity (µS/cm) ±0.5 µS/cm 4030 4026 4029 4035 4032

Trial # 1 2 3 4 5

Magnesium Sulfate Conductivity (µS/cm) ±0.5 µS/cm 3935 3957 3971 3972 3978

Trial # 1 2 3 4 5

Sodium Chloride Conductivity (µS/cm) ±0.5 µS/cm 3996 3993 3983 4014 4014

Trial # 1 2 3 4 5

Lithium Chloride Conductivity (µS/cm) ±0.5 µS/cm 4204 4208 4203 4211 4201

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Data Aspect 2 Compound Sodium Iodide Potassium Iodide Magnesium Sulfate Sodium Chloride Lithium Chloride

Average Conductivity Conductivity (µS/cm) ±0.5 µS/cm 4221 4030 3963 4000 4205

The average conductivity of each compound was determined by calculating the arithmetic mean of each set of trials, and then rounding to the nearest whole number. This was done to obtain a general picture of the conductivity of the compound when dissolved in water. In order of increasing conductivityMagnesium Sulfate: 3963 Sodium Chloride: 4000 Potassium Iodide: 4030 Lithium Chloride: 4205 Sodium Chloride: 4221

Compound Sodium Iodide Potassium Iodide Magnesium Sulfate Sodium Chloride Lithium Chloride

Standard Deviation of Data Standard Deviation (µS/cm) ±0.5 µS/cm 7 3 17 14 4

The standard deviation of each set of trials was determined by inserting the data into Microsoft Excel and using the standard deviation function programmed into Excel. Each standard deviation value was rounded to the nearest whole unit. The standard deviation was calculated to determine the variation in data of each set of trials, and thus see how closely grouped the data was.

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Data Aspect 3

Difference in Electronegativity 2.5 2 1.5 1 0.5 0 Sodium Iodide

Potassium Iodide

Magnesium Sulfate

Sodium Chloride

Lithium Chloride

Average Conductivity 4250 4200 4150 4100 4050 4000

Average Conductivity

3950 3900 3850 3800 Sodium Iodide

Potassium Magnesium Iodide Sulfate

Sodium Chloride

Lithium Chloride

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Conclusion and Evaluation Aspect 1 The hypothesis that sodium chloride would have the highest conductivity when dissolved in water was not supported by the data collected. It can be seen very clearly from the graphs that there is no direct correlation between difference in electronegativity and conductivity when dissolved in water. The compound with the highest conductivity was sodium iodide, which had the second lowest difference in electronegativity. The compound with the lowest conductivity was magnesium sulfate, which had the lowest electronegativity difference. It is clear that the data on the graph does not show any correlation between a compound’s difference in electronegativity and its conductivity when dissolved in water.

Conclusion and Evaluation Aspect 2 The range of values tested was not very large, and this limited the investigation. More values should have been tested, and more trials done of each value in order to improve on the data collected. Another issue was that the independent variable values were not changed at a constant amount. There were gaps in the differences in electronegativities, going from 0.5 to 1.8, and 1.9 to 2.2. Also, the solution used for each compound was from the same stock, which might have affected the trials. Because the beaker containing the stock solution was not covered, outside contamination might have affected later trials using that solution.

Conclusion and Evaluation Aspect 3 In the future, more values for electronegativity difference could be tested, such as the missing values between 0.5 and 1.8, since there is a large gap there. The data from those compounds with those differences in electronegativity might reveal a larger trend not seen due to the limited amount of data. Along with this, more trials could have been done with each compound to obtain more data, which could give a more specific image of the conductivity. To rectify the possible issue of contamination of the stock solutions, each solution could be covered when not in use. Another method of dealing with this issue is to make a new solution for every trial, but this would not be as effective, and much more time consuming.