Lab 9

Topics: Electrolyte, Water, Electrochemistry Pages: 5 (915 words) Published: April 27, 2013
Laboratory 9

Lab title: Conductivity of solutions and Household Items

To understand the compounds that dissociate (break into ions) when dissolved in water. Determine ionic compounds are electrolytes. To identify solutions as electrolytic and non-electrolytic, and to identify variations in conductivity among electrolytes. Substances that are capable of conducting an electric current in solution are known as electrolytes. Substances that do not conduct an electric current in solution are known as non-electrolytes. Among electrolytes, the ability to conduct varies greatly. Some substances are excellent conductors, while others conduct only slightly. What could/should be observed:

If the compound conducts electricity the light-bulb would light up. If it was a very good conductor then it would be really bright (shown on table below by the ++1 strong electrolyte) if the compound was a good conductor or a poor conductor the bulb would faintly light up (shown on table below by the +1 weak). If it doesnt conduct then the light-bulb did not light up at all (shown on table below by the n× non-electrolyte) Materials:

Conductivity apparatus
Small disposable plastic cups
Safety Goggles
Distilled water
Purified "drinking" water
Cooking oil
Kitchen or bathroom surface cleaners
Listerine or Scope
Baking Soda (solution)
Tums (solution)
Dishwashing/laundry detergent
Tap water
Table salt
Sharpie® marker

1. Graduated cylinder to measure out approximately 100 mL of distilled water and place it in a very clean glass. In a separate clean glass, measure out 100 mL of tap water.

2. In a third clean glass, measure out 100 mL of purified drinking water.

3. Test all three types of water using the conductivity apparatus by carefully placing the exposed metal portions of the electrodes in the solutions to be tested.

4. Watch the relative strength of the LED light on your conductivity apparatus to determine which type of water (distilled vs. tap vs. purified) conducts electricity the best.

5. The LED light will blink repeatedly for solutions with high conductivity; it will be bright for solutions with moderate conductivity and dim for solutions with low conductivity.

6. Retain the distilled water to use as a "rinse" after testing the other solutions called for in this lab.

7. Measure out a new 100 mL sample of the distilled water. Add a "pinch" of salt to your sample of distilled water. Stir the salt-water solution until all of the salt dissolves.

8. Test the conductivity of the salt-water solution again. Note any changes. Rinse the electrodes with distilled water.

9. Add another "pinch" of salt to the salt water solution, stir, and test the conductivity again. Continue adding just a pinch of salt, stirring to dissolve, and testing the conductivity after each addition.

10. Now conduct the same test as in 3 and 4 above, except now you will be using a solution of sugar in distilled water. Start with a "fresh" sample of 100 mL distilled water. Add a pinch of sugar to the distilled water, stir, test, add another pinch, stir, test, etc

11. Rinse the apparatus between each test in the distilled water.

Comparing the conductivity of household solutions
1. Using the plastic cups provided in your kit, gather at least 10 different household products to test the conductivity of each.

2. Place each test solution in a separate plastic cup and make sure that the cups are labeled with the contents.

3. Test each of these solutions using your conductivity apparatus, rinsing the probes in distilled water thoroughly between each solution tested.

4. Rank the solutions in order of most to least conductive.

5. Using the solution that is the best electrolyte, make a dilution. To create a dilution, measure out 5 mL of the electrolyte solution and add 50 mL of distilled water....
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