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LAB 1 - NaCl

Question: How does the amount of electrical current passing through a solution depend on the concentration of salt?





Test: _____________________________________________________________________________




          distilled water (dH2O)       NaCl (anhydrous)       triple beam balance
          beaker       glass rod electrophoresis chamber
          metal scoop       wax paper power supply
          P1000 micropipet/tips       graduated cylinder

Lab Instructions (Procedure):
  1. Make up your salt "stock" solution. Weigh out exactly 5.8 grams (gm) of NaCl and transfer them quantitatively to 100 mL distilled water (dH2O). Dissolve the salt and make sure the solution is thoroughly stirred.

  2. Add 300 mL dH2O to the electrophoresis chamber. Connect the power supply to the chamber and set the power supply to 100 volts (V), then check the current on the amp meter - it should read 0 milliAmps (mA). Record this value in your data table. Turn off the power supply.

  3. Add 1.0 mL of salt stock solution (5.8gm/100ml) to the electrophoresis chamber. Rock the chamber to mix the salt thoroughly. Read the current (mA) with the power supply set at 100V. (Try to get the earliest reading because the meter will slowly drift upward with time.) Record in data table.

  4. Continue adding 1.0 mL portions of stock solution to the chamber, each time recording the current with the power supply set at 100 volts until you have collected 5 to 6 readings.

  5. Dispose of salt solutions in the sink and rinse the chamber and stock solution beaker.

  6. Graph the data from your table.


            volume of        
            stock solution added       
    to the chamber
            relative concentration       
            of stock solution added       
    to the chamber
    0 0    
    1.0 5.8    
    2.0 11.6    
    3.0 17.4    
    4.0 23.2    
    5.0 29.0    

  7. Draw a graph showing how the electric current that goes through the solution depends on the concentration of the salt solution.

    Electric Current vs. Salt Concentration


  8. Analysis/Conclusion:
    1. Restate your hypothesis.
    2. State whether your hypothesis was right or wrong.
    3. Describe evidence from your data section that supports your conclusion.
    4. Using numbers, describe how the current changes as salt concentration is changed.

LAB 2     LAB 3     LAB 4     General Instructions

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