A B C D E F 1 Part 2: Using the Nernst Equation to Determine lonic Concentration 2 IN 3 Conc. [Ag'] pAg 4 Dilution Calculation Experimental Theoretical Ecell Eget Voltages: 5 1 M Ag 0.393 6 0.8 M Ag 0.389 7 0.5 M Ag 0.383 8 0.3 M Ag 0.369 9 0.1 M Ag 0.351 10 Unknown 0.369 11 12 Graph of pAg vs. Ecell: Slope Experimental 13 Value of 14 Unknown Ag+ 15 Y-intercept molarity: 16 17 18 19 20 Student Data Part 1 Part 2 Type here to search Unknown # Part 2. Using The Nernst Equation to Determine lonic Concentration For Part 2 of this experiment, you will be provided 1.0 M silver nitrate solution, and you will use it to make diluted solutions of 0.8 M. 0.5 M. 0.3 M and 0.1 M concentrations, as described below, setting up the well plates as shown on the graphic on the previous page. In the parallel row of wells beneath these Ag" solutions, you will add 1.0 M Cul solution to each well. [Caution: silver nitrate will stain skin and nails big time. While at first hardly visible, the silver ion is reduced by light to metallic silver, the same basic principle as photography, but now your skin is the negative. At this point the dark brown silver stains are bound to your skin or nails and can not be scrubbed, or even bleached off effectively. Stained skin will slough off as new skin comes to the surface, in about a week. Stained nails will eventually grow out, but this can take months. Protect your hands with surgical gloves. Immediately wash for 5 minutes any portion of skin that contacts the silver nitrate solution to minimize staining.] To make 0.8 M Ag' solution: Add 3 drops DI water to 12 drops 1.0 M Ag" solution To make 0.5 M Ag' solution: Add 8 drops DI water to 8 drops 1.0 M Ag' solution To make 0.3 M Ag' solution: Add 7 drops DI water to 3 drops 1.0 M Ag' solution To make 0.1 M Ag' solution: Add 9 drops DI water to 1 drop 1.0 M Ag" solution On your report sheet calculate how these dilutions produce the respective molarities. You can use "drops" as volume. Freshly scour a copper strip and a silver strip to a shiny finish. Rinse off any threads of wool that might be stuck to the electrodes. Attach the electrodes to the voltmeter so that a positive voltage is seen when the copper electrode is dipped into the copper solution and the silver into the silver solution, then wait for the voltage to stabilize and record its value and molarity of the silver nitrate solution. Rinse the electrodes with distilled water, blot with a clean paper towel, then determine the voltage of another Ag' molarity. Repeat for all known concentrations and then test the unknown. Use a spreadsheet program to plot pAg vs. voltage. (Which should be the ordinate? Which should be the abscissa? See the discussion.) Use the trendline function to have the program plot the best straight line, then use it to determine the concentration of the unknown silver solution. On this same spreadsheet, in the column next to the experimental voltages, calculate the theoretical voltages that these concentrations should produce according to the Nernst equation. RELINDERS TO STUDENTS USEFUL INFORMATION somation