Part 1 Synthesis of the silver colloid Procedure 3, 4 Pour 50 mL of 0.001 M stock solution of silver nitrate into a clean 250 mL beaker. Add a stirring rod. Heat the solution to a boil while stirring. Add DI water as necessary to maintain the 50 mL volume. Measure out 5 mL of 0.0388 M sodium citrate solution. Pour the sodium citrate solution into the beaker. Note the changes in the colloid appearance after the addition of sodium citrate solution. Boil for 10 minutes. (Again, add DI water as necessary to maintain the 55 mL volume.) Remove from heat and continue stirring for 15 minutes. How does the silver salt interact with the sodium citrate dihydrate? Draw a diagram on the molecular level of what is happening as the colloid forms in solution. Part 2 Analysis of the silver colloid 3, 4 Collect five clean dry glass vials. Add 5 mL of the silver solution to each of the five vials. Add 10 drops of 1M NaCl, 1 M HCl, 1 M NaOH, and 1 M glucose to each vial respectively with stirring. Clearly label the vials. Compare the appearance of the silver colloid in each of the vials. Record any changes in the colloid between the vials. Measure the pH of all five vials. How does the addition of an ionic substance change the pH of the colloid solution? How does the appearance of the colloid change as you add different types of solutions (acids, bases, salts, sugar)? Of the solutions that induced a change in the appearance of the colloid solution, what do they have in common? Dilute 2 mL of the original silver colloid solution with 10 mL of DI water. Using the HP spectrophotometer record a UV-Vis spectrum from (300 to 800 nm) of the colloid solution (remember to first take a blank spectrum with DI water.) Then add 0.100 mL (~4 drops) of electrolyte solution, you can choose either the acid, base or salt. Be sure to mix the solution in the cuvette after the addition of the electrolyte. Record a spectrum after the addition of the electrolyte at a time interval of 5 minutes. Compare the maximum wavelength of both spectra, and propose a theory for what is happening to the colloid in the solution. Remember to record the absorbance value for each lmax as well as any other changes you observe in both the solution and spectra. Scattering Analysis Take a sample of the original silver colloid and shine a white light flashlight onto the sample by placing the flashlight on the bottom of the vial with the light shining up to the ceiling through the colloid solution. Using a white piece of paper at a 90º angle from the sample, determine the color of the light scattered by the sample. How does the wavelength of this light correspond to the light being absorbed by or transmitted through the sample?