Dr. Roderick M. MacraeCHE 1513. Label two clean dry 100 mL beakers Trial A and Trial B. Into each weigh exactly an amount of NaOH between about 0.4 g and 1.3 g. Record the exact mass in the table below. Add 25.00 mL of distilled water to each beaker. When the NaOH has completely dissolved add 25.00 mL of the Cu2+(aq) solution, mixing gently as you do so. Record the exact volumes used in the table. Let the solutions stand (stirring occasionally) as you do part 4 below. 4. Prepare four different solutions from your stock solution having different known concentrations. Suggested volume ratios of Cu2+(aq) and H2O are: 10.00 mL: 10.00 mL; 10.00 mL: 20.00 mL; 10.00 mL: 30.00 mL; 10.00 mL: 40.00 mL. Record the actual exact volumes you used in the table overleaf, and calculate the concentration of each in moles/liter. Record these values in the table. Label the solutions Stock A through Stock D. 5. The next step is to filter the supernatants remaining after part 3 above. Set up two sets of filtration apparatus, and filter the Trial A and Trial B solutions. The objective is to obtain a clear (i.e. transparent, with no cloudiness) sample of pure supernatant suitable for spectroscopy. It may be necessary to filter more than once to obtain samples of this quality. As the concentration of supernatant is important, make sure all glassware is dry beforehand and do notwash the precipitate into the filter paper with distilled water. The filter paper and precipitate will not be needed for the remainder of the laboratory. Dispose of them appropriately. 6. Reread the instructions on the use of the spectrophotometer, set the measurement wavelength to 620 nm, and measure the color intensity (absorbance) at this wavelength on your sixsolutions (Trials A and B; Stock A through Stock D). Record all data in the table on the next page.
CHE151Lab12_CuSpectr.doc Dr. Roderick M. MacraeCHE 151Quantitative Data Stock Cu2+(aq) solution concentration: _________________ M Reaction solutions __________________________________________________________________________________ Solution Trial A Trial B __________________________________________________________________________________ Mass of NaOH _____________________ _____________________ mL H2O added _____________________ _____________________ mL stock Cu2+added _____________________ _____________________ Total mL solution _____________________ _____________________ Absorbance at 620 nm _____________________ _____________________ __________________________________________________________________________________ Standard (Diluted Stock) solutions __________________________________________________________________________________ Solution Stock A Stock B
You've reached the end of your free preview.
Want to read all 6 pages?
- Fall '15