Chem Lab Procedure

Topics: Chemical equilibrium, Laboratory glassware, Water Pages: 2 (388 words) Published: May 12, 2013
1.) Preparation of stock solution.
a. Using volumetric pipets, prepare a stock solution. Pipet 5mL of 0.200 M Fe(NO3)3 in 1M HNO3, 1.00mL of 0.002 M KSCN and 4.00mL distilled H2O into a large test tube and mix thoroughly. Because the moles of Fe(+3) used is much greater than the moles of SCN-, we can assume the reaction goes to stoichiometric completion. 2.) Preparation of solution for the standard curve.

b. Using your stock solution and volumetric pipets, prepare the following standard solution: i. 5mL stock solution + 5mL distilled water
ii. 3mL stock solution + 7mL distilled water
iii. 1mL stock solution + 9mL distilled water
c. Determine the concentration of FeSCN(+2) in each solution d. Using the spectrometer, measure absorbance of each solution at 447nm. Use the same small test tube for all measurements. Start with the least concentrated solution. Rinse the test tube with a small amount of solution, discard, and then fill with the solutions. Repeat with the two other standard solutions. e. Construct a graph of Absorbance vs. Concentration.

3.) Obtain 2clean dry 100mL beakers. From solution cart, 35mL 0.002M Fe(NO3)3 in 1 M HNO3 in one beaker and 20mL 0.002 M KSCN in the other. 4.) Prepare the following solutions in the large test tubes using volumetric pipets. 5.) Thoroughly mix each solution to ensure equilibrium.

6.) Determine initial concentration of Fe(+3) and SCN(-) in each solution and record the values on the Data Sheet. 7.) Transfer each solution, one at a time, to the small test tube used to measure the absorbance. Fill the test tube about ¾ full. Measure and record absorbance for each solution. 8.) Use the standard curve to determine the equilibrium concentration of FeSCN(+2) in each. 9.) Use stoichiometry to determine he equilibrium concentration of Fe(+3) and SCN(-) in each solution. 10.) Calculate the equilibrium constant for each solution and...
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