Question

Calculate initial concentration of Fe+3 for tubes 1-3. Show your work.

Procedure A. Determination of B for Beer's Law 1. Using a buret, add 4.00 mL of 0.0025 M Fe(NO3)s (which is in 0.1 M HNOs) to a 100- mL volumetric flask. Add enough deionized water to bring the total volume to the mark on the neck of the flask. Stopper and shake the flask. Label this flask “Diluted Fe.” spectrophotometer tubes (cuvettes), they are too small to use at this point. 0.1 M HNOs. You will use a 5.00 mL volumetric pipet to measure the 1.0 M KSCN. 2. Obtain three 16 x 150 mm test tubes and number them 1-3. DO NOT use the 3. Properly prepare two burets, and fill them with the solutions required: diluted Fe3 and Your instructor will show you the correct use of the pipet. 4. Into each test tube, place the specified amount of each solution as listed on Table 1. TABLE 1 TEST TUBE DILUTED Fe3 1.00 2.00 3.00 mL of 1 M KSCN 5.00 5.00 5.00 mL of 0.1 M HNO3 4.00 3.00 2.00 2 5. Once all the contents of a test tube have been added, use a vortex mixer to mix 6. Following the instructions on the sheet next to the Spectronic 20, prepare a blank and use 7. Pour the reaction mixture for test tube I into a spectrophotometer tube (cuvette) so that it 8. Place the cuvette into the spectrophotometer, the light source of which is already pre-set thoroughly. it to adjust the 100% transmittance. is two-thirds full. Wipe the outside of the cuvette with a Kimwipe. to 450 nm. (Do not adjust the wavelength setting! If you have questions, see your instructor.) Record the percent transmittance (%T) for the sample to the nearest 0.1%.

Answer 1

Concentration of Fe(Na_3)_3 to begin with = 0.0025 M dilution: we have N_1V_1 = N_2V_2 A ml 0.0025m Fe(N0_3)_3 is diluted to 100 ml 4 times 0.0025 = 100 times N_2 N_2 = 10_4 M 10^- 4 m diluted Fe(N0_3)_3 is further diluted Test tube 1 1ml 10^- 4 M diluted to 10 ml total volume 1 times 10 6 - 4 = N2 times 10 N_2 = 10^- 5 M Fe(N0_3)_3 Test tube 2 2ml 10^- 4 M diluted to 10 M_l total volume 2 times 10 - 4 = 10 times N_2 N_2 = 2 times 10^- 5 M Fe(N0_3)_3 3 M_l 10^- 4 M diluted to 10 ml total volume 3 times 10^- 4 = 10 times n_2 N_2 = 3 times 10^- 5 M Fe(N0_3)_3