Procedure for Determining Equilibrium Constant Lab Help me table 6 and 7 . Show

Question

Procedure for Determining Equilibrium Constant Lab

Help me table 6 and 7 . Show Work

PROCEDURE for DETERMINING EQUILIBRIUM CONSTANT (Kee) Fes (aq) SCN (aq) An Initial Set-Up l) Turn on computer before connecting spectrovis Plus. 2) After computer has completed the initial powering up, connect Spectrovis Plus with its USB cable to the computer B alibratin SpectroVisUnit Always check that the clear sides of the cuvette are optically clean before using--- DO NOT handle the cuvette on the clear sides of the cuvette-- 1) Click on the "Logger Pro" icon on computer desktop. Computer screen should show a large visible spectrum in the middle of the screen. 2) Click on "Experiment" at the top, then click on "Calibrate" and then "Spectrometer 1 3) Allow the computer to complete the wam-up period for the spectrometer 4) Fill a cuvette almost full with tap water. Dry and clean the clear sides of the cuvette. 5) Place the cuvette with water into the Spectrovis. (Be sure it is position correctly with the clear sides between the source and detector.) 6 Click on "Finish calibration" and when it has completed the calibration-blank scan click on "oK Preparing Calibration Standard Standard #4 will be prepared first, because it is needed when determining the wavelength for calibration (Part D. Standard #4 can then be the first standard used to prepare the calibration plot in Part E. It does not matter what order that the standards are used to prepare the plot. 1) Using the volumes and concentration for [Fe(NO) and [KSCN) in Table al, calculate new concentrations using the dilution formula (Mivr MFvF and record the new concentration values in Table #2 2) obtain a clean 50-mL, graduated cylinder 3) Fill 50-mL, graduated cylinder to 35-mL line with purified water 4) Using 5-mL plastic syringes, add 5.0 mL of 0.200M Fe(NO) and 4.0 mL of 0.0020M KSCN into the 50-ml. 5) graduated cylinder, pipette. Fill 50-mL graduated cylinder to 50 line using purified water and a plastic (Be sure bottom of water meniscus is on the 50-mL L graduated cylinder into a 50-mL plastic vial 7) Pour solution back into 50 graduated cylinder, and then back into 50 ml plastic vial Rinse 50-mL cylinder with purified water, and discard water 9) Repeat steps 3-8 for remaining standards in Table a value in Table if3 Place the IKSCN) value in Tabie #2 for the corresponding tFe(scN) rminin Wav for before using. Always check that clear sides of the cuvette are optically clean 1) Remove cuvette from Spectrovis and discard water out of cuvette. 2) Rinse cuvette with some of standard a4 and discard 3) Fill cuvette almost full standard i4 and place in Spectrovis on "Stop 4) Click on when the full spectrum is showing, click and then store latest so 5) Click on "Experimen

Explanation / Answer

The linear equation is given as y= 4144 x - 0.008933. This straight line plot was obtained by plotting concentration of Fe(SCN)2+ on x-axis and the corresponding absorbance on y-axis. In order to calculate the concentration of Fe(SCN)2+ for table 6, we just need to substitute the observed absorbance values (i.e y is given) and calculate the corresaponding concentrations (i.e. x needs to be calculated)

From the straight line equation, x = (y +0.008933)/4144. Thus [Fe(SCN)2+]= (Abs +0.008933)/4144.

The initial concentration of Fe3+ and SCN- can be obtained from table 5. The change in [Fe3+] and [SCN-] is equal to the amount of [Fe(SCN)2+] formed (As Fe(SCN)2+ gets formed, the concentration of Fe3+ and SCN- will decrease accordingly). Thus table 7 can be summarised as follows

Keq=

[Fe(SCN)2+]eq/[Fe3+]eq[SCN-]eq

Equilibrium constant can be calculated in each case by taking the ratio of equilibrium concentration of the product and reactants. ie. K = [Fe(SCN)2+]/ [Fe3+][SCN-]

Tube Absorbance [Fe(SCN)2+] 1 0.331 8.2 x 10-5 2 0.36 8.9 x 10-5 3 0.421 1.04 x 10-4

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