These are the procedures for the experiment and my data is plotted. Can you plea

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These are the procedures for the experiment and my data is plotted. Can you please help me with these questions when the absorbance of our solution is 0.541? The concentration we get using the equation is after dilution and I guess we have to do the calculation back to get the concentration before dilution to answer for Ksp. For comparison, Ksp = 3E-7

b. Part 3: Determination of the Ks and molar solubility of FeC204 Allow the contents to settle in the 125-mL Erlenmeyer flask with the yellow iron(lI) oxalate precipitate in it. c. Fold a piece of 11 cm filter paper and put it in a dry, long-stem Equipment thermometer 125-mL Erlenmeyer flask 11 cm filter paper dry, long-stem funnel 100-mL beaker 10-mL graduated pipet 100-mL volumetric flask funnel. Pour most of the liquid from the flask into the filter-paper cone (let the solid remain behind). Allow the funnel drain into a clean, dry 100-mL beaker. If any yellow particles come through with the filtrate, filter the solution again-the final solution should be absolutely clear d. Rinse your 10-mL graduated pipet with a little of the filtered solution, and then transfer 5.00 mL of the solution to a clean 100- mL volumetric flask. Materials 10% hydroxylamine hydrochloride 0.1 % 1,10-phenanthroline 10% sodium acetate e. Add the hydroxylamine hydrochloride, sodium acetate, and 1,10- phenanthroline in the same quantities as you did in preparing your standard iron solutions for analysis. Dilute to the mark with distilled water Safety For information on safety concerns see table in Part 2 Waste Disposal The solutions used in this experiment are environmentally harmless f. Prepare a blank in the same manner as before. Allow the solutions to stand for five minutes. Measure the absorbance of the solution containing the 5.00 mL of saturated iron(I) oxalate g. and can be disposed of by flushing down the drain with water h. Read the concentration of iron in the solution from your calibration curve Experimental Procedure Individual work: Do this part of the experiment on your own a. Equilibrium constants vary with temperature. Measure the temperature of the solution in equilibrium with the solid iron(II) oxalate. This is the solution you prepared one or two weeks earlier

Explanation / Answer

1) From steps (d) and (e) it is clear that the iron oxalate sample obtained originally was diluted from 5ml to 100ml.So the dilution factor is (5/100) for the sample.

The absorbance=0.541 is for the diluted sample so you get the concentration for the diluted sample from the callibration curve of the standard solutions.

Using Beer's law ,

Absorbance=e*l*C

where e=absorptivity of species(Fe2+)

l=path length of light(1 cm)

A callibration curve between Abs and concentration is linear of the form y=mx+c,

y=Abs ,x=concentration ,m=slope=el

equation for the callibration curve:

Abs=8.8*10^-3*x +0.0601

where x=concentration of the diluted sample

So,x=(Abs-0.0601)/(8.8*10^-3)=(0.541-0.0601)/(8.8*10^-3)=54.648 uM

For the concentrated sample, C*dilution factor=54.648 uM

or C*(5/100)=54.648 uM

C=1092.954 uM=1092.954 *10^-6 M=0.0109M

2) FeC2O4(s) <---->Fe2+(aq) +C2O42-(aq)

ksp (FeC2O4)=[Fe2+][C2O42-]

[fe2+]eq=(0.0109)M

[C2O42-]eq=(0.0109)M   ,eq=equilibrium concentration

ksp (FeC2O4)=[Fe2+][C2O42-]=(0.0109)((0.0109)=1.188*10^-4

pKsp=-log Ksp=-log (1.188*10^-4)=3.9

literature value=2.1*10^-7M

pKsp=-log (2.1*10^-7M)=6.7

% error=[|(experimental value-literature vaue)|/literature value]*100=[(6.7-3.9)/6.7]*100=41.8%

4) Solubility in g/L=molarity*molar mass=(0.0109mol/L)*(143.91g/mol)=1.569g/L

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