I did a lab on Spectrophometric Determination of Iron in Vitamin Tablets, and I

Question

I did a lab on Spectrophometric Determination of Iron in Vitamin Tablets, and I put 5.00 mL of a 0.352 g/L Fe(II) stock solution into a 50.00 mL volumetric flask. I added 15 drops sodium citrate to make the pH between 3 and 4. I then added 1.0 mL hydroquinone and 1.5 mL o-phenanthroline solution, then I diluted with water to the 50.00 mL mark. I then analyzed the solution in the UV-vis spectrometer and I came up with an absorbancy of 1.0409. My Reagent blank had an absorbancy value of 0.0199. How would I calculate the concentration (in M) of Fe?

Explanation / Answer

we can simply calculate the concentration of unknown as the following formula

                       Aunk/Ast = cunk/cst,

                       Aunk   = absorbance of unknown

                      Ast         = absorbance of standard solution

                                  cunk        = concentration of unknown

                                     cst         = concentration of standard

                 mole of the substance = gram of the substance x 1 mol / molar mass of the substance

                         concentrationof Fe2+ in standard                    = 0.352g/Lx mol / 56 g =0.00629 mole/L

in this problem you measured absorbance in standard solution only right .

when you known the absorbance in unknown tablet solution then you have to apply values in the above formula . will give the unknown concentration of Fe in iron tablet.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.