Colorimetric determination of Iron Flashcards
(39 cards)
what is one method for the determination of iron
based on the formation of the orange-red Iron(II)-orthophenanthroline complex
what is Iron(II)-orthophenanthroline often abbreviated to
“ferroin” with the molecule formula:
is orthophenanthroline an acid or base
base
what happens when orthophenanthroline is added to an acidic solution and WHY
it becomes pronated and giving up the phH+ ion because it is a BASE
what is the best pH for the formation of the Iron(II)-orthophenanthroline complex
3.5
why is a pH of 3.5 the best for the formation of the complex
because at this pH it is the best to PREVENT the formation of various iron salts (phosphates)
what is the importance of the hydroxylamine hydrochloride in this experiment
it is a reducing agent that prevents the iron (II) from being oxidized to iron (III) during the experiment
what is a benefit once the Iron(II)-orthophenanthroline complex forms
it holds it colour for a long period of time which allows for the determination of the concentration of the Iron(II)-orthophenanthroline complex
describe how colour is seen in the visible wavelength section of the electromagnetic spectrum
it “removes” them from the spectrum and the solution will appear to be a mixture of the colours NOT absorbed
what colours does the Iron(II)-orthophenanthroline complex absorb
green and blue light
what colour does the Iron(II)-orthophenanthroline complex appear
red-orange
what was the specific wavelength the Iron(II)-orthophenanthroline complex was measured at
508 nm (a shade of GREEN)
what is transmittance (T)
the relationship between the power of the original beam (Po) of light and the emerging beam of light/the remaining power after the beam has passed through the sample (P)
is the relationship between transmittance and solution concentration direct or indirect
not direct
is the relationship between absorbance and solution concentration direct or indirect
direct
what is the equation for Beer’s Law
A=abc
what do the different variables in Beer’s law indicate
A=abc
A is absorbance
a is absorptivity constant
b is cell width
c is the concentration
what is the fundamental law governing the absorption of all types of electromagnetic radiation
A=abc
(Beer’s law)
does Beer’s law only apply to solutions
NO - applies to solids and gases as well
why is a blank used in spectrophotomerty
to correct for a loss in beam power at each interface due to reflection and scattering by larger molecules
was it okay to use tap water, yes or no>
NO - tap water contains dissolved iron and other ions which messes with the results
how much of the iron salt solution was put into a 50 mL beaker
about 40 mL
what does iron salt refer to
Iron (II) ammonium sulfate hexahydrate
how were the 5 different solutions and blank created in this experiment
blank
- 0mL of iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
solution 1
- 1 mL iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
solution 2
- 2 mL iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
solution 3
- 3 mL iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
solution 4
- 5 mL iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
solution 5
- 10 mL iron salt
- 2.0 mL 10% hydroxylamine hydrochloride
- 3mL Orthophenanthroline
