Experiment M03
Preparation of an iron complex
Name:
Seat No.:
Date:
Grade:
Calculation:
1. Calculate the theoretical yield, i.e. the mass of potassium trioxalatoferrate(III) expected from
complete conversion of the mass of iron(II) ammonium sulphate used.
FeSO4(NH4)2SO46H2O  K3Fe(C2O4)3 3H2O
391.8
490.8
7 .5
Theoretical yield =
x 490.8 = 9.395 (g)
391.8
2.
Calculate the percentage yield in this exercise, i.e. the percentage of the theoretical yield that
has actually been achieved.
mass of product
% yield =
x 100%
9.395
=
%
Questions for discussion:
1.
What is the name of the compound precipitated in procedure a?
Write an equation for the reaction.
Hydrated Iron (II) oxalate
Fe2+(aq) + C2O42-(aq) + 2H2O(l)  FeC2O4 2H2O(s)
2.
In procedure d, why should the temperature be kept at about 40 oC?
Both H2O2 and Fe(OH)3 are unstable to heat.
3.
Write an equation for the reaction.
Colourless gas (O2) is evolved; brown ppt [Fe(OH)3] is observed.
FeC2O4 + 6K2C2O4 + 3H2O2  4K3Fe(C2O4)3 + 2Fe(OH)3
4.
Why excess oxalic acid should be avoided in procedure f?
Write an equation for the reaction.
The crystals would be contaminated with oxalic acid.
2Fe(OH)3 + 3H2C2O4 + 3K2C2O4  2K3Fe(C2O4)3 3H2O + 3H2O
5.
In procedure g, what is the action of the ethanol?
Why is it effective?
The crystals are soluble in water, but very sparingly soluble in ethanol.
(Decrease the solubility of the product)
6.
In procedure h, why is it necessary to exclude light?
Why are the crystals finally washed with ethanol?
Because the crystals are photosensitive.
To facilitate drying.
P.3