Abstract:
In this experiment, an Iron (
Ⅲ
) oxalate coordination complex was synthesized and
analyzed to determine the empirical formula of K
w
[Fe
x
(C
2
O
4
)
y
] ∙z
H
2
O
. An oxidation-redox
titration was performed to determine the oxalate concentration and spectrophotometry was used
to find the concentration of iron within the unknown solution.
From part4A, at first, yellow
precipitation, then dark yellow precipitation, then brownish solid/solution, and then green crystal
were produced.”observations omit from abstract”
After leaving in the dark for few days, small,
oblong-shaped, emerald green, salt-like crystals, and 1.1918g of crystals were produced.
The empirical formula of the iron-oxalate compound turned out to be K
3
[Fe
Ⅲ
(C
2
O
4
)
3
] ∙3
H
2
O
,
where w=3, x=1, y=3, and z=3. This means that the ration of Fe: K: C
2
O
4:
H
2
O
is 1:3:3:3. (The
exact ratio between mmol of oxalate and mmol of iron was 3.06: 1.00, which gave the
approximation of a 3:1 ratio, and the exact ratio between mmol of water and iron was 3.21: 1.00,
which gave the approximation of 3:1 ratio). Through titration, the weight percentage of oxalate
was found to be 53.60 ± 1.50%, which could be converted into mmol per 100.0g of complex,
meaning that 608.9 ± 17.2mmol of oxalate were present. Through spectrophotometry, Beer’s
Law calibration equation was derived to be y = 10930x – 0.0102, which was then used to find the
concentration of Iron (
Ⅲ
) in the solution, and thus, the weight percentage of Iron (
Ⅲ
) – a value of
11.1 ± 1.4%. This can be converted to mmol of Iron (
Ⅲ
) in 100mL sample which value was
0.206 ± 0.028. This, too, could also be converted to mmol per 100.0g of complex, giving a value
of 199 ± 26mmol of iron preset. The initial mass of the Fe (NH
4
)(
SO
4
)
2
∙
H
2
O
compound was
1.2088g , which made 1.1918g of crystal product. Thus, determining that the complex is K
3
[Fe
Ⅲ
(C
2
O
4
)
3
] ∙3
H
2
O
, the percent of yield of the iron-oxalate complex was found to be 78.72%.