Potassium tris(oxalato) ferrate (III), also known as potassium ferrioxalate, is a green crystalline- compound of octahedral geometry. It is a metal complex of iron with three oxalate (C2O42-) ligands bonded to the central metal atom (Fe). These ligands are bidentate, meaning that each of them binds to the metal atom at 2 different places.
Potassium ferrioxalate is a very interesting photosensitive material. In solution, it reacts with
2− light photons and undergoes a reduction reaction and decomposes to give Fe(C2O4)2 .
Experimental Procedure
I. Preparation of Potassium tris(oxalato) ferrate(III) trihydrate K3[Fe(C2O4)3].3H2O
a. In a beaker place 5 g of ferrous ammonium sulfate in 20 mL of warm water containing 1 mL of dilute sulfuric acid.
b. Stir the solution well.
c. Add to the beaker a solution of 2.5 g of oxalic acid dihydrate in 25 mL of water.
d. Slowly heat the mixture to boiling (beware of bumping) then allow the yellow precipitate to settle.
e. Decant the supernatant using a Buchner funnel making sure it has a properly fitted filter paper.
f. Add 15 mL of hot water to any solid remaining in the beaker, stir and filter.
g. Drain well and then transfer all the precipitate from the filter paper back into the beaker with 10 mL
hot water.
h. Add to the beaker 3.5 g solid potassium oxalate monohydrate and heat to approximately 40°C.
i. Add slowly, using a dropper, 9 mL of "20 vol" hydrogen peroxide.
j. If the precipitate looks yellowish, not brown and settles readily, decant the supernatant, add a
solution of 0.2 - 0.4 g potassium oxalate monohydrate in 1 - 2 mL water and then hydrogen peroxide
dropwise until the precipitate dissolves. Then add the previously decanted supernatant.
k. Heat to boiling, and add a solution of 2 g of oxalic acid dihydrate in 30 mL of water in portions, add 20 mL initially, then if the brown precipitate still remains, add more solution little by little until it all dissolves.
l. Boil the clear solution down to a volume of 40 to 50 mL.
m. Add 95% ethanol slowly until a precipitate starts to form (~ 30 mL).
n. Cool and leave to crystallize.
o. Filter and wash the crystals on the Buchner funnel with a 1:1 ethanol/water mixture and finally with
acetone.
p. Dry in the air and weigh.
The complex is photosensitive and should not be exposed to light unnecessarily. Store in a sample bottle wrapped in foil. The bright green crystals on exposure soon become covered with a yellow powder of ferrous oxalate.
2K3[Fe(C2O4)3].3H2O 2FeC2O4.2H2O + 2CO2 + 3K2C2O4 + 2H2O
II. Determination of the oxalate content of Potassium trisoxalatoferrate(III) trihydrate.
The iron(III) complex is first decomposed in hot acid solution and the free oxalic acid is titrated against standard (0.02 M) potassium permanganate solution. No indicator is required.
a. Weigh accurately about 0.2 g of the potassium trisoxalatoferrate(III) complex previously prepared.
b. Boil the sample with 50 mL of 1 M sulfuric acid in a conical flask.
c. Allow the solution to cool to about 60°C.
d. Titrate slowly with a standard potassium permanganate solution.
e. Continue titrating until the warm solution retains a slight pink color after standing for about 30 sec.
III. Photochemical reactions of Potassium trisoxalatoferrate(III) trihydrate.
a. Prepare a solution containing 0.2 g of your sample in 15 mL of dilute sulfuric acid.
b. Dilute the solution to 50 mL with distilled water and expose it to sunlight for one hour (note
carefully what happens).
c. Titrate with the standardized potassium permanganate solution to determine the amount of
reducing agent present.
Postlab Assignment
I. Preparation of Potassium tris(oxalato) ferrate(III) trihydrate K3[Fe(C2O4)3]
II. Determination of the oxalate content of Potassium trisoxalatoferrate(III) trihydrate.
2. Calculate the percentage by weight of oxalate in the complex; compare this with the theoretical
value and then calculate the percentage purity of the complex.
In: Chemistry
A student loaded a mixture onto a small flash chromatography
column in 1 mL of ethyl
acetate, then proceeded to elute with hexanes/ethyl acetate 10:1.
He/she found that all of the mixture came off in the first 3
fractions, with no separation. What technical mistake did the
student make?
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A compound has a pKa of 7.4. To 100mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0M hydrochloric acid. What is the resulting pH?
In: Chemistry
7.1 g of water ice at 268.4 K is mixed with 234 g of liquid
water at 304.7 K in an insulated container under an external
pressure of 1.00 bar. Answer the following questions assuming that
the physical properties of water and ice are constant over the
range of interest. Physical properties for water and ice are given
below:
Cp,m,ice = 1.95 J g-1 K-1
ΔHfusion,ice = 333.4 J g-1
Cp,m,water = 4.18 J g-1 K-1
Melting point of ice: 273.15 K
1) What will be the final form of the system? Select one that
applies
(a)
Water
(b)
Mixed water and ice
(c)
Ice
2)What is the final temperature, Tf (in K), of the system when it
reaches equilibrium?
Tf = ____________ K.
In: Chemistry
why is it unlikely for magnesium to form a cation with a charge of 1+?
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1)Potassium hydrogen phthalate is a solid,
monoprotic acid frequently used in the laboratory to standardize
strong base solutions. It has the unwieldy formula of
KHC8H4O4. This is
often written in shorthand notation as KHP.
How many grams of KHP are needed to exactly neutralize
21.1 mL of a 0.399 M
potassium hydroxide solution ?
grams KHC8H4O4.
2) Potassium hydrogen phthalate is a solid,
monoprotic acid frequently used in the laboratory to standardize
strong base solutions. It has the unwieldy formula of
KHC8H4O4. This is
often written in shorthand notation as KHP.
What volume of a 0.363 M barium
hydroxide solution is needed to exactly neutralize
4.46 grams of KHP ?
ANSWER: mL barium
hydroxide
In: Chemistry
Below is a list of pairs of compounds. Choose the pairs from the list that would NOT form a precipitate if mixed together.
a. KCl and Na3PO4
b. Ca(NO3)2 and MgSO4
c. FeCl3 and LiOH
d. CuSO4 and (NH4)3PO4
e. sodium nitrate and calcium chloride
f. sodium sulfate and barium nitrate
g. zinc nitrate and potassium sulfate
h. lead(II) nitrate and sodium carbonate
i. potassium phosphate and cobalt(II) chloride
j. copper(I) nitrate and magnesium chloride
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1a) A block of an alloy of mass 33.0 g and at a temperature of 289.36 K is placed in a calorimeter containing 36.0 g of ethylene glycol at 348.15 K. If the final temperature of the alloy and ethylene glycol is 306.28 K, calculate the specific heat (in J/g/K) of the metal. The specific heat of ethylene glycol is 2.39 J/g/K. Express your answer to three significant figures in scientific notation.
b) A 0.0763 g sample of solid RbBr (s) is dissolved in 449 mL of water in a coffee cup calorimeter. Once all of the RbBr (s) is dissolved in the water, the final temperature of the solution is found to be 21.76°C. If the initial temperature of the water in the calorimeter was 24.26 °C, calculate the calorimeter constant (in J/K) for the coffee cup calorimeter.
Report your answer to three significant figures.
The heat of the solvation of RbBr (s) is 21.88 kJ/mol.
c) For a given chemical process, the system absorbs 338 kJ of heat and the surroundings perform 348 kJ of work on the system. What is the value of ΔU (in kJ) for the process? Report your answer to three significant figures.
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Consider the reaction, N2(g) + 3 H2(g) → 2 NH3(g). Suppose 56 g of N2(g) reacts with 18 g of H2(g).
d. What is the limiting reactant?
e. When the reaction is complete, how many grams of NH3(g) are produced?
f. When the reaction is complete, how many grams of N2(g) remain?
g. When the reaction is complete, how many grams of H2(g) remain?
h. If the reaction actually produced 55 g of NH3(g), what is the percent yield?
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For the reaction Ti(s)+2F2(g)→TiF4(s) compute the theoretical yield of the product (in grams) for each of the following initial amounts of reactants. a)6.0 g Ti, 6.0 g F2 (express answer to two sig figs) b)2.3 g Ti, 1.4 g F2 (express answer to two sig figs) c)0.234 g Ti, 0.298 g F2 (express mass to three sig figs) Please show steps!
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Which statements regarding combustion analysis to determine
percent composition are not correct?
I. The mass of oxygen in the sample
compound can be determined from the mass of carbon dioxide that is
produced.
II. If a compound contains an
element other than carbon and hydrogen, combustion analysis cannot
be used to determine its empirical formula.
III. Combustion analysis data alone
is not sufficient to determine the molecular formula with
certainty.
IV. If some CO is produced rather than all CO2, then the
empirical formula that is calculated will be too high in
carbon.
| a. |
I, II, and IV are not correct. |
|
| b. |
II and III are not correct. |
|
| c. |
I, II, and III are not correct. |
|
| d. |
I and II are not correct. |
|
| e. |
II, III, and IV are not correct. |
In: Chemistry
For this assignment, the target compound that you should
synthesize is benzyl methyl ether. This is a
substitution reaction. Examine the product and determine which
bonds may be formed. Keep in mind the
substitution pattern of the product and the nature of the mechanism
accommodated by this arrangement.
starting materials: benzyl chloride, ether, NaOMe
A. Approx TLC values of product and starting material
B. Write mechanism for this reaction
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Calculate ?G?rxn and K for each of the following reactions.
Part A
The reaction of Cr2+(aq) with
Cr2O2?7(aq) in acid solution to form
Cr3+(aq).
Calculate ?G?rxn.
Part B
Calculate K.
Express your answer using two significant figures.
Part C
The reaction of Cr3+(aq) and Cr(s) to form
Cr2+(aq). [The reduction potential of
Cr2+(aq) to Cr(s) is -0.91 V.]
Calculate ?G?rxn.
Express your answer using two significant figures.
Part D
Calculate K.
Express your answer using one significant figure.
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Carbon dioxide makes up approximately 0.04% of Earth's atmosphere. If you collect a 2.5 L sample from the atmosphere at sea level (1.00 atm) on a warm day (27 ∘C), how many CO2 molecules are in your sample?
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