Lab 2
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Department of Chemistry Inorganic Chemistry Laboratory
Name : Yiu Sze Chun Student No : 100155233 100155233 Section : _01_ Date : 09-03-2012
Long Report Data Sheet
Title : Experiment 2: Spectra of Cr(III) Complexes Objective : . Part A (Synthesis of Tris(ethylened Tri s(ethylenediamine)chromium(III) iamine)chromium(III) Chloride; [Cr(en)3]Cl3 3H2O) 1. To Synthesize Tris(ethylenediamine)chromium(III) Tris(ethylenediamine)chromium(III) Chloride by Heating Chromium(III) C hromium(III) Chloride Hexahydrate with Ethylenediamine followed by precipitation pr ecipitation in concentrated HCl-Ethanol Mixture 2. To Determine the Percentage Yield Yield of product by weighing weighing the product 3. To Calculate Molar Absorptivity and long Wavelength W avelength of the Complex with Analyzing the UV Spectra Part B (Synthesis of Tris(2,4-pentane Tris( 2,4-pentanedionato)chromium(III); dionato)chromium(III); Cr(C5H7O2)3) 1. To Synthesize Tris(2,4-pentanedionato)chromium(III) Tris(2,4-pentanedionato)chromium(III) by Heating with Acetylacetone Acet ylacetone and Urea in deionized water 2. To Determine the Percentage Yield Yield of product by weighing weighing the product 3. To Calculate Molar Absorptivity and long Wavelength W avelength of the Complex with Analyzing the UV Spectra .
Part C (Trichlorochromium(III) Hexahydrate; CrCl3 6H2O) 1. To Calculate Molar Absorptivity and long Wavelength W avelength of the Complex with Analyzing the UV Spectra given -
2. To Arrange the Spectrochemical series of three ligands li gands of the above complexes, en, C 5H7O2 and Cl
-
Procedure and Observation : Part A. . Synthesis of Tris(ethylenediamine)chromium(III) Chloride; [Cr(en)3]Cl3 3H2O
1
Procedures . In a 100 ml Beaker, 1.685 g CrCl 3 6H2O was mixed with 0.2 g Decolorizing Charcoal.
2
In fumehood, 2.60 ml of Ethylenediamine was added to the mixture powder and then stirred well.
3
The mixture was heated to dryness.
4
6.5 mL of ethanol on cooling was added to the mixture, and then be filtered off by Suction Filtration in Buchner Funnel.
5
Few portions of Ethanol was added to the slurry so as to remove excess Ethylenediamine. On the other hand, the residue was air-dried. During drying, 6.5 ml 1.7M Hydrochloric Acid was heated in a hot water bath about 60 . In addition, 10 ml of Ethanol was mixed with another 6.5 ml Hydrochloric Acid in a 150 ml Beaker with ice bath. After drying of the dark slurry, the solid was transferred into a beaker. Then, the 6.5 ml warm Hydrochloric Acid was added into it and swirled the mixture for one minute with warm bath. The solution was rapidly filtered with a clean Buchner Funnel. Then, the filtrate was rapidly added to the Hydrochloric Acid-Ethanol Mixture with ice bath.
6
7
8
9
The solution mixture was washed with ethanol and air-dried. 10 The yield of the product was recorded.
Observation Chromium(III) Chloride Hexahydrate was green solid powder, while the decolorizing Charcoal was black powder. Ethylenediamine solution was in coloress liquid. After addition, the resulting solution became black with heat given off. White smoke was also observed. Fume and bubbles were evolved during heating. The black solution turned to viscous dark grey (with little purple) slurry when it came to dryness. Ethanol was colorless. After addition, dark grey slurry solution was formed. After filtration, some sticky dark greenishyellow slurry was obtained with pale brown filtrate. Some purple spot on filter paper was removed.
Hydrochloric Acid was colorless solution. For the heating one, there were some bubbles given off, whereas there is no observable change in mixture. During the addition of Hydrochloric Acid, some smoke was given off and black solution was obtained.
The black solid was obtained, while the filtrate was in brown liquid. During the cooling in ice bath, some solid was appeared in the bottom of beaker and more and more was formed time by time. Fiber-liked Yellowish-orange solid was obtained. 0.186 g of product was collected.
Part B. Synthesis of Tris(2,4-pentanedionato)chromium(III); Cr(C5H7O2)3
1
2
3
Procedures 0.535 g of CrCl3 6H2O was added in a 100 ml Beaker. Then, 10 ml D.I. Water was added into the beaker. After complete dissolution, 3.820 g of Urea and 1.20 ml of Acetylacetone were added to the mixture. The reaction mixture was heated for an hour and be covered by a watch glass. .
Observation Chromium(III) Chloride Hexahydrate was green solid powder. After addition of Water, a green solution was formed. Urea was a shiny white solid, while Acetylacetone was colorless liquid. After mixing, a dark green solution was formed. Fume was given off with many bubbles. The vapor of the mixture was condensed on the watch glass. The solution became purple slurry.
4 5
After 1 hour, the reaction mixture was filtered off with Buchner Funnel. The yield of the product was recorded.
Data : Part A
Weight of Chromium(III) Chloride: 1.685 g Volume of Ethylenediamine: 2.60 ml Weight of Product: 0.186 g Description of Product: Yellow Powder Part B Weight of Chromium(III) Chloride: 0.535 g Weight of Urea: 3.820 g Volume of Acetylacetone: 1.20 ml Weight of Product: 0.541g Description of Product: Shiny Purple Powder
The residue was shiny purple powder with some dark powder. 0.541 g of product was collected.
Data treatment : 1. To Calculate the percentage yield of the product formed Part A
CrCl3•6H2O + 3H2NCH2CH2NH2 Cr(en)3Cl3•3H2O + 3H2O For Limiting Reagent: There are two staring materials and according to the balanced equation,
no. of mole of Chromium(III) Chloride Hexahydrate =
no. of mole of Ethylenediamine =
= 3.8912 x10
-3
-2
= 6.3234 x10 mole
mole
From the equation above, the mole ratio of Chromium(III) Chloride Hexahydrate and Ethylenediamine is 1:3.
no. of mole of Ethylenediamine =
-2
= 1.2971 x10 mole
As Chromium(III) Chloride Hexahydrate contains the least number of mole, so it is Limiting Reagent. For Product: From the equation above, the mole ratio of Chromium(III) Chloride Hexahydrate and product is
1:1.
no. of mole of product =
= 4.7362x10
Percentage yield of product =
-4
mole
× 100% =7.49%
Part B 3+
Cr
+ CH3COCH2COCH3
+
Cr(C5H7O2)3 + 3H
For Limiting Reagent: There are two staring materials and according to the balanced equation,
no. of mole of Chromium(III) Chloride Hexahydrate =
-3
= 2.0077 x10 mole
no. of mole of Acetylacetone =
= 0.01147 mole
From the equation above, the mole ratio of Chromium(III) Chloride Hexahydrate and Acetylacetone is 1:1. As Chromium(III) Chloride Hexahydrate contains the least number of mole, so it is Limiting Reagent. For Product: From the equation above, the mole ratio of Chromium(III) Chloride Hexahydrate and product is
1:1.
no. of mole of product =
= 1.5487x10
Percentage yield of product =
-3
mole
× 100% =77.14%
2. To Find the Position the long Wavelength (nm) Absorption Peak (10 Dq) for each -1 compound, and Convert the Wavelength unit into Wavenumbers (cm ). Calculate the Molar Absorptivity, ,for each compound at its absorbance maximum.
The equation of finding the Molar Absorptivity was given as below
=
log I o / I CI
Where I = 1cm C = Molar Concentration of the Complex For Cr(en)3Cl3•3H2O
The Maximum Absorption Peak = 466 nm
Wavelength =
-1
= 21459.2275 cm
Molar Absorptivity =
-1
-1
= 25.6 M cm
For Cr(C5H7O2)3
The Maximum Absorption Peak = 570 nm
Wavelength =
-1
= 17543.8597 cm
Molar Absorptivity =
-1
-1
= 102.86 M cm
For CrCl3•6H2O
The Maximum Absorption Peak = 632 nm
Wavelength =
-1
= 15822.7848 cm
Molar Absorptivity =
-1
-1
= 24.4 M cm
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3. To Arrange the Spectrochemical Series of the en, C5H7O2 and Cl
-
As Spectrachemical series depends on the Wavenumbers of different molecules/ Complex, -
-
so the Spectrochemical series would be en > C 5H7O2 > Cl
Conclusion:
:
From the above Calculation, the Tris(ethylenediamine)chromium(III) Chloride in Part A was collected as Fiber-liked Yellowish-orange solid, and its weight was 0.186g. The percentage yield of it was 7.49%. For the Tris(2,4-pentanedionato)chromium(III), it was collected as shiny purple powder and its weight was 0.541g. The percentage yield of it was 77.14%. The long Wavelength of Cr(en) 3Cl3•3H2O, Cr(C5H7O2)3 and CrCl3•6H2O were found to be -1
21459.2275, 17543.8597 and 15822.7848 cm respectively. Their Molar Absorptivities of them were -1
-1
found to be 25.6, 102.86 and 24.4 M cm respectively. -
-
The Spectrochemical series would be en > C 5H7O2 > Cl
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