Ginafe Hisanan (20075015) 04/02/19
The Synthesis of Pentaamine Complex of Cobalt (III) Chloride
Aim
The aim of this experiment was to synthesize and determine the ratio of pentaamine complex of cobalt (III) chloride. Also, to investigate the complex through UV-Vis and IR analysis.
Introduction
The compound chloropentaamine cobalt (III) chloride is known as coordination complex which are, the compounds produced in between the transition metal ions and several types of organic and inorganic ions or neutral molecules. The ligands mean that any molecules or ions that are connected to the middle metal atom that will bind to central metal atom and generates a coordination complex. These ligands donate electron pairs to make bonds and can be a Lewis base while the metal ion would be a Lewis acid. Also, the ligand can be a factor that affects the oxidation state of the metal. Cobalt (III) produces stable and simple prepared coordination compound. The ligand exchange is fast, therefore this experiment had a fast reaction after the additions of the reagents used. Cobalt complexes are generated from oxidation of cobalt salt in the presence of a stabilizing ligand.
Equation 1: The equation of the synthesis.
Figure 1: The structure of pentaamine complex of cobalt (III) chloride.
Method
As per lab manual and all the reagents were measured in halves.
Results
1. Theoretical Yield
a. Mass of Ammonium Chloride
i. 6.15 g ÷ 54.489 g/mol = 0.1129 moles
b. Mass of Cobalt (II) Chloride Hexahydrate
i. 13.1 ÷ 237.9309 g/mol = 0.0551 moles
c. Limiting reagent: Cobalt (II) Chloride Hexahydrate
d. Molar mass of Chloro pentammine cobalt chloride
i. 250.445 g/mol ÷ 0.0552 moles = 13.80 g
2. Percentage Yield
a. Actual weight of complex ÷ theoretical yield
i. 8.063 g ÷ 13.80 = 0.5843
ii. 0.5843 x 100 = 58.43%
3. Table 1: Tabulated measurements for glass center funnel.
Flask A
Flask B
Initial mass of crucible
38.73 g
40.11 g
Final mass of crucible
39.05 g
40.58 g
Weight complex
0.2501 g
0.2507 g
Total complex
0.32 g
0.47 g
4. Number of moles of Cobalt
a. Actual weight ÷ molecular weight of Co(NH3)5Cl3
i. 0.2501 g ÷ 250.445 g/mol = 0.0001 moles (A)
ii. 0.2507 g ÷ 250.445 g/mol = 0.001 moles (B)
5. Number of moles of available Chloride
a. Weighed of crucible ÷ molecular weight of silver chloride
i. 39.05 g ÷ 143.32 g/mol = 0.2725 moles of AgCl (A)
ii. 40.58 g ÷ 143.32 g/mol = 0.2831 moles of AgCl (B)
6. Molecular ratio
a. CoCl3.5NH3
i. Co= ((1x 58.93) /238.33 g/mol ) x100 =24.7
ii. Cl = (( 3 x 35.45)/238.33 g/mol) x 100 = 44.6 %
iii. N = (( 5 x 14.01)/238.33 g/mol) x 100 = 29.4 %
iv. H = (( 3 x 1 ) / 238.33 g/mol) x 100 = 1.3%
7. Ratio of Cobalt : Available chloride : Total Chloride
a. : 0.2778 : 0.5556
8. UV spectra
Figure 2: The UV-Vis spectrum of complex showing two peaks. With max of at 523 nm and 358.9 nm and the absorbance at 0.917.
Discussion
First part of the experiment was the critical section of the synthesis as the reaction reacted quickly and...
