Absorbance of light by a transition metal complex investigation Essay Example for Free

Absorbance of light by a transition metal complex investigation Essay Introduction Commonly known as transition metals, d block elements have partially filled d sublevels in one or more of their oxidation states. It is in the first row of transition elements that the 3d sub-level is incomplete. These d block elements show certain characteristic properties such as multiple oxidation states, ability to form complex ions, coloured compounds and good catalytic properties. In terms of variable oxidation states, d block elements usually have a +2 oxidation number which corresponds to the loss of the two 4s electrons (as it is easier to lose the 4s electrons than the 3d electrons). Transition metals can have variable oxidation states because the ionization energies allow for up to two 3d electrons to be lost. Because transition metals are relatively small in size, the transition metal ions attract species that are rich in electrons ligands (neutral molecules or negative ions that contain non-bonding pair of electrons which when covalently bonded with and form complex ions. Because the d orbitals usually split up into two groups (high and low) in transition metal complex ions, the energy required to promote a d electron into the higher split level corresponds with a particular wavelength in the visible region, which is absorbed when light passes through the complex ion. Transition metal usually then exhibits the remaining energy/light the complementary colour. In this investigation, the different absorbance of these coloured solutions will be investigated by varying the number of moles of the transition metal in the solution. According to the Beer-Lambert law, absorbance is directly proportional to the concentration and that there is a logarithmic dependence between the absorbance and the concentration of the substance, this relationship is as shown in figure 1 and 2. In the graph representation of the Beer-Lambert law, the logarithmic relationship can evidently be seen as the concentration of the solution increases, the calibration curve becomes less linear and more flat. This is probably due to the saturation of colour of the solution. In addition, the graph also indicates that the relationship starts at the origin and is generally linear at lower concentrations. In this investigation, Nickel (II) Sulphate will be used as the transition metal and H2O will be used as the ligand. The complex ion formed will therefore be a hexaaquanickel(II) complex ion, Ni (H2O) 6 2+. It has a coordination number of 6 and is of an octahedral shape. (Microsoft Encarta, 2007) Aim To investigate how the concentration of hexaaquanickel(II) ions (Ni (H2O) 6 2+) in solution affects the absorbance of red light (660nm) by measuring it with a colorimeter. Hypothesis As the concentration of hexaaquanickel(II) ions increases, the absorbance of red light1 will also increase. This is so because as stated in the Beer-Lambert law, the absorbance of light is directly proportional to the concentration. Furthermore, as the concentration increases, there are more molecules of the complex ions within the solution to interact with the light that is being transmitted hence an increased absorbance at higher concentrations. In addition, despite the logarithmic relationship, I expect my data to show a linear relationship instead because the number of moles I am measuring red absorbance against is rather low (maximum 0.5 moles), so while it would be insufficient to see the clear logarithmic curve; the linear increase in the beginning would still be evident. Variables Independent Concentration of hexaaquanickel(II) ions (0.0313mol, 0.0625mol, 0.125mol, 0.250mol, 0.500mol) Dependent Absorbency of red light (660nm) Controlled Volume of solution (25cmà ¯Ã‚ ¿Ã‚ ½ per different mol solution) Equipment Method 1) Measure 6.57g of nickel sulphate with an electronic balance and place in a 250cmà ¯Ã‚ ¿Ã‚ ½ beaker 2) Measure 50cmà ¯Ã‚ ¿Ã‚ ½ of deionised water with 50cmà ¯Ã‚ ¿Ã‚ ½ measuring cylinder and pour into the 250cmà ¯Ã‚ ¿Ã‚ ½ beaker with the nickel sulphate to create a 0.5mol nickel sulphate solution 3) Mix the solution thoroughly with a glass stirring rod, make sure the solution is transparent (not murky) and no remnants of the nickel sulphate should be present in the solution 4) Label the five 50cmà ¯Ã‚ ¿Ã‚ ½ volumetric flasks: 0.03125mol, 0.0625mol, 0.125mol, 0.25mol and 0.5mol 5) Pipette 25cmà ¯Ã‚ ¿Ã‚ ½ of the previously made nickel sulphate solution from the 250cmà ¯Ã‚ ¿Ã‚ ½ beaker and place into volumetric flask labeled 0.5mol 6) Pipette another 25cmà ¯Ã‚ ¿Ã‚ ½ from the beaker and place into volumetric flask labeled 0.25mol 7) Measure and pipette 25cmà ¯Ã‚ ¿Ã‚ ½ of deionised water and add into 0.25mol 8) Mix thoroughly 9) Measure and pipette 25cmà ¯Ã‚ ¿Ã‚ ½ from 0.25mol and add into 0.125mol 10) Repeat steps 7 to 8 but add the water into 0.125mol 11) Measure and pipette 25cmà ¯Ã‚ ¿Ã‚ ½ from 0.125mol and add into 0.0625mol 12) Repeat step 10 but add into the water 0.0625mol 13) Measure and pipette 25cmà ¯Ã‚ ¿Ã‚ ½ from 0.0625mol and add into 0.0313 mol 14) Repeat step 10 but add into the water0.0313mol 15) Connect the PASPORT colorimeter to the computer 16) Select to measure red (660nm) absorbance 17) After all five solutions have been made, label five cuvettes the same labels as the volumetric flasks (place on lid, careful not to have any of the label on the cuvette itself) 18) Fill each labeled cuvette with its corresponding volumetric flask label with a dropper 19) Fill the remaining unlabeled cuvette with water 20) Place the cuvette with water into the colorimeter and press green button to calibrate, do not do anything until the green light switches off by itself 21) Place the cuvette labeled 0.03125mol into the colorimeter press start and stop after getting a constant reading 22) Record the data 23) Repeat steps 21-22 until all labeled cuvettes have been measured for red absorbance Data Table Concentration / mol dm-à ¯Ã‚ ¿Ã‚ ½ Red light (660nm) absorbance Uncertainties Uncertainties (cm3) Measuring cylinder à ¯Ã‚ ¿Ã‚ ½1.0cmà ¯Ã‚ ¿Ã‚ ½ Bulb pipette à ¯Ã‚ ¿Ã‚ ½0.06 cmà ¯Ã‚ ¿Ã‚ ½ Electronic weigh à ¯Ã‚ ¿Ã‚ ½0.01g Concentration (mol/dmà ¯Ã‚ ¿Ã‚ ½) Uncertainty Graphs Discussion and Conclusion It can be seen from the graph that there is a linear relationship between the amount of red light absorbed and the concentration of hexaaquanickel(II) ions. It can also be deduced that as the concentration increases, the red light absorption increases at twice the rate. However, it is interesting to note that the line of best fit does not start at the origin, but at (0, 0.0623) as the equation derived from the line of best fit states, suggesting that despite showing a clear linear trend, my data is precise but not accurate. This is possibly due to equipment imperfection, for example the cuvette, which will be discussed in the evaluation. However, it is still evident that, as stated in my hypothesis, as the concentration increases, the chances of light interacting with the complex ion molecules also increase, hence yielding a higher light (red, in this case) absorption. While it is true that the Beer-Lambert law states the relationship between concentration of a substance and its absorbency has a logarithmic relationship, my data is linear because the concentrations of my tested solutions were rather low, so if I were to continue my experiment and create more concentrated nickel sulphate solutions, I would expect to see the curve become non-linear as concentration increases because the solution will eventually become saturated. Therefore, in conclusion, my hypothesis corresponds with the results: the relationship between red absorbance and concentration of hexaaquanickel(II) ions is quite clear as the concentration increases, the red absorbance also increases. Evaluation One aspect I can improve my method is using the same cuvette and in the same direction each time for measuring all the different solutions, as it has been noted that the cuvettes we have been currently using are not perfectly constructed and may differ with the distance as light passes through. This will help improve the accuracy of the results and an important aspect to take into consideration, because also stated in the Beer-Lambert law, the length in which the light passes through also makes a difference in the absorption of light (the longer the container is, the more chances of light interacting with the molecules of the solution). Another aspect was in the preparing the different solutions, because I had diluted each solution using the same solutions from before, so the uncertainty of each would naturally continuously build up (final uncertainty of 4.31%) for example, if I had accidentally created a 0.052 mol nickel sulphate solution, then the next solution I diluted from that solution would not be 0.025 mol as intended. One way to see through this limitation is to perhaps prepare each solution separately to avoid a build up of uncertainties. In addition, another way to make this investigation more conclusive and detailed could be increasing the different amounts of concentration of the nickel sulphate solution, as I only had 5 different concentrations. Bibliography Clark, J. (2007). The Beer-Lambert law. In Absorption spectra. Retrieved January 15, 2008, from http://www.chemguide.co.uk/analysis/uvvisible/beerlambert.html Microsoft(r) Encarta(r) Online Encyclopedia. (2007). Complex. Retrieved January 17, 2008, from http://au.encarta.msn.com/encyclopedia_781538720/Complex.html Neuss, G. (2007). Determining the concentration of an element. In Chemistry course companion (p. 276). Oxford University Press. 1 Because nickel sulphate solution is green in colour, red light will be used to measure the absorbency of the solution as it is the complementary colour.

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Anne Frank also known as Annelies Marie Frank was a sixteen year old girl who got murdered during the Holocaust. She was born in the city of Frankfurt in Germany to her parents Otto and Edith Frank. Anne Frank had an older sister who was three years older than she was and her name was Margot Betti Frank. The Franks were known as a very liberal family who were also classified as a middle class family since their ancestors lived in Germany. In 1933 the Franks decided to move towards Amsterdam since Germany was being overruled by the Nazis. While the family had adjusted to Amsterdam, Otto Frank was really focused on his business since he was new into the city. Anne and Margot were also getting adjusted to the school system and when they were well adjusted they started to have friends who were Jewish and non Jewish. Six years later which was in 1939, Anne’s and Margot’s grandmother decided to join them in Amsterdam as well and be reunited with her two beautiful nieces. In M arch, 1940 a horrible trajedy happened Amsterdam which was that Amsterdam had been attacked by the Nazis who overrul...

Analysis of ‘The Death of a Moth” Essay

Virginia Woolf is a British writer born in 1882 and she died a horrific death in 1941. She jumped unto River Ouse wearing an overcoat filled with rocks. She committed suicide as she was depressed and has a pessimistic feeling towards life due to a mental illness she has been cursed with. She wrote ‘The Death of the Moth’ in 1942. This essay contains a wide variety of rhetorical devices that makes it intriguing. Although the essay is short, she wrote a detailed story with an underlying metaphor. In this non-fictional essay, she effectively conveys her ideas through the use of figurative language. She uses an extended metaphor in which the moth symbolizes humans in the way it lives its life. The essay entraps the reader into the outgoing struggle of our own mortality. Throughout the essay, the reader becomes aware of the tragedy that all life has to offer and that is the inevitable death. The theme is not lucid in the beginning. But in the latter part of the essay, one can deduce that the moth actually symbolizes humans and life. In the essay, she illustrates the struggle between life and death. Her purpose in writing this passage is to depict how pathetic life is in the face of death, and to garner respect for the awesome power that death has over life. Throughout the essay, death is described from many different angles. The purpose of this is to remind us of the power that death has over life. She shows us the death is certain and unavoidable. She does not convey this message with logic, but with instead with emotions, feelings, and implicit ideas. She makes us feel the death of the moth to impart us a more complete understanding of the eternal power of death. She uses several different types of figurative and literary language. As mentioned earlier, the essay is an extended metaphor. She used simile several times. For example, â€Å"†¦ until it looked as if a vast net with thousands of black knots in it had been cast up into the air. † In this simile, she describes a gathering of crows in the trees outside her window. In addition, she uses parallelism, which occurs when she writes: â€Å"That was all he could do, in spite of the size of the downs, the width of the sky, the far-off smoke of houses, and the romantic voice, now and then, of a steamer out at sea. † A good example of hyperbole is present when the author describes: â€Å"One could only watch the extraordinary effort made by those tiny legs against an oncoming doom which could, had it chosen, have submerged an entire city, not merely a city, but masses of human beings†¦ † By using such a simple creature’s struggle against death as a metaphor, Woolf creates a beautiful essay on the fragility of life. Her simplicity and detail keeps her essay from becoming overcomplicated, overly dramatic, or depressing. It was a surprisingly light and meaningful essay on an event that most people would probably overlook.

The War And The Reality Of War - 1943 Words

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