Absorbance of light by a transition metal complex investigation Essay

initiationCommonly known as transition metals, d block elements perk up partially filled d sublevels in one or to a greater extent than 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 symptomatic properties such as multiple oxidation states, king to form tortuous ions, colou ceriseness compounds and good catalytic properties. In terms of unsettled oxidation states, d block elements usually have a +2 oxidation good turn which corresponds to the loss of the deuce 4s electrons (as it is easier to stand the 4s electrons than the 3d electrons). Transition metals prat have variable oxidation states because the ionization energies al outset for up to two 3d electrons to be lost.Because transition metals argon relatively small in size, the transition metal ions draw out species that are rich in electrons ligands (neutral molecules or ban ions that contain non-bonding pair of elect rons which when covalently bonded with and form compound ions. Because the d orbitals usually split up into two groups (high and low) in transition metal complex ions, the energy compulsory to promote a d electron into the high split level corresponds with a particular wavelength in the visible region, which is absorbed when unused passes by means of the complex ion. Transition metal usually then exhibits the be energy/light the completing colour.In this investigation, the disparate absorbance of these coloured responses lead be investigated by alter the number of moles of the transition metal in the theme. agree to the Beer-Lambert law, absorbance is directly proportional to the dumbness and that thither is a logarithmic dependence in the midst of the absorbance and the intentness of the substance, this kind is as shown in figure 1 and 2.In the graph representation of the Beer-Lambert law, the logarithmic relationship enkindle evidently be adoptn as the concen tration of the solution appends, the calibration curve becomes less linear and more flat. This is probably referable to the saturation of colour of the solution. In plyition, the graph also indicates that the relationship starts at the pedigree and is generally linear at lower concentrations.In this investigation, Nickel (II) Sulphate will be utilize as the transition metal and H2O will be used as the ligand. The complex ion form will therefore be a hexaaqua atomic number 28(II) complex ion, Ni (H2O) 6 2+. It has a coordination number of 6 and is of an octahedral shape. (Microsoft Encarta, 2007)AimTo investigate how the concentration of hexaaquanickel(II) ions (Ni (H2O) 6 2+) in solution affects the absorbance of red light (660nm) by criterion it with a colorimeter.HypothesisAs the concentration of hexaaquanickel(II) ions increases, the absorbance of red light1 will also increase. This is so because as verbalize in the Beer-Lambert law, the absorbance of light is directly pro portional 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 therefore an increase absorbance at higher concentrations. In addition, condescension the logarithmic relationship, I promise my selective information 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 free be evident.Variables free Concentration of hexaaquanickel(II) ions (0.0313mol, 0.0625mol, 0.125mol, 0.250mol, 0.500mol)Dependent Absorbency of red light (660nm)Controlled strength of solution (25cm per different mol solution)EquipmentMethod1) standard 6.57g of nickel sulphate with an electronic balance and manoeuver in a 250cm beaker2) Measure 50cm of deionised irrigate system wit h 50cm measuring cylinder and pour into the 250cm beaker with the nickel sulphate to compel a 0.5mol nickel sulphate solution3) mixture the solution thoroughly with a glass displace rod, make sure the solution is transparent ( non murky) and no remnants of the nickel sulphate should be present in the solution4) Label the five 50cm volumetric flasks 0.03125mol, 0.0625mol, 0.125mol, 0.25mol and 0.5mol5) pipette 25cm of the previously made nickel sulphate solution from the 250cm beaker and place into volumetric flask labelled 0.5mol6) pipet a nonher 25cm from the beaker and place into volumetric flask denominate 0.25mol7) Measure and pipette 25cm of deionised pissing and add into 0.25mol8) cock thoroughly9) Measure and pipette 25cm from 0.25mol and add into 0.125mol10) accept steps 7 to 8 but add the water into 0.125mol11) Measure and pipette 25cm from 0.125mol and add into 0.0625mol12) resort step 10 but add into the water 0.0625mol13) Measure and pipette 25cm from 0.0625mo l and add into 0.0313 mol14) reprise step 10 but add into the water0.0313mol15) Connect the PASPORT colorimeter to the computer16) Select to vizor red (660nm) absorbance17) After all five solutions have been made, label five cuvettes the akin labels as the volumetric flasks (place on lid, careful non to have any(prenominal) of the label on the cuvette itself)18) Fill each tagged cuvette with its corresponding volumetric flask label with a dropper19) Fill the remaining unlabeled cuvette with water20) Place the cuvette with water into the colorimeter and press young button to calibrate, do not do anything until the spirt light switches off by itself21) Place the cuvette labeled 0.03125mol into the colorimeter press start and stop later on getting a constant reading22) remember the data23) Repeat steps 21-22 until all labeled cuvettes have been measured for red absorbanceData display panelConcentration / mol dm-Red light (660nm) absorbanceUncertaintiesUncertainties (cm3) me asuring rod cylinder1.0cmBulb pipette0.06 cmelectronic weigh0.01gConcentration (mol/dm)UncertaintyGraphs word and ConclusionIt can be seen from the graph that there is a linear relationship between the measurement of red light absorbed and the concentration of hexaaquanickel(II) ions. It can also be deduced that as the concentration increases, the red light assiduity increases at twice the rate. However, it is fire 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) abso rption. 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.EvaluationOne aspect I can improve my method is using the same cuvette and in the same direction each clock for measuring all the different solutions, as it has been celebrated that the cuvettes we have been currently using are not perfectly constructed and may differ with the distan ce as light passes through. This will help improve the truth 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). some other aspect was in the preparing the different solutions, because I had dilute each solution using the same solutions from before, so the uncertainty of each would naturally continuously figure up (final uncertainty of 4.31%) for example, if I had accidentally created a 0.052 mol nickel sulphate solution, then the beside solution I diluted from that solution would not be 0.025 mol as intended. One personal manner to see through this limitation is to perhaps seduce each solution separately to avoid a build up of uncertainties.In addition, another way of life to make this investigation more conclusive and luxuriant could be increasing the different amounts of concentration of the nickel sulphate solution, as I only had 5 different concentrations.BibliographyClark, J. (2007). The Beer-Lambert law. In Absorption spectra. Retrieved January 15, 2008, fromhttp//www.chemguide.co.uk/analysis/uvvisible/beerlambert.htmlMicrosoft(r) Encarta(r) Online Encyclopedia. (2007). Complex. Retrieved January 17, 2008, fromhttp//au.encarta.msn.com/encyclopedia_781538720/Complex.htmlNeuss, G. (2007). determine the concentration of an element. In Chemistry course bloke (p.276). Oxford University Press.1 Because nickel sulphate solution is parkland in colour, red light will be used to measure the absorbency of the solution as it is the complementary colour.