The chemical element of Fe2+ - Essay Example

Here in, an unknown concentration of Fe2+ is determined by the potentiometric titrations. Initially, diluting(NH4)2Ce(NO3)6 Ceric (IV) ammonium nitrate with concentrated sulfuric acid in conjunction with nanopure water, forms a standard Ce4+solution. 0.095 +-0.001M is the exact concentration of the solution above. Furthermore, after three titrations with FeSO4.7H2O, the solution Ce4+ comes to standard. In addition, 1M HCL, and nanopure water forms its dissolving agent. According to low accuracy and the hastiness of the first titration, it is hence not noted. 0.086+-0.001 is the fraction of Fe2+ in unknown. Both Fe2+ and Ce4+ are titrated under the action of electrode. Following the above,Ce4+ went through a reduction process since it was a cathode and so, it gained an electron to Ce3+.on the other hand, since Fe2+ is an anode, where oxidation takes place and became Fe3+ after loosing and electron. Values and half reactions is as below: Potential estimation at the end of titration is by Nernst equation. Notably, the potential equivalence point comes in by addition of two Nernst equations. It is pertinent to note that, each solution has its own potential. Estimation of electrode potential at the end- point is possible, and it is by using the Nernst equations and the formal potential values. Furthermore, referencing electrode plays a vital role in estimating the potential that is crucial for reference electrode (1)’s potential. Concentrated sulfuric acid is diluted by nanopure water in 250 mL flask that had 13.7009g (NH4)2Ce(NO3)6 to form Ce4+ solution.1M HCl dilutes about 0.5g of FeSO4.7H2O that is measured three times to standardize Ce4+ solution from three Fe2+ solutions. End- point calculation is done from the records on the voltmeter for each titration. Nanopure water and a factor of 4 with 1M HCl dilutes unknown measured mass. Hence, the unknown undergoes titration three times using Ce4+ solution. Recordings from voltmeter make it possible for the use of end-point calculation, and Fe2+ concentration in the unknown (2). Ce4+ solution preparation Actual weight of ceric (IV) ammonium nitrate undergoes division by the molecular weight with the final volume of the solution to come up with Ce4+ concentration that is expected. Equation (1) and the table (1) numeric values are essential in calculation of the Ce4+solution, expected to be 0.100M in concentration. 1M HCl preparation Since only 12M HCl is given, then nanopure water aids in preparing the 1M HCl by dilution. Notably, results from equation (2) evident the preparation of 1.00M,HCl concentration. Standardization titration Hereby, only two titrations that is slow is counted out of the three in process. Data from the second titration is revealed in the figure 1 and table 3.Volume is calculated using both equation (3) and (4) and first voltage derivative respectively. Slope of the voltage represents the value of the first derivative throughout the whole titration. Moreover, the end-point on titration graph coincides to the maximum point of the first derivative graph. Following this, it is easy and clear to find the end- product of titration. However, the end-point on the titration graph is the same as the maximum point on first derivative graph. Following this, 19.1mL of Ce4+ in solution forms end-point, which is in red in the table and again represented by red arrow on the graph 1. Standardization results of titrations are shown in the table 4. Primarily, equation (3) was used to calculate the volumeend-point.. Since, the number in the voltmeter did not stabilize as soon as endpoint did pass during titrations. Therefore, because of that, the voltageendpoint was not consistence. Besides voltage is recorded too late on the third titration, and early on the first titration. In addition, there was neglect in the weighing error. Titration of the unknown Fe (II) solution 12.05 Ml of Ce4+ solution is enough to peak the endpoint in each titration, with three titrations of the unknown. Concentration of Ce4+ solution Initially, a small amount of Ce4+ is added to Fe2+ solution, and the number of moles Ce4+ did increase in Fe2+ solution gradually with the continues addition of Ce4+. However, the increase of Ce4+ was persistent until the number of moles of Ce4+ and Fe2+ came to equilibrium. Following this, at endpoint, the moles of Fe2+ are divided with Ce4+ solution used and hence the establishment of Ce4+ concentration at endpoint. Furthermore, mean values of Vceend-point and nFe2+ are used in equation (5).Notably; the following equations did calculate the uncertainties of VCeendpoint and the [Ce4+]. VCeendpoint uncertainty is +-0.0002L, and in calculations 0.095M was in [Ce4+] but had uncertainty of +-0.001M.However, this is a close value to the weight of (NH4)2Ce(NO3)6 which is 0.100M in the concentration of Ce4+.Standardization of the solution is not necessary since the difference between the two values is negligible. Mass fraction of Fe in the unknown After dissolving in 100mL of 1M HCl solution, the solution was exactly pipette in 25mL for titration. On other hand, 50ML of nanopure water did dissolve each aliquote. Initially, the number of Fe2+ moles in the unknown is calculated by multiplying the dilution factor (4), with the number of moles of Ce4+. Note that, the numbers of moles of Fe2+ is analyzed, as well as the number of moles of Ce4+, and then multiplied by diluting factor, which is 4 as affirms ( Kotz, Treichel 125). The results show that Fe2+ had 4.58*10-3 in the unknown solutions. Furthermore, endpoint volume of Ce4+ solution’s uncertainty is found using 6th equation which is +-0.0001L. Measuring errors that is in Valiquote, massunknown and Vdissolved is neglected. Equation (10) is vital in calculation of the fraction weight of the Fe2+. Mass of Fe2+ that is contained in the unknown can be calculated by multiplying its molar mass with the number of moles in Fe2+. On the other hand, division of calculated mass by the total mass of unknown, which is the weight fraction, is found, to be 0.086. Using propagation of the errors in calculation, the uncertainty is +-0.001, clearly shown in the equation (11). Nernst equation Coming at the endpoint of titrations, Nernst equation is used to estimate the voltage, which occurs at the endpoint of all the titrations. Concentration of Fe2+ is noted to be equal to Ce4+ at the end point; furthermore, the Ce3+ was equal to Fe3+.As a result, the summing of the two equations,E0Fe3+/Fe2+ and E0Ce4+/Ce3+ mean value occur to be potential that comes in at the end point. However, after summing the two equations, mean of the two formal potentials was at the end- point. In table (4), mean value of the measured potential is 0.896V, unlike the expected potential that is to be 0.84V.Therefore, there is no significance in comparing the two equations. Finally, it is important to note that, Nernst equation is suitable in calculating the titrations’ endpoint in expected potential. Work cited Kotz, John and Treichel, Paul. Chemistry & Chemical Reactivity. New York: Cengage, 2009. Read More