The two possible balanced reactions are – Cuscus (aqua) + Fee(s) Cue(s) + Feces (aqua) [I] cuscus (aqua) + fee(s) ICC(s) + [II] Through the possible reactions, one of the best way to determine which one is the correct reaction pertaining to the lab is limiting reagent analysis, where mass of copper is quantitatively determined or by observations. Through the process of weighing by difference as suggested by the lab manual, anhydrous copper sulfate and iron powder were weighed out. Anhydrous copper sulfate was then dissolved in water on a hot plate and iron was added after the solution of copper sulfate had cooled down to room temperature.
The addition of iron took place under the fume hood so as to avoid inhalation of sulfur fumes which were leased as a side-product of this reaction. Copper precipitate was then collected by the use of a vacuum filtration setup. The copper precipitate was collected in a sintered glass crucible and mathematical analysis allowed for determination of the correct reaction amongst the two possibilities. In this lab, iron is being oxidized and this property of iron also allows for the reduction of other types of compounds such as intro aromatic compounds such as intermittent.
The lab had several indeterminate errors which cannot be controlled by the student and generally results from the inaccuracy of the equipment being used in the experiment. In this lab, the use of analytical balances was a major one and even something as accurate as analytical lances has some slight inaccuracy or uncertainty which is В±O. Egg. Another indeterminate error was the measuring of wash volumes within the graduated cylinders which have an uncertainty of В±0. Ml.
These uncertainties could have affected the end result allowing lower percent yield as suggested by Table 5 and calculation [VI]. The lab also had several possible determinate errors which are a result of the errors caused directly by the student. One of the more possible determinate errors was that there was some sort of static interference with the analytical balance. One of the students using the analytical balance could have ad a glove or phone nearby which acts in turn as a source of static interference and throws off the measurements of the analytical balanced.
Wrong measurements given by the analytical balance could result in a lower percent yield as calculated in [VI] by the student. Another largely possible determinate error is an error while transferring the liquid solution with copper precipitate within the solution. Improper quantitative transfer like splashing the liquid out of the glass crucible or the solution overflowing the crucible could result in a loss of suspended particles of copper precipitate. Loss of copper precipitate would result in a lower mass recorded by the analytical balance which in turn would result in a lower percent yield.
When iron was added to the copper sulfate solution, a light greenish-blue color was noticed within the solution. The species present in the solution are Fee+, SASS-, and Cue and after a little research, the light greenish blue color notices could be attributed to the presence of Feces crystals which are known as green copperas as when they dissolve they form a pale green solutions. As stated before, limiting reagents is a key concept within his lab as the reaction of Iron and Copper Sulfate can result in two different products through two different Equations [l] & [II].
It was up to the student to figure out which of the two equations pertained to the lab. This was done by determining the amount of moles of Cue obtained theoretically through the masses of copper sulfate and iron. Whichever reagent resulted in the fewer amount of copper moles produced will be the limiting reagent and the amount of moles produced would be the theoretical yield for that particular reaction. 3 An Introduction to Chemical Systems in the Laboratory, Hayden-McNeil, University of Illinois, Urbana-Champaign, 2012, Pig. 1 Donaldson, Ian, How to make Copperas (Iron Sulfate) from Pyrites, Encyclopedia Chemistry, http://www Salutatorian. Com/encyclopedia/chemistry/copperas. HTML (accessed 9/29/12) In this experiment however, the limiting reagent and reagent in excess is easy to determine mostly due to the visual clues. Copper sulfate is a brilliant blue color in solution and after the reaction has gone to completion, the blue color is still present within the solution proving that the reagent in excess is copper sulfate and the limiting reagent in this experiment is iron.
In the experiment, however the student is able to find the mass of the copper precipitate by knowing the mass of the reagents and equipment as in Table 1 and Calculation [l]. By knowing the mass of the copper precipitate, the student was able to calculate the moles of copper formed (Calculation [l l]) and then compare it to the theoretical yield in order to get the percent yield as in Table 5. By comparing the theoretical yield of both Equations [l] and [II] with the actual yield, the student was able to determine that iron was the limiting reagent and that Equation [I] was the main action, in addition to Calculation [Ill].
This lab was successful mostly because the student was able to determine the limiting reagent through the means of quantitative and limiting reagent analysis. This experiment allowed the student to further understand redo reactions in addition to determining that iron was the limiting reagent. Further research can be undertaken into the study of elements that can displace iron much more effectively as iron is capable of displacing various dangerous elements and compounds but even iron in large quantities is not desired. References: by Zero-Valet Iron Metal, Environ.