Experimental Procedure
The present laboratory study was based on an experiment in which different salts were subjected to combustion to investigate their electronic configurations by flame color. Specifically, the experiment involved seven active metal salts, each of whose solutions had a concentration of 0.1M: NaCl, KCl, CaCl2, SrCl2, BaCl2, CuCl2, and ZnCl2. A nichrome wire was dipped sequentially into each solution and ignited; the flame’s color was recorded for further analysis.
Observation
For each of the seven solutions, qualitative flame color studies were performed on the nichrome wire dipped into each solution. The results of the laboratory observations are shown in Table 1 below. As can be seen, the flame color of each of the seven solutions differed, although some similar hues, like that given by CaCl2 (brick red) and SrCl2 (carmine red), were noticeable.
Table 1. Results of qualitative observation of flame color for the seven solutions.
Results and Discussion
The present study aimed to investigate the flame color of seven different solutions. Under conditions where test tubes are unsigned, the flame test is a good yet reasonably easy-to-use qualitative identification tool to determine the nature of a substance. The present work’s advantage was that each solution had the same anionic composition and chlorides. Hence, the differences consisted only in the cations, which facilitated the identification procedure.
It was found that each of the solutions had different flame colors, as shown in Table 1. The presence of Na+ cation was responsible for the deep yellow color, K+ characterized the bright purple color of the flame, Ca2+ ion was characterized by brick red color, and Sr2+ was characterized by carmine red color. In addition, Ba2+ in solution gave a yellowish-green flame coloration, Cu2+ resulted in a bluish-green color, and Zn2+ was responsible for the white-yellow flame. From the experiment setup, one would expect that the presence of these cations with other anions would lead to the same results since it is the cation responsible for the flame coloration.
Variations in flame color depending on the nature of the cation are explained by the electronic configuration of specific atoms. In particular, in metals, the energy levels are arranged relatively densely, which favors a comparatively easy transition of electrons between them. When heated, electrons receive a large amount of energy, allowing them to transition to higher energy levels (LT, 2022).
Over time, however, heat energy can reduce in intensity, causing electrons to return to lower levels: the stored energy of such a transition is expressed in the perception of color. In other words, the flame color of different cations is due to the nature of their electronic configurations, which, due to differences in the placement of energy levels, number of electrons, and intensity of transitions, creates different flame colors. The flame coloration of metal solutions can be a good qualitative identification test.
Conclusion
Outcome
The present work was based on a qualitative identification test of metal solutions using flame color as an indicator. Seven solutions of different cations (Na+, K+, Ca2+, Sr2+, Ba2+, Cu2+, Zn2+) were used, which gave different colors of coloration when burned. This confirmed the hypothesis that the combustion test would give different results for each solution since the cationic nature of these cations is different.
Sources of Error
Several sources of potential error could have affected the accuracy of the test in the laboratory work performed. First, flame color is somewhat subjective; different people may perceive this indicator differently. Second, it cannot be ruled out that the prepared salt solutions may have been insufficiently pure and may have impurities that could affect the accuracy of the results.
Reference
LT. (2022). Electronic spectroscopy – interpretation. Libre Text Chemistry. Web.