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Determination of chemical equilibrium constant of thiocyanatoiron(iii) ion complex using a colorimetric analysis of smartphone-captured images as an alternative method for high school chemistry a) Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Warin Chamrap, Ubon Ratchathani, Abstract This study is aimed to develop an alternative method for determination of the chemical equilibrium constant (K_{c}) of thiocyanatoiron(III) ion complex based on colorimetric analysis of smartphone-captured images. The various images of the ion complex captured by iPhone 6S plus and Xiaomi Redmi 8 smartphones were processed using ImageJ software in order to determine the K_{c} using a standard plot between blue color intensity and -log[Fe(SCN)]^{2+} It was found that the K_{c} were 212.007±23.95. The Kc obtained from the standard UV-Visible spectrophotometry was 218.382±6.85. The paired samples t-test analysis at the 95% significance level (p<0.05) indicated that the Kc obtained from both smartphones and the standard method were not statistically different. This experiment was implemented as an experiment for one classroom of grade-11 students at a regular public school in Thailand. The students worked in groups of 5 students and spent two hours to complete the experiment. Their determined K_{c} were in the range of 200 - 250, which consistent with our preparation result. It was found that the students obtained post-achievement test score (mean 8.43, S.D. 0.90) statistically higher than pre-achievement test score (mean 4.43, S.D. 0.97) at the 95% significance level (p<0.05). These students commented that this experiment was easy to perform and they enjoyed using their smartphone in studying chemistry. Keywords: chemical equilibrium constant- colorimetric analysis- high school chemistry- smartphone-assisted experiment Topic: Chemistry Education |
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