Assembling and Using an LED-Based Detector To Monitor Absorbance Changes during Acid–Base Titrations
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Willy G. Santos [1] ; Éder T. G. Cavalheiro [1]
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[1] Universidade de São Paulo
Universidade de São Paulo
Brasil
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- Localización: Journal of chemical education, ISSN 0021-9584, Vol. 92, Nº 10, 2015, págs. 1709-1715
- Idioma: inglés
- Texto completo no disponible (Saber más ...)
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Resumen
A simple photometric assembly based in an LED as a light source and a photodiode as a detector is proposed in order to follow the absorbance changes as a function of the titrant volume added during the course of acid–base titrations in the presence of a suitable visual indicator. The simplicity and low cost of the electronic device allow the students to easily assemble the photometer and use it as a titration detector. The choice of the appropriate LED color should also demonstrate the principles of complementary colors. Concepts of data handling and relationship between the pH of the titration end point and indicator choice can be addressed. Errors associated with the use of wrong indicators can be demonstrated. The circuit assembly can highlight for the students the instrumentation and automation importance in modern chemical analysis. The discussion can be extended to relevant issues involved in this matter, such as light absorption, circuit analysis, and the hydrolysis concept, once they are involved and are closely related with the results obtained.
