This work reports the first use of
rubber latex waste as the hydrophobic
reagent for a low-cost, simple, and rapid fabrication of a paper towel-based
experimental device (PTED) with a circular design of 5 mm to demonstrate
the factors affecting chemical equilibrium; this serves as a user-friendly
means for a laboratory experiment. The illustration of the factors
affecting chemical equilibrium is implemented in the PTED. In this
approach, the color change of a cobalt(II) complex reaction from pink
to blue was observed by the naked eye on the PTED when a tiny drop
of hydrochloric acid solution and the treatment of heat by using a
hot air dryer (1200 W, 2 min) were applied to the PTED with the precoated
cobalt solution (pink color), separately or together. The return of
the color of the reactions from blue to pink was carried out by using
a tiny drop of water and the treatment of cooling by using an ice
bath for 10 min. In addition, the chemical equilibrium constant (K
c) can be easily quantified by processing digital
images of the detection zones of PTED captured with a smartphone camera
under a control light box at room temperature (≈25 °C),
while image analysis was performed using ImageJ software. This PTED
laboratory is a new approach not only to enhance students’
learning of the factors affecting chemical equilibrium based on Le
Châtelier’s principle, but also to present potential
applications of PTED into all levels of chemistry from middle school
through college classes.
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