Fabricating a Low-Cost, Simple, Screen Printed Paper Towel-Based Experimental Device to Demonstrate the Factors Affecting Chemical Equilibrium and Chemical Equilibrium Constant, K_c

Abstract

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.

The air-gap PAD: a roll-to-roll-compatible fabrication method for paper microfluidics

“…The current method, however, is applicable not only to our two device designs, the paper titrator 12 and the 12-lane PAD, 11,15,17,19,21,81,85,88 but also to the many PADs reported by other groups that involve spot tests and/or straight channels. 6,8,36,44,52,55,64–66,74,89–95…”

Equilibria of complexes in the aqueous cobalt(II)–N-(2-hydroxybenzyl)phenylalanine system and their biological activity compared to analogous Schiff base structures

“…The study of chemical equilibria provides an insight into the nature of aqueous systems by understanding the dynamics taking place in solutions [1] . Equilibrium systems provide an insight into the types of complexes formed depending on the pH of the environment, which will enable the identification of structures with potential biological properties.…”

Smartphone-Assisted Colorimetric Determination of Iron Ions in Water by Using Anthocyanin from Ruellia tuberosa L. as a Green Indicator and Application for Hands-on Experiment Kit

“…An LED light (65 W) installed in a commercial control lightbox is also necessary for improving and controlling constant illumination inside the lightbox. These adjustments can help with the reliability of the colorimetric results’ interpretation …”

“…These adjustments can help with the reliability of the colorimetric results' interpretation. 53 In this work, anthocyanin was extracted from a new source of Ruellia tuberosa L. for quantitative analysis of Fe 3+ in water. The colored complex of Fe 3+ −anthocyanin was monitored on a homemade 24-well plate using a smartphone under a control lightbox equipped with a 65-W LED light.…”