Validation of the Nernst equation and an equation that estimates the mass of calcium hydroxide for a given pH

Aranguri-Llerena G.; Huarcaya-Mendoza N.J. · Educacion Quimica (2024) · DOI: 10.22201/fq.18708404e.2024.2.86430

Resumen

Calcium hydroxide (Ca(OH)2) is used in multiple industrial applications and as a pH modifier. This work aimed to experimentally validate the Nernst equation, using Ca(OH)2 dissolutions and to develop a didactic suggestion for chemical education, which allows finding the necessary mass of Ca(OH)2 that must be added to a certain volume of water to reach a required pH. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron imaging (SEM) analyses were performed to characterize Ca(OH)2. The results of the tests at 27.5°C ± 0.1°C show that when plotting the values of pH experimental (pHe), potential (E) and conductivity against the concentrations of hydroxyl anions [OH-] (semilogarithmic), follow the same pattern, affected by the low solubility of Ca(OH)2 in such a way that the last zone of the three graphs tends to be parallel to the axis of the [OH-] concentrations. The equation was generated: E = 369.55 - 58.914 pHe; where 58.914 represents the value of its slope, which is equivalent to 99.58% of the theoretical slope of the Nernst equation and an equation was found that estimates the mass of Ca(OH)2 that must be added to a volume of water, to reach a required pH.

Instituciones: Universidad Nacional de Trujillo