An Experimental Determination of Thermodynamic Values

Antony, Erling; Muccianti, Christine; Vogel, Tracy

doi:10.1021/ed200076v

Cited by 2 publications

(7 citation statements)

References 3 publications

(4 reference statements)

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“…[5][6][7][8][9][10][11][12][13] However, many of these analyses require instrumentation that may not be widely available to all laboratories, or require more sophisticated procedures that are unsuitable for an introductory audience. In the interest of bringing this concept to a broader group of students, an alternate methodology was developed to perform the analysis based on just the natural dissociation of the acid as determined by pH and temperature measurement.…”

Section: G H T S°°°∆ = ∆ − ∆ (2)mentioning

confidence: 99%

Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid

Rezsnyak¹

2017

WJCE

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The concepts of equilibrium and thermodynamics are among the most important topics covered in a general chemistry course. The thermodynamic properties ∆G°, ∆H°, and ∆S° are difficult to measure directly in a laboratory setting, but can be determined by monitoring the temperature dependence of the equilibrium constant, K. Previously published procedures require sophisticated technology or methodology, such as simultaneously measuring temperature and absorbance using a spectrophotometer, which may be unavailable to small and/or rural colleges and universities. Measuring the pH of a weak acid solution while varying the temperature allows for this analysis to be conducted simply, making it more accessible to broader range of academic laboratories. This experiment outlines the simple measurement of the equilibrium constant and temperature, with aspects of graphical analysis, allowing students to link the concepts of equilibrium and thermodynamics conceptually and mathematically. Calculated values of ∆G°2 98 are consistent with literature values, indicating that the experiment is suitably robust to be performed successfully by students of a wide range of skill levels.

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Section: G H T S°°°∆ = ∆ − ∆ (2)mentioning

confidence: 99%

Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid

Rezsnyak¹

2017

WJCE

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“…Equation is obtained by using the thermodynamic relationships between the standard Gibbs free energy change (Δ G °) with K eq (eq ) and with the enthalpy (Δ H °) and entropy (Δ S °) variations (eq ). , K e q = [ [ CoCl 4 ] 2 − ] false[ false[ normalCo false( normalH 2 normalO false) 6 false] 2 + false] [ Cl − ] 4 Δ G o = − R T ln K eq Δ G o = Δ H o − T Δ S o ln K eq = …”

Section: Introductionmentioning

confidence: 99%

“…The molar concentration of these compounds can be found from the Lambert–Beer law (eqs and ). A 520 nm = ε b false[ false[ normalCo false( normalH 2 normalO false) 6 false] 2 + false] A 690 nm = ε ′ b false[ false[ normalCoCl 4 false] 2 − false] where A is the absorbance, ε and ε′ are the molar absorptivities for each compound, and b is the cuvette length (optical path). Using UV–vis spectrophotometry, Antony et al obtained molar absorptivity (ε) of 552 L mol –1 cm –1 for tetrachlorocobalt(II) ion, with Δ H ° and Δ S ° of 54.6 kJ mol –1 and 84 J mol –1 K –1 , respectively.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The main novelties of this work lie in the use of digital imaging to estimate thermodynamic parameters and three-dimensional cubic model of the RGB system for analysis; the study also presents vector calculation, along with a step-by-step guide to obtaining thermodynamic data using spectrophotometry and DIB methods, where F and T statistical tests are used to evaluate the results obtained. , Furthermore, the study provides useful insights into building an LED-chamber, which is an interesting device used for all DIB applications. , Considering its low-cost and ease of portability, the proposed device can help boost knowledge transfer, allowing accessibility, social inclusion, popularization, and dissemination of science, mainly in poor communities. , …”

Section: Introductionmentioning

confidence: 99%

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Determination of Thermodynamic Parameters Using Digital Image-Based Method

dos Santos,

de Sousa,

Farias

et al. 2023

J. Chem. Educ.

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Seeking to foster the learning process and encourage the active participation of undergraduate students, this work proposes a new methodology that involves integrating smartphones into the learning process under a simple and accessible approach to learning in Chemistry and Physics laboratories aiming at facilitating the learning of some chemical concepts, such as thermodynamics and chemical equilibrium. Using RGB model data collected from images captured by students’ smartphones, the ΔH°, ΔS°, and ΔG° values of a colorimetric reaction with cobalt complexes were obtained using the equilibrium constant (K eq) and the concentrations of two complex cobalt ions at varying temperatures. The values obtained from the experiments conducted by the students were in agreement with those reported in the literature at 95% confidence level. The main pedagogical objective of this experiment was to show that based on digital images obtained from a smartphone, one can understand basic physical-chemistry concepts, taught in undergraduate courses, through the application of a simple methodology based on a widely accessible, low-cost technological device, and obtain results similar to those of UV–vis spectrophotometry. The use of digital images led to better assimilation of the concepts of reflectance and absorbance. The students considered the experimental procedure to be positively surprising, since they could use their smartphones to carry out the experiment. This work also presents a step-by-step guide for the acquisition of thermodynamic data using digital images from a smartphone.

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An Experimental Determination of Thermodynamic Values

Cited by 2 publications

References 3 publications

Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid

Determination of Thermodynamic Values (∆S°, ∆H°, and ∆G°) from the Dissociation of a Weak Acid

Determination of Thermodynamic Parameters Using Digital Image-Based Method

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