Acid-base Titration Research Articles

Combining with acid-base titration, HPLC, ATR-FTIR and chemometrics to study the effects of sulfur fumigation on medicinal and edible starchy samples

Combining with acid-base titration, HPLC, ATR-FTIR and chemometrics to study the effects of sulfur fumigation on medicinal and edible starchy samples

Implementation of the Afl Guided Inquiry Model to Optimize Learning Outcomes in Acid-Base Titration Material

Education in the era of globalization becomes a bridge that connects humans with the global environment in increasing the quality of human resources. This research describes the implementation, students' activities and responses, and the increase in learning outcomes before and after implementing an assessment for learning that is guided inquiry-oriented for Class XI Acid-Base Titration material. A quasi-experimental design with a nonequivalent control group design was used, while data collection instruments were questionnaires and tests. The scores of the guided inquiry model also obtained a score rating of 3-4, or very good, during the meetings. A comparison done through the right-hand t-test for the posttest 1 and posttest 2 analysis yielded a 0.000 p-value reflecting a significant enhancement statistically in the learning outcomes of students, at p < 0.05. Activities by the students were well conducted; the reception of the model was good, as shown by the average percentages, which ranged from 91.42% to 100%, falling within the "very good" range of acceptability.

Synthesis of furan-2-ones and spiro[furan-2,3ʹ-indoline] derivatives using polyether sulfone sulfamic acid catalysis

Polyether sulfone sulfamic acid (PES-NHSO3H) was prepared by simple sulfonation of a modified polyether sulfone. The number of acidic sites (SO3H) was determined to be 4.23 mmol H+/g by acid-base titration and 4.29 mmol H+/g by barium sulfate test. PES-NHSO3H was used as an efficient acidic catalytic system for the preparation of functionalized furan-2-ones and 2ʹ,5-dioxo-5 H-spiro[furan-2,3 ʹ -indoline]-3-carboxylate derivatives via the three-component reaction of anilines, aldehydes/1-ethylindoline-2,3-dione, and diethyl acetylene dicarboxylate in high yields (85–97%). The effect of polar and non-polar solvents on the productivity of the reaction was investigated. The catalyst was recovered 11 times without losses in catalytic potential.

A Staged Framework for Computer Vision Education: Integrating AI, Data Science, and Computational Thinking

Computer vision education is increasingly important in modern technology curricula; yet, it often lacks a systematic approach integrating both theoretical concepts and practical applications. This study proposes a staged framework for computer vision education designed to progressively build learners’ competencies across four levels. This study proposes a four-staged framework for computer vision education, progressively introducing concepts from basic image recognition to advanced video analysis. Validity assessments were conducted twice with 25 experts in the field of AI education and curricula. The results indicated high validity of the staged framework. Additionally, a pilot program, applying computer vision to acid–base titration activities, was implemented with 40 upper secondary school students to evaluate the effectiveness of the staged framework. The pilot program showed significant improvements in students’ understanding and interest in both computer vision and scientific inquiry. This research contributes to the AI educational field by offering a structured, adaptable approach to computer vision education, integrating AI, data science, and computational thinking. It provides educators with a structured guide for implementing progressive, hands-on learning experiences in computer vision, while also highlighting areas for future research and improvement in educational methodologies.

What Do Chemistry Teachers Say About Scientific Creativity and the Development of Rosella Flower Extract Indicators as a Learning Medium for Acid-Base Titration?

The rapid development of industry 4.0 makes scientific creativity an important skill for every individual to be able to adapt and develop. Therefore, in the learning process, it is necessary to provide for the development of students' scientific creativity both as a professional skill and as a general life competency. This research aims to describe teachers' perceptions of learning acid-base titration using natural indicators from Rosella Flower extract to increase students' scientific creativity. The research method used was a survey method by distributing questionnaires to 21 high school chemistry teachers throughout Bandar Lampung City. The results of the research show that 100% of teachers have never developed an acid-base titration indicator from Rosella flower extract, and trained students' scientific creativity by providing a real problem. Based on these findings, it can be concluded that it is necessary to develop natural indicators from Rosella Flower extract as a learning medium for acid-base titration to increase students' scientific creativity.

Water-Based Polyurethane Dispersions: A Detailed Analysis of the Particle Charge Using Soft and Hard Particle Model.

Water-based polyurethane dispersions (PUDs) show a characteristic dependency of the electrophoretic mobility on the electrolyte concentration, which can be investigated by hard and soft particle models. For this purpose, additional information can be obtained by determining particle charges and electrostatic potentials. PUDs with different contents of an intrinsic ionic stabilizer and various polyol components were synthesized according to the acetone process. The particle charge was characterized by potentiometric acid-base titration, and the data of the titration curve were fitted assuming multiple functional groups with adaptable acid strengths. To investigate the electrostatic potentials, electrophoretic mobilities were measured as a function of electrolyte concentration and analyzed by soft and hard particle theory. Acid-base titration experiments indicated that not all detected ionic groups are located on the surface but are partly arranged inside the polymer particle, as evidenced by a significant decrease of the corresponding effective dissociation constant. The evaluation of the titration data and the electrokinetic experiments showed that the soft particle model of Ohshima is not suitable to reflect the actual particle charge. In contrast, the hard particle model can describe the measured electrophoretic mobility of the dispersions very well if the relaxation effect is taken into account. The dependency of the corresponding zeta potentials on the electrolyte concentration can be excellently modeled assuming a constant surface potential ψ0 and distance of the shear plane xs. Reasonable results are obtained for both parameters with only minor differences between the PUD series. Nonetheless, the electrokinetic surface charge densities calculated with respect to the surface potential are lower than expected from the titration results. Although our results indicate a more complex charge distribution in a peripheral layer, the hard particle model currently shows the best description of the electrokinetic behavior of the PUDs.

Study on Antioxidant Activity of Purple Sweet Potato (Ipomoea Batatas) Juice Fermented with Lactobacillus plantarum B1765

Purple sweet potatoes are a source of anthocyanins, which are antioxidants. However, the anthocyanin compounds in purple sweet potatoes are naturally bound in glycosidic form, so their potential as antioxidants is still limited. Fermentation is one method that can be used to degrade glycosidic bonds to liberate free phenolics so that it can increase the antioxidant potential of purple sweet potato. This research aims to study the growth of lactic acid bacteria (LAB), pH, total titratable acid (TAT), phenolic content, anthocyanin content, and antioxidant activity of sweet potato juice (Ipomoea batatas) fermented with Lactobacillus plantarum B1765 starter culture for 0.2, 4,6,8,10,12 and 14 hours. Total LAB was measured using the Total Plate Count (TPC) method, pH was measured using a pH meter, TAT was measured using acid-base titration, total phenolic content (TPC) was measured using the Folline-Ciocalteu method, anthocyanin content used the differential pH method and antioxidant activity was measured using the radical scavenging method 2, 2-diphenyl-1-picrylhydrazyl (DPPH) which is expressed in IC50 values. The results showed that fermentation time affected (p<0.05) total LAB, pH, TAT, phenols, anthocyanin levels, and antioxidant activity in purple sweet potato juice. Total BAL increased to reach an optimum of 2.6 x 108 CFU/mL within 6 hours. However, until the end of fermentation for 14 hours, there was still a decrease in pH to 3.73, an increase in TAT reaching 0.426%, an increase in total phenolics up to 324.21 mg GAE/g, a reduction in anthocyanin levels (13.68 mg/L) and an increase in antioxidant activity with an IC50 of 47 .05 ppm which is classified as very strong. This product meets the Indonesian National Standards for fermented drinks and can potentially be a source of antioxidants.

Effect of Red Guava (Psidium guajava L.) Juice Concentration on Product Quality and Antioxidant Activity of Red Guava Synbiotic Yoghurt

Red guava juice has very strong antioxidant activity and has the potential to be processed into synbiotic functional beverage products that have health benefits. This study examined the effect of red guava juice concentration on product quality and antioxidant activity of red guava synbiotic yoghurt. Product quality tested included microbiological quality (total LAB) and chemical quality (pH value and Total Tritable Acid (TTA )value). The concentrations of red guava juice used were 0%, 10%, 20%, 30%, and 40%. Fermentation was carried out for 6 hours at 37⁰C by Lactic Acid Bacteria (LAB) from powdered mixed culture. Then organoleptic testing using the hedonic test, total LAB testing using the Total Plate Count (TPC) method, pH value testing using a pH meter, TTA value testing using the acid-base titration method, and antioxidant activity testing using the DPPH (2,2-diphenyl-1-picrylhydrazil) method. Test data were analyzed using SPSS software to determine the effect of red guava juice concentration on test results. The concentration of red guava juice in red guava synbiotic yoghurt affects the pH value, TTA value, and IC50 value as the result of antioxidant activity testing. Red guava juice concentration did not affect total LAB testing. Organoleptic assessment of red guava symbiotic yoghurt is in the range of like to like very much. The best formulation was red guava synbiotic yoghurt with 30% red guava juice concentration, which had strong antioxidant activity with an IC50 value of 59.637 ppm, pH value of 3.94, TTA value of 1.98%, and total LAB as much as 1.81x10⁸ colonies/g, so it has met the quality requirements of yoghurt according to Indonesian National Standard SNI 2981: 2009.

Effectiveness of Problem-Based Learning to Improve Critical Thinking Ability of Chemistry Students on Acid-Base Material

This study aims to determine the improvement of critical thinking skills of chemistry students through a problem-based learning (PBL) learning model on acid-base titration material. The method used is analytical descriptive research based on categorizing critical thinking skills with the research subject of chemistry education students in a regular class in 2022, consisting of 35 students. Data collection of critical thinking skills using essay tests reveals critical thinking skills in interpretation, analysis, inference, deduction, and evaluation. Research data were obtained from pretest and post-test results. The results showed the lowest N-gain value on the interpretation indicator and the highest on the deduction indicator, with an average N-gain value of 0.59 in the moderate category. This shows increased critical thinking skills after being treated using the PBL learning model.

Base-free trifluoroacetylation: From methyl glucopyranoside to cellulose nanofibers

Trifluoroacetic anhydride (TFAA) reacts smoothly with low molecular weight carbohydrates and cellulose nanofibers (CNFs) under base-free conditions. Methyl α- and β-d-glucopyranoside were used as model compounds to optimize reaction conditions, which were then applied to lyophilized CNFs for surface modification. ATR-IR spectroscopy and powder X-ray diffraction were employed to characterize the modified CNFs. Trifluoroacetylation for 4 h yields a degree of substitution (DS) of 0.4 acyl groups per anhydroglucose unit while maintaining a crystallinity index near 50 %. DS values were quantified by gravimetry, acid–base titration after saponification, and a novel approach utilizing solution 19F NMR spectroscopy which offers greater accuracy than the other techniques. This study presents an efficient, base-free method for derivatizing carbohydrates as well as surface functionalization of CNFs with trifluoroacetyl groups, potentially expanding their application in fiber-reinforced thermoplastic composites.

Probing Defects in Covalent Organic Frameworks.

Defects in covalent organic frameworks (COFs) play a pivotal role in determining their properties and performance, significantly influencing interactions with adsorbates, guest molecules, and substrates as well as affecting charge carrier dynamics and light absorption characteristics. The present review focuses on the diverse array of techniques employed for characterizing and quantifying defects in COFs, addressing a critical need in the field of materials science. As will be discussed in this review, there are basically two types of defects referring either to missing organic moieties leaving free binding groups in the material or structural imperfections resulting in lower crystallinity, grain boundary defects, and incomplete stacking. The review summarizes an in-depth analysis of state-of-the-art characterization techniques, elucidating their specific strengths and limitations for each defect type. Key techniques examined in this review include powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), scanning transmission electron microscopy (STEM), scanning tunneling microscope (STM), high resolution transmission electron microcoe (HRTEM), gas adsorption, acid-base titration, advanced electron microscopy methods, and computational calculations. We critically assess the capability of each technique to provide qualitative and quantitative information about COF defects, offering insights into their complementary nature and potential for synergistic use. The last section summarizes the main concepts of the review and provides perspectives for future development to overcome the existing challenges.

Concentration Scales and Solvation Thermodynamics: Some Theoretical and Experimental Observations Regarding Spontaneity and the Partition Ratio.

The solvation thermodynamics (ST) formalism proposed by A. Ben-Naim is a mathematically rigorous and physically grounded theory for describing properties related to solvation. It considers the solvation process as the transfer of a molecule ("solute") from a fixed position in the ideal gas phase to a fixed position within the solution. Thus, it removes any contribution to the solvation process that is not related to the interactions between this molecule and its environment in the solution. Because ST is based on statistical thermodynamics, the natural variable is number density, which leads to the amount (or "molar") concentration scale. However, this choice of concentration scale is not unique in classical thermodynamics and the solvation properties can be different for commonly used concentration scales. We proposed and performed experiments with diethylamine in a water/hexadecane heterogeneous mixture to confront the predictions of the ST, based on the amount (or "molar") concentration scale, and the Fowler-Guggenheim formalism, based on the mole fraction scale. By means of simple acid-base titration and 1H NMR measurements, it was established that the predictions of differences in the solvation Gibbs energy and the partition ratio (or "partition coefficient") of diethylamine between water and hexadecane are consistent with the ST formalism. Additionally, with current literature data, we have shown additional experimental support for the ST. However, due to the arbitrariness of the relative amount of solvents in the partition ratio, the choice of a single concentration scale within the classical thermodynamics is still not possible.

Analysis of the Thermal Aging Kinetics of Tallow, Chicken Oil, Lard, and Sheep Oil.

Understanding the thermal aging kinetics of animal oils is of vital importance in the storage and applications of animal oils. In this work, we use four different techniques, including UV-Vis spectrometry, viscometry, impedance spectroscopy, and acid-base titration, to study the thermal aging kinetics of tallow, chicken oil, lard, and sheep oil in the temperature range from 120 °C to 180 °C. The evolutions of the UV-Vis absorbance, dynamic viscosity, electric impedance, and acid titration are discussed with the defect kinetics. The evolutions of the color centers, defects for dynamic viscosity, and electric dipoles follow second-order, first-order, and zero-order kinetics, respectively. The temperature dependence of rate constants for the evolutions of the UV-Vis absorbance, dynamic viscosity, electric impedance, and acid titration satisfies the Arrhenius equation with the same activation energy for individual animal oils. The activation energies are ~43.1, ~23.8, ~39.1, and ~37.5 kJ/mol for tallow, chicken oil, lard, and sheep oil, respectively. The thermal aging kinetics of the animal oils are attributed to the oxidation of triglycerides.

Trace metal interaction with thermophilic phototrophic anaerobic bacterium Chloroflexus aurantiacus

Towards improving the knowledge of possible paleo-microorganisms interaction with trace metals (micro-nutrients and toxicants), we studied adsorption of Mn, Zn, Sr, Cd, and Pb onto modern Chloroflexus aurantiacus, thermophilic anoxygenic phototrophic bacterium which could be highly abundant in the Precambiran aquatic environments. Acid-base surface titrations allowed quantifying the number of proton-active surface groups, whereas non-electrostatic linear programming method (LPM) was used to assess the surface site concentrations and adsorption reaction constants between divalent cations (Zn, Mb, Sr, Cd, Pb) and bacterial surface, based on results of pH-dependent adsorption edge and constant-pH ‘langmuirian’ adsorption experiments. The total proton/hydroxyl binding site number of Chl. aurantiacus surfaces was sizably lower than that of other phototrophic anaerobic bacteria studied previously using similar experimental and modeling approach. Divalent metals exhibited a decreasing order of adsorption affinity (Pb > Cd ≥ Zn ≥ Mn > Sr), which reflected the order of cation hydrolysis and was similar to adsorption order on other phototrophic bacteria. At the same time, adsorption of Zn increased with increasing of temperature, from 4 °C to 60 °C and was stronger under light compared to the darkness. This suggested some active metabolic control involved in this metal interaction with bacterial surfaces. Overall, Chl. aurantiacus exhibited trace metal adsorption parameters (site number and binding constants) which were lower compared to other anoxygenic phototrophic bacteria (Rhodopseudomonas palustris; Rhodobacter blasticus) and cyanobacteria. This may reflect different bioavailability of trace metals in the paleo-ocean, given that thermophilic Chl. aurantiacus are among the oldest phototrophs on the planet.

Solvent-Free Synthesis of HKUST-1 with Abundant Defect Sites and Its Catalytic Performance in the Esterification Reaction of Oleic Acid.

HKUST-1 has received increasing attention because of its potential applications in many fields, such as heterogeneous catalysis, sensors, gas storage, and separation. Herein, we report that HKUST-1 can be facilely prepared by heating a ground mixture of copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid in an autoclave at 80 °C for 10 h. The data from nitrogen sorption show that the obtained material, named HKUST-1-free, possesses a high BET specific surface area of 1671 m2/g and a pore volume of 0.8 cm3/g. The results from acid-base titration indicate that the number of defect sites in HKUST-1-free is more than that in HKUST-1-solvent prepared by the solvothermal method. As a heterogeneous catalyst, HKUST-1-free gave a high yield (91%) of methyl oleate in the esterification reaction of oleic acid with methanol at room temperature compared to HKUST-1-solvent (70%). Additionally, it is proven that HKUST-1-free is a heterogeneous catalyst and can be reused.

Efficient Phosphate Adsorption from Groundwater by Mn-FeOOHs

Manganese co-precipitated with goethite (Mn-FeOOH) is ubiquitous within (sub-)surface environments, which are considered one of the most important sinks for phosphorus pollution management. Accordingly, various mole ratios of Mn-FeOOHs are synthesized and characterized by XRD, FE-SEM, FTIR, BET, XPS, hysteresis loop, acid–base titration and zero potential. According to XRD and FESEM images, the substitution of Mn causes subtle alterations in the microstructure and crystal structure of goethite, and the morphology of Mn-FeOOHs is transformed from needle-shaped goethite to a short-rod-shaped rough surface with increasing Mn substitution. Based on the analysis of BET and acid–base titration, the substitution of Mn into goethite significantly improved the surface area, pore volume, surface properties and active sites of goethite, thereby establishing a theoretical basis for effective subsequent adsorption. Batch experiment results show that the removal rate of phosphate decreases with the increasing solution pH, indicating that acidic groundwater conditions are more conducive to the removal of phosphate. In addition, the adsorption of phosphate on Mn-FeOOHs is independent of ionic strength, indicating that the inner-sphere surface complexation predominated their adsorption behaviors. The isotherm experiment results showed that Mn-G15 exhibits the strongest adsorption capacity for phosphate at pH 5.5 and T = 318 K, with a maximum adsorption capacity of 87.18 mg/g. These findings highlighted the effect of Mn content on the fixation of phosphate onto Mn-FeOOHs from (sub-)surface environments in pollution management.

The Effect of Self-Regulated Learning Strategy on Student Learning Outcomes in Acid-Base Titration Material

The Effect of Self-Regulated Learning Strategy on Student Learning Outcomes in Acid-Base Titration Material

Study of preparation of Herbal indicator from selected flower parts for acid base titration: A Green Chemical Approach

Suffering from the rapid depletion of the natural resource, the current world scenario calls for the need of sustainable development so as to obtain ecofriendly environment. Flowers impart beauty to the nature, pleasure to the heart and attract insects for pollination by their diversified colour, fragrance, shape and size. The variation in colour of flowers is due to the presence of pigments present in the petals or bracts. One of these pigments is anthocyanin which is a natural plant pigment. These pigments impart different colours in acidic and basic medium. This change in colour forms the basis for using flower sap as indicator in acidimetry and alkalimetry. Synthetic indicators are good choice for acid base titration. But due to environmental pollution, less availability and high cost of synthetic indicator, the search for natural compounds as an acid base indicator started. Natural indicators are easy to prepare, are easily available and promising results are obtained when tested against standard synthetic indicators.

INFLUENCE OF KNOWLEDGE OF LABORATORY SKILLS ON STUDENTS' PERFORMANCE IN ACID-BASE TITRATION IN OREDO LGA, EDO STATE

This study examined the influence of knowledge of laboratory skills, sex, and school ownership on students’ performance in acid-base titration in Oredo local Government Area, Edo State. Based on these, four research questions were raised and three were hypothesized and tested at 0.05 alpha level of significance. A causal-comparative (expo-facto) research design was adopted as the research design for the study. The population for the study consists of all Senior Secondary School II chemistry students in public and private secondary schools in Oredo Local Government Area. A sample of three hundred and twenty-six (326) chemistry students were selected for this study through purposive random sampling techniques. An instrument titled ‘Laboratory Skills and Titration Performance Test in Acid-base Titration (LSPTT)’ was used to collect data from the students in the study. The questionnaire had a reliability coefficient of 0.831 using Cronbach Alpha Statistics while the performance test had a reliability coefficient of 0.760 using Kuder Richardson (KR-20), hence the instrument was deemed reliable. The data collected from the students were analyzed using, mean, standard deviation, and multiple regression. The results from the study showed that observation, reading, and safety skills were predominantly used. The result from the study also showed that laboratory skills contributed to and influenced the performance of the students in acid-based titration, whereas, sex and school ownership did not influence the performance of the students. Based on the findings in the study, it was recommended that the teaching of laboratory skills in practical Chemistry should be prioritized to enable the students to perform successfully in their practical examinations.

Sulfonated graphitic carbon catalyst derived from coffee waste: A sustainable valorization approach for highly efficient production of 5-hydroxymethylfurfural (5-HMF) from fructose

According to recent research, a sulfonated 2D graphitic carbon catalyst for the dehydration of fructose to the platform chemical 5-Hydroxymethylfurfural (5-HMF) can be made from used ground coffee. By carbonizing and activating at different temperatures, sulfonated graphitic carbon (SC) catalysts with varied chemical compositions and textural characteristics were obtained. The physical and chemical characteristics of the SC catalysts were assessed using XRD, Raman, SEM-EDX, HR-TEM, BET analysis, and XPS. Due to its microporous structure, SC-900 exhibited a high specific area and demonstrated selective and efficient production of 5-HMF from fructose. All in all, the surface acidity of catalysts was measured by NH3-TPD, and acid-base titration methods. The SC-900 catalyst, designed through carbonization at 900 ℃, achieved a fructose conversion rate of 100 % and a 5-HMF yield of 97.91 % without generating any by-products. This indicates the catalyst essentially produces 5-HMF under the specified optimal conditions (140 ℃, 90 min) observed in this study. To determine the origins of the highly efficient and highly selective conversion of fructose to 5-HMF, the performance of the SC catalysts was systematically investigated vi-a-vis their physical and chemical properties. The development of microporous SC catalysts and their application as catalysts not only enhances the value of waste coffee but also provides an environmentally friendly approach for converting carbohydrates into 5-HMF.