Writing as a teaching learning technique: an example in chemistry (molar solution)

Techniques are needed to train students in "writing to learn"., whose main goal is to "learn to write". This work aims to exemplify how writing can be a teaching learning technique in an example in Chemistry to develop a correct understanding of the preparation of molar solutions in the laboratory. It is essential that this is carried out in the classroom in a way that develops the reflective, analytical and cognitive skills of students. All this within an environment with safety measures at work.

Effect of silanized sisal fiber on thermo-mechanical properties of reinforced epoxy composites

An effective method was adopted to improve the thermo-mechanical properties of the epoxy composite by functionalization of the sisal fiber. Initially, a neat sisal fiber was acetylated with molar solution of acidic mixture (0.5:1 of HNO3:H2SO4) that removed the content of lignin and hemicellulose and increased the crystallinity of the sisal fiber. The acetylated sisal ( a-sisal) fiber was further treated with 3-aminpropyltriethoxy silane to graft the silanol moieties on sisal fiber. The functionalization of the sisal fiber with 3-aminpropyltriethoxy silane exhibits the strong interaction with epoxy, resulting in homogenous dispersion of the sisal fiber in epoxy. The composite possesses great enhancement in thermal and mechanical properties. The tensile strength in functionalized sisal epoxy composite ( CP-f-Sisal) was significantly enhanced up to 23% in comparison to non-functionalized sisal epoxy composite ( CP-n-Sisal) by adding 15 wt.% of the sisal fiber. In addition, the functionalized sisal epoxy composite ( CP-f-sisal) shows better thermal stability as compared to non-functionalized sisal epoxy composite ( CP-n-sisal). Similar results are attributed by investigating the kinetics of thermal stability parameters that include activation energy and integral procedure decomposition temperature.

Synthesis and Modification of Zeolite ZSM-5 Catalyst with Solutions of Calcium Carbonate (CaCO3) and Sodium Carbonate (Na2CO3) for Methanol to Gasoline Conversion

In this article, the ZSM-5 catalyst was used as the base catalyst and its structure was modified for conducting Methanol to Gasoline reactions. ZSM-5 catalyst reacts to the solutions with diverse concentrations of calcium carbonate (CaCO3) and sodium carbonate (Na2CO3), and consequently, some changes were applied to its internal structure. Thus, Methanol to Gasoline (MTG) process was carried out under pressure of 1 atm, the temperature of 400°C, and specific surface area of 300 m2g-1 on synthetic zeolite ZSM-5 catalyst by a fixed-bed reactor. Structure and morphology of the synthesized catalyst were investigated by XRD, FT-IR, SEM, XRF and BET analyses. The effect of CaCO3 and Na2CO3 solutions used for catalyst modification on the distribution of hydrocarbon products were studied and compared to ZSM-5 catalyst. The result of catalyst activity evaluation tests shows that the modified catalyst with a 0.1 molar solution of CaCO3 and Na2CO3 provides the highest selectivity and efficiency compared to the hydrocarbons in boiling point range of C6+ gasoline.

Linear Potentiodynamic Characterization of ECAPed Biocompatible AZ91 Magnesium Alloy

Mechanical properties and corrosion resistance of Mg alloys basically depend on their chemical composition. Both the mentioned can be influenced by mechanical or heat treatment. In this work was studied the effect of production technology and resulting microstructure on the corrosion resistance of AZ91 alloy. Corrosion resistance of the alloy (AZ91) was analyzed for material after casting and after treatment by ECAP. Result of ECAP treatment is fine grained microstructure of AZ91 alloy and uniform distributed of present intermetallic phases. Corrosion resistance of the experimental material was analyzed in 0.1 molar solution of NaCl through potentiodynamic tests. The ultra-fine grained microstructure after ECAP results in movement of thermodynamic curves to more positive values of corrosion potential (Ecorr). From thermodynamic point of view, this means, that AZ91 alloy after ECAP has slightly higher corrosion resistance, as AZ91 alloy after casting; however the improvement of corrosion resistance is only minor due to the high reactivity of the magnesium in the corrosion environment.

Crystal structure of tetrabutylammonium bromide–1,2-diiodo-3,4,5,6-tetrafluorobenzene–dichloromethane (2/2/1)

The crystallization of a 1:1 molar solution of 1,2-diiodo-3,4,5,6-tetrafluorobenzene (o-DITFB) and tetrabutylammonium bromide (n-Bu4NBr) from dichloromethane yielded pure white crystals of a halogen-bonded compound, C16H36N+·Br−·C6F4I2·0.5CH2Cl2or [(n-Bu4NBr)(o-DITFB)]·0.5CH2Cl2. The compound may be described as a quaternary system and may be classified as a salt–cocrystal solvate. The asymmetric unit contains one molecule of solvent, twoo-DITFB molecules, two cations (n-Bu4N+) and two crystallographically distinct bromide ions [θI...Br-...I= 144.18 (1) and 135.35 (1)°]. The bromide ion is a bidentate halogen-bond acceptor which interacts with two covalently bonded iodines (i.e.halogen-bond donors), resulting in a one-dimensional polymeric zigzag chain network approximately along theaaxis. The observed short contacts and angles are characteristic of the non-covalent interaction [dC—I...Br= 3.1593 (4)–3.2590 (5) Å; θC—I...Br= 174.89 (7) and 178.16 (7)°]. It is noted that iodine acts as both a halogen-bond donor and a weak CH hydrogen-bond acceptor, while the bromide ions act as acceptors for weak CH hydrogen bonds and halogen bonds.

Synthesis, Characterization, Modeling and Anti-Bacterial Properties of Peanut-Shaped ZnO Nano-Bunches

Since few decades, the fabrications of metal oxide nanoparticles (MO-Nps) as well as their uses in various segments have been increased manifolds. An easy effort to produce an important category of MO-Nps as Zinc oxide nanoparticles (ZnO-Nps), with the assistance of mechano-solution method at various low temperatures, introducing Zinc acetate dihydrate and Sodium hydroxide into the molar solution of C19H42NBr complex (Cetrimonium bromide, CTAB) for much less than an hour was projected. The impact of this method performed at two different ranges of process temperatures was studied and the magnitude of the ZnO-Nps (like particle size, morphology and L/D dimensions) has been reported. On the top of this, the morphological study of these Nps has been presented. The characterization of the synthesized Nps was carried out with the help of SEM with EDS, XRD, UV-Vis spectroscopy. The scanning electron microscopy has revealed the synthesis of peanut-shaped ZnO nanobunches (NBs) at two different ranges of temperature. An overall viable growth of the solitary nanoparticles constituting of ZnO-NBs has also been put forth. Hence, the effect of temperature on C19H42NBr complex (stabilizer) has been reported. In addition, a postulated model depicting the relationship of the temperature effect on the process parameters of ZnO-NBs has also been floated. The Gram +ve bacteria, Bacillus subtilis is a rod shaped bacteria which is commonly known as normal gut commensal in humans. Due to the emergence of anti-biotic resistant drugs, alternate medications are under primary considerations. A noteworthy experimentation was concerned with anti-bacterial activity of therapeutically viable Gram +ve bacteria, Bacillus subtilis and it was found that reported ZnO-NBs have become the promising entities for terminating the growth of these bacterias.

Tunable Liquid Dielectric Antenna

This paper presents on modified the dielectric properties of liquid with varying salinity that was based on monopole structure. Dielectric resonator antennas (DRAs) can be made with a wide range of materials and allow many excitation methods [2]. Pure water does not work at high frequency (> 1 GHz) but increase in the salinity of water modifies the dielectric properties of water. Here proposed antenna shows that when the salinity increases in form of molar solution, the antenna was tuned at different frequency with increases return loss.

Volumetric Analysis

Volumetric analysis is a chemical analytical procedure based on measurement of volumes of reaction in solutions. It uses titration to determine the concentration of a solution by carefully measuring the volume of one solution needed to react with another. In this process, a measured volume of a standard solution, the titrant, is added from a burette to the solution of unknown concentration. When the two substances are present in exact stoichiometric ratio, the reaction is said to have reached the equivalence or stoichiometric point. In order to determine when this occurs, another substance, the indicator, is also added to the reaction mixture. This is an organic dye which changes color when the reaction is complete. This color change is known as the end point; ideally, it will coincide with the equivalence point. For various reasons, there is usually some difference between the two, though if the indicator is carefully chosen, the difference will be negligible. A typical titration is based on a reaction of the general type aA+bB → products where A is the titrant, B the substance titrated, and a:b is the stoichiometric ratio between the two. Some indicators include Litmus, Methyl Orange, Methyl Red, Phenolphthalein, and Thymol Blue. Titration can be applied to any of the following chemical reactions: • Acid–base • Complexation • Oxidation–reduction • Precipitation Only acid–base and oxidation–reduction titration will be treated here, though the fundamental principles are the same in all cases. Acid–base titration involves measuring the volume of a solution of the acid (or base) that is required to completely react with a known volume of a solution of a base (or acid). The relative amounts of acid and base required to reach the equivalence point depend on their stoichiometric coefficients. It is therefore critical to have a balanced equation before attempting calculations based on acid–base reactions. Below we define some of the common terms associated with acid–base reactions. A molar solution is one that contains one mole of the substance per liter of solution. For example, a molar solution of sodium hydroxide contains 40 g (NaOH=40 g/mol) of the solute per liter of solution. As described in chapter 13, the concentration of a solution expressed in moles per liter of solution is known as the molarity of the solution.