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The Groundwater Geochemical System
Published in William J. Deutsch, Groundwater Geochemistry, 2020
Each chemical reaction has associated with it an equilibrium constant (K). The equilibrium constant is a numerical value that represents the ratio of the activities (effective concentrations) of the participants in the chemical reaction when that reaction has reached chemical equilibrium. At equilibrium, the ratio of the activities will not change and can be represented as a constant (K). For example, calcite dissolution in water can be represented by the following reaction: () CaCO3(s)→Ca2++CO32−
Chemical Equilibrium
Published in Franco Battaglia, Thomas F. George, Understanding Molecules, 2018
Franco Battaglia, Thomas F. George
We recall that the enthalpy increase of a system coincides with the heat absorbed at constant pressure (Section 9.9). Therefore, a chemical reaction is said to be exothermic or endothermic according to whether ΔH < 0 or ΔH > 0. From Eq. (11.16) we see that if the reaction with all components in the standard state is exothermic (i.e., ΔH0 < 0), then increasing the temperature entails a decreasing of the equilibrium constant, and the equilibrium moves toward the reactants. If, instead, the reaction is endothermic (i.e., ΔH0 > 0), then increasing the temperature entails an increasing of the equilibrium constant, and the equilibrium moves toward the products. In other words, an increase in temperature displaces the equilibrium in the direction along which the system absorbs heat, in agreement with Le Chatelier’s principle (Section 9.9.2).
Reactions Involving Gases
Published in David R. Gaskell, David E. Laughlin, Introduction to the Thermodynamics of Materials, 2017
Consider again the reaction Cl2 = 2Cl. Completion of this reaction causes a doubling of the number of moles present, and the effect of a change in pressure can again be obtained by the application of Le Chatelier’s principle. If the pressure exerted on a system at reaction equilibrium is increased, then the equilibrium shifts in that direction which tends to decrease the pressure exerted by the system; that is, it shifts in that direction which decreases the number of moles present. Thus, if the pressure exerted on the Cl–Cl2 system is increased, the equilibrium will shift toward the Cl2 side, as, thereby, the total number of moles present will be decreased to accommodate the increased pressure. Specifically, the effect of pressure on the reaction equilibrium expressed in terms of the number of moles present (or in terms of mole fractions) can be seen as follows:
A Methodological Approach to Select a Suitable Azodicarbonamide Based Airbag Gas Generant
Published in Combustion Science and Technology, 2023
Jeyabalaganesh G, Sivapirakasam S P, Sreejith Mohan, Aravind S.L, Harisivasri Phanindra K
The oxygen supply efficacy of the oxidizers, as well as the oxygen intake efficacy of the fuel, can be determined based on the chemical equilibrium principle. The chemical equilibrium occurs when the forward rate of reaction equals the backward rate of reaction, and both product and reactants are present in concentrations that do not change with time. The mass balance on either side of equation 1 can determine the oxygen supply efficacy of the oxidizers by calculating the quantity of oxidizer that decomposes to give 1 g of O2. Similarly, the oxygen intake efficacy of the fuel can be determined by the mass balance on either side of equation 2, which calculates the quantity of fuel that gets oxidized by 1 g of O2.
Separation of phosphoric acid and magnesium from wet process phosphoric acid by solvent extraction
Published in Canadian Metallurgical Quarterly, 2022
Baoqi Wang, Qinglie Zhou, Chuan Chen, Haifeng Liu, Lin Yang
The findings of the experiment indicate that under the situation of rising temperature (Figure 9). With an increase in temperature, the stripping efficiency of magnesium ions using ammonium sulfate solution as the stripping agent decreases. It shows that the stripping reaction is an exothermic process. An increase in temperature will shift the reaction equilibrium to the opposite direction. Thus, the stripping reaction is suppressed. As the temperature increases from 293.15 to 353.15 K, the stripping efficiency reduces by 9.1%. The degree of decrease is not significant. The lower the temperature, the worse the effect of phase separation after the reaction. For industrialisation, if the phase separation effect inadequate, the stripping liquid will be carried into the subsequent stripping stage, consequently compromising the overall water balance. Therefore, 333.15 K is chosen for the following trials with a single component.
Biodiesel production from non-edible crops using waste tyre heterogeneous acid catalyst
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Sakthi Saravanan Arumugamurthi, Periyasamy Sivanandi, Senthilkumar Kandasamy
During biodiesel conversion, the temperature plays an important effect. The esterification processes are naturally endothermic. As a result, as the temperature rises, the biodiesel conversion increases. Figure 8 depicts the influence of reaction temperature on biodiesel yield. Upon increasing the reaction temperature from 30°C to 60°C, biodiesel production rose as the reaction rate increased. As a result, an optimum temperature of 60°C produced an 82.1 wt% biodiesel output. The reason for this is that a temperature rise accelerates the forward reaction rate. According to Le Chatelier’s principle, when the temperature rises, the equilibrium changes to the right for endothermic processes. Methanol nearly approaches the boiling point at 60°C reaction temperature. Methanol bubbles up and quickly mixes with the oil phase. The biodiesel conversion was enhanced by the fast movement of the reactants caused by the formation of bubbles. Similar results were observed for the production of Nigerian palm kernel oil (Alamu, Waheed, and Jekayinfa 2009). An ensuing increment brought about a slight abatement in yield because of the appearance of reverse reaction along with a rise in gas phase methanol concentration at boiling point. Yet, reaching the highest biodiesel yield at a temperature far below the methanol’s boiling point is an intriguing result in terms of cost savings (Wang et al. 2019).