China 
Africa 
Explore chapters and articles related to this topic
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−
General Chemistry
Published in Steven L. Hoenig, Basic Chemical Concepts and Tables, 2019
Chemical equilibrium is reached in a chemical reaction when the rate of the forward reaction is equal to the rate of the reverse reaction, and the concentrations of the reactants and products do not change over time (Figure 1.16). The reaction can be represented as follows:
Role of Bacteria on Pyrite Oxidation
Published in V. P. (Bill) Evangelou, and Its Control, 2018
When the rate of the forward reaction equals the rate of the backward reaction a chemical equilibrium state is met, and Keq=(k1/k−1)=[FII:S1-S2:B][Aa+][FII:S1-S2:A][Bb+]
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.
Fuel gas production from asphaltene and recycled polyethylene
Published in Petroleum Science and Technology, 2020
Jia-Ming Zhu, Jia-Bao Liu, Muhammad Kamran Siddiqui, Waqas Nazeer, Yun Liu
Figure 1 show the effect of temperature on H2/CO in the process of gasification of asphaltene (Moreno-Arciniegas et al. 2009) and polyethylene (He et al. 2009; Erkiaga et al. 2013). According to the figure, increasing temperature increases H2/CO, the reason for which will be elaborated as follows. According to Le Chatelier’s principle, increasing temperature in endothermic processes, like gasification, causes chemical equilibrium to move toward products. This means that in the endothermic reactions of water-gas and steam reforming, increasing temperature will increase H2 production. On the other hand, increasing temperature will also slightly increase CO, since tar cracking reactions in high temperatures progress towards lighter carbons and a mixture of CO and H2. Although tar is a mixture rich in heavy hydrocarbons, minimizing the amount of tar obtained from thermochemical processes has been the goal, since this compound can block pipes and cause operational problems in end-use engines. There are various ways to reduce tar, the most important of which is using active catalysts. Another method is using condensers, which is of course more expensive than the previous method.
Simulation analysis of steam gasification of petroleum coke with CaO
Published in Petroleum Science and Technology, 2018
Wei Tian, Fusheng Yan, Rongzhen Liang
Because an increase in temperature leads to a shift of the chemical equilibrium to the endothermic direction. Since the chemical reactions Eq. (5) and (6) are endothermic reactions, the chemical equilibrium shifts in the forward direction, resulting in a sharp decrease in the volume fraction of CH4. At the same time, chemical reaction Eq. (1) is also endothermic reaction, and chemical equilibrium moves forward. A series of chemical equations are coupled to increase the volume fraction of H2 and CO. The chemical reaction Eq. (7) is an exothermic reaction and therefore moves in the opposite direction, resulting in a decrease in the volume fraction of CO2.