核反应与化学反应
All the changes taking place in the environment are due to either chemical or nuclear reactions. What these mean, and how they differ from each other are discussed below.
Chemical Reaction
Chemical reaction is a process of converting a set of substances into another set of substances. The substances at the beginning of the reaction are known as reactants, and the substances after the reaction are known as products. When one or more reactants are converting into products, they may go through different modifications and energy changes. The chemical bonds in the reactants are breaking, and new bonds are forming to generate products, which are totally different from the reactants. This kind of chemical modification is known as chemical reactions. Chemical reactions are described using chemical equations. There are numerous variables controlling the reactions. Some of these factors are concentrations of the reactants, catalysts, temperature, solvent effects, pH, and sometimes the product concentrations etc. Mainly, by studying thermodynamics and kinetics, we can draw many conclusions about a reaction and control them. Thermodynamics is the study of transformations of energy. It is only concerned with the energetic and the position of the equilibrium in a reaction. It has nothing to say about how fast the equilibrium is reached. This question is in the domain of kinetics.
Reaction rate is simply the indication of the speed of the reaction. So it can be regarded as a parameter, which determines how fast or how slow is the reaction. Naturally, some reactions are very slow, so we cannot even see the reaction taking place unless we observe it for a very long time. For example, rock weathering by chemical processes is a slow reaction that takes place over the years. In contrast, reaction of a piece of potassium with water is very rapid; thus, producing a large amount of heat, and it is considered as a vigorous reaction. Consider the following reaction where reactants A and B are going into products C and D.
a A + b B→C C + D D
反应的速率可以用两种反应物或产物中的一种。
速率= -1/a×d [a]/dt = -1/b×d [b]/dt = 1/c×d [c]/dt = 1/d×d [d]/dt
Here, a, b, c and d are stoichiometric coefficients of the reactants and products. For the reactants, the rate equation is written with a minus sign, because the products are depleting as the reaction proceeds. However, as the products are increasing, they are given positive signs.
Nuclear Reaction
The nuclei of an atom or subatomic particles participate in nuclear reactions. Nuclear fission and nuclear fusion are the two major types of nuclear reactions. Nuclear reactions are mainly used to generate energy as it produces energy in much higher folds than chemical reactions. In a fission reaction, a large- unstable nucleus is split into smaller-stable nuclei and, in the process, energy is released. In a fusion reaction, two types of nuclei are combined together, releasing energy.
核反应和化学反应有什么区别？ •在化学反应中，原子，离子，分子或化合物充当反应物，而在核反应中，原子或亚原子颗粒的核参与。 • In chemical reactions, the changes occur in the atoms’ electrons. In nuclear reactions, changes mainly occur in atoms’ nucleus. • Energy involved in nuclear reactions is much higher than that of chemical reactions. • Rate of a chemical reaction depends on factors like pressure and temperature, but nuclear reactions do not depend on these factors, as chemical reactions do. |
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