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近几年来,在部分省市中考的试卷上,出现了已、未知量均是体积的计算题。由于同学们平时见的多是已、未知量是质量的计算题,而且对气体的有关性质知之甚少,因此在解此类题时常感到束手无策。要能顺利解答这类题目,同学们应在已有的计算技能基础上,还必须掌握这样两个知识点: (1)同一命题中的各种气体,一般存在于同一反应或同一容器中,如无特殊说明,这些气体的温度和压强就相等; (2)同温同压下各气体之间的分子个数比等于它们的体积比(此信息常在命题中给出)。
In recent years, on the examination papers of some provinces and cities, there have been computational problems in which the volumes of known and unknown volumes are all. Since most of the students usually see that the quantity of unknowns is a calculation problem of quality and that they know little about the nature of gases, they often feel helpless in solving such problems. To successfully solve such problems, students should master these two knowledge points on the basis of existing calculation skills: (1) The gases in the same proposition are generally present in the same reaction or in the same container. Unless otherwise specified, the temperature and pressure of these gases are equal; (2) The ratio of the number of molecules between the gases at the same temperature and pressure is equal to their volume ratio (this information is often given in the proposition).