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在初中化学某些计算中,若能找出题中的不变量,并加以合理利用,就会使计算过程简化,达到事半功倍之效。兹举数例,供参考。1 视溶剂为不变量 例1 将一小块纯锌投入到47克稀硫酸中,锌块完全反应后称得溶液的质量为53克。求原稀硫酸溶液中含有多少克水? 分析:原稀硫酸溶液中所含水的质量,一定与反应后生成的硫酸锌溶液中所含水的质量相等。故可将水的质量视为不变量。 解:设原稀硫酸溶液中含水的质量为x。则含H_2SO_4的质量为(47克-x),反应后溶液含ZnSO_4为(53克-x)。依
In some calculations of junior high school chemistry, if we can find the invariants in the questions and make reasonable use of them, it will simplify the calculation process and achieve a multiplier effect. Here are some examples for reference. 1 depending on the solvent as invariant Example 1 A small piece of pure zinc was added to 47 g of dilute sulfuric acid. The zinc mass was completely reacted and the mass of the solution was determined to be 53 g. To find out how many grams of water are in the original dilute sulfuric acid solution? Analysis: The quality of the water contained in the original dilute sulfuric acid solution must be equal to the quality of the water contained in the zinc sulfate solution produced after the reaction. Therefore, the quality of water can be regarded as invariable. Solution: Set the mass of water in the original dilute sulfuric acid solution to x. The mass of H_2SO_4 was (47 g -x), and the solution containing ZnSO_4 was (53 g -x). according to