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在《电解质溶液》一章的教学中,读者往往在溶液的酸碱性、水的离子积、盐的水解规律以及酸式盐水溶液酸碱性判据问题上迷惑不解,下面就他们的疑点进行逐一分析: 一、任何物质的水溶液中都含有H~+和OH~-离子吗? 读者往往误以为,酸式溶液里只含有H~+,碱性溶液里只含有OH~-,只有水才同时含有H~+和OH~-,这是一种片面观点。 诚然,纯水里的确存在等量的H~+和OH~-。如25℃时,[H~+]=[OH~-]=1.0X10~(-7)M。 倘若向纯水里加入0.1M的盐酸使H~+离子浓度为0.1M,它比纯水里所含[H~+]=1X10~(-7)M大得多,并对水的电离产生抑制(同离子效应),致使水所电离出的H~+大为减少,以至可忽略,所以溶液中的氢离子浓度可视为0.1M。
In the teaching of “Electrolyte Solution” chapter, the reader is always puzzled by the problems of acid-base solution, water ion product, salt hydrolysis law and acid-base acidity criterion of acid brine solution. One by one analysis: First, any substance in aqueous solution contains H ~ + and OH ~ - ion? Readers often mistakenly believe that acid solution contains only H ~ +, alkaline solution contains only OH ~ -, only water Only at the same time contains H ~ + and OH ~ - This is a one-sided view. Admittedly, there is indeed an equivalent amount of H ~ + and OH ~ - in pure water. Such as 25 ° C, [H ~ +] = [OH ~ -] = 1.0X10 ~ (-7) M. If 0.1M hydrochloric acid is added to pure water to make the concentration of H + ion 0.1M, it is much larger than [H ~ +] = 1X10 ~ (-7) M contained in pure water and the ionization to water Inhibition (with the ion effect), resulting in H ~ ionized water is greatly reduced, and even negligible, so the concentration of hydrogen ions in the solution can be considered as 0.1M.