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强碱与弱酸形成的盐,既有正盐,又有酸式盐。其正盐溶于水时,由于盐电离出的弱酸根离子和水中的H~+结合形成弱酸(或酸式酸根阴离子),破坏了水的电离平衡,改变了溶液中H~+和OH~-的相对浓度,致使[H~+]<[OH~-],溶液呈现碱性。而强碱与多元弱酸所形成的酸式盐其水溶液是否也呈现碱性反应呢?答曰:不一定。其可能呈碱性,也可能呈现酸性。我们先以NaHCO_3为例,来讨论强碱弱酸的酸式盐水溶液的酸碱性,从而找出这类盐溶液酸碱性判断的一般规律及其pH值的近似计算公式。
Salts formed by strong bases and weak acids include both normal salts and acid salts. When the salt is dissolved in water, the weak acid ion ionized by the salt and the H~+ in the water combine to form a weak acid (or acid anion), destroying the ionization balance of the water, and changing the H~+ and OH~ in the solution. - Relative concentration, resulting in [H~+]<[OH~-], alkaline solution. However, does the acidic solution formed by a strong base and a plurality of weak acids also exhibit an alkaline reaction in an aqueous solution? It may be alkaline or it may be acidic. We first use NaHCO 3 as an example to discuss the acidity and alkalinity of the acidic brine solution of strong bases and weak acids, so as to find out the general laws of acidity and alkalinity judgment of such salt solutions and the approximate calculation formula of pH value.