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使酚酞溶液变红的一定是碱溶液吗
更新时间: 2020-10-28 00:00:00  

不是的。碱性的盐溶液,碱性有机物的溶液,强酸弱碱盐水解也会使酚酞试液变红。酚酞是一种有机弱酸,它在酸性溶液中,浓度较高时,形成无色分子。但随着溶液中H+浓度的减小,OH-浓度的增大,酚酞结构发生改变,并进一步电离成红色离子这个转变过程是一个可逆过程,如果溶液中H+浓度增加,上述平衡向反方向移动,酚酞又变成了无色分子。因此,酚酞在酸性溶液里呈无色,当溶液中H+浓度降低,浓度升高时呈红色。酚酞的变色范围是pH8.0~10.0。

关键词: 酚酞 溶液 一定

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