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【题目】某化学学习小组为了探究新制备的饱和氯水的组成和性质进行了科学实验:先观察了氯水的外观后,再用滴管将新制备的氯水逐滴滴入含有酚酞的红色NaOH溶液中,边滴加边振荡,并观察现象,结果溶液中的红色逐渐褪去,得到无色溶液。请回答:

(1)写出新制的氯水中含氯元素的物质的化学式_________________________。

(2)根据预测,实验中溶液红色褪去的原因可能有两种。请用简要的文字说明:

①__________________________________;

②__________________________________。

(3)为了探究溶液红色褪去的原因是上述原因中的①还是②,请叙述相应的实验方法、现象和结论。

____________________________________。

【答案】 (1)Cl2、HCl、HClO

(2)①HCl中和了NaOH溶液而使红色褪去

②HClO氧化了酚酞而使红色褪去

(3)取无色溶液少许于另一支洁净的试管中,加过量NaOH溶液,振荡,观察现象。若溶液又变为红色,则证明溶液红色褪去的原因是①而不是②;若溶液仍为无色,则证明溶液红色褪去的原因是②而不是①

【解析】 氯水中含氯元素的物质有Cl2、HClO、HCl。溶液的红色是酚酞与氢氧化钠相互作用的结果,若是氯水中的酸中和了氢氧化钠而使红色褪去,则再加入氢氧化钠溶液后还会变红;若是氯水中的HClO氧化了酚酞而使红色褪去,则溶液中就不存在酚酞了,即使加入过量NaOH溶液也不会再变红。

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