问题 填空题

(10分)向胶体中加入少量电解质或将两种带相反电荷的胶体混合,能使胶体粒子聚集长大,形成的颗粒较大的沉淀从分散剂里析出,这个过程叫做聚沉。在Fe(OH)3胶体中,逐滴加入HI稀溶液,会产生一系列变化:

(1)先出现红褐色沉淀,原因是                                                   

(2)随后沉淀溶解,溶液呈黄色,该反应的离子方程式为                             

(3)最后溶液颜色加深,原因是。此反应的离子方程式为                              

(4)用稀盐酸代替HI稀溶液,能出现上述哪些相同的现象(填序号)

                     

答案

(1)加入电解质后,使胶体聚沉

(2)Fe(OH)3+3H+Fe3++3H2O

(3)有I2生成2Fe3++2I-I2+2Fe2+

(4)(1)(2)

向Fe(OH)3胶体中加HI稀溶液,产生的一系列变化是:Fe(OH)3胶体在加入电解质后,先聚沉,然后Fe(OH)3+3H+Fe3++3H2O,最后Fe3+与I-发生氧化还原反应。用稀盐酸代替HI稀溶液,(1)(2)现象相同,但不可能出现(3)现象,因为Fe3+不能与Cl-发生氧化还原反应。

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                                                Four ways to have a good school-life

    Your schooldays should be some of the best and happiest days of your life. How can you get the most

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     ④                 

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there are also a lot of things to do. You may read a book, practise English or help Mother with housework.

     Follow our advice, and have a happy school-life!

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