Question

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   

(14分)某中学课外兴趣小组用惰性电极电解饱和食盐水（含少量Ca²⁺、Mg²⁺)作系列探究，装置如下图所示：

(1)电解时，甲同学发现电极a附近溶液出现浑浊,请用离子方程式表示原因____________

(2)一段时间后，你认为C中溶液可能出现的现象是______，请用离子方程式表示原因________________________

(3) 实验结束后，乙同学将A中的物质冷却后加入到H₂S溶液中发现有气泡出现，但加人到稀盐酸中却没有任何现象。请用化学方程式和简要的文字解释原因____________

(4) 随着反应的进行，兴趣小组的同学们都特别注意到D中溶液红色逐渐褪去。他们对溶液红色褪去主要原因提出了如下假设，请你完成假设二。

假设一:B中逸出气体与水反应生成的物质有强氧化性，使红色逐渐褪去；

假设二 ：__________________________________________。

(5) 请你设计实验验证上述假设一，写出实验步骤及结论___________________________________________________________________________

 

Answer 1

（共 14 分）

（1）2H⁺ + 2e^-=H₂↑,Mg²⁺ +2OH^-=Mg（OH）₂↓（2分）

（2）有淡黄色沉淀（2分）   Cl₂+S^2-=2Cl^-+S↓（2分）

（3）Ag置换H₂S的反应式为：2Ag+H₂S=Ag₂S+H₂,表明Ag₂S的溶解度比AgCl小很多（3分）

（4）可能是H⁺中和了OH^-造成褪色（2分）

（5）1.取少量D中褪色后的溶液于试管中

2.滴加1-2滴酚酞溶液,如果又显红色,则假设一正确（3分）

解析:略