It is Saturday afternoon. Liu Tao and his friend David are taking a walk in the park. There are many public signs in it. They mean different things. Liu Tao knows a lot of things about them. Suddenly, they see a short man walking on the grass. Liu Tao points to the sign on the grass and says to him, "Sir, look at the sign! You can't walk on the grass. "The man smiles and says, "You are right, young man. But I'm the park keeper. I'm looking after the grass. "

我国许多大河滚滚东流，既沟通了东西交通，又产生了巨大水能，这是因为（     ）

某小组同学用如图装置进行实验研究（a、b、c表示止水夹）．请评价或完善其方案：

（1）将装置A、C、E相连接，用MnO₂和浓盐酸制取氯气，请回答：

①A中反应的离子方程式：____ 

②E中氢氧化钠溶液的作用____ ．

在C中加入适量的水可制得氯水．将所得氯水分成两份进行实验，其操作、现象和结论如表：

③．实验Ⅰ推出的相应结论是否合理？____ ，若不合理，请说明理由（若合理，无需填写）____ ．

④．实验Ⅱ推出相应的结论是否合理？____ ，若不合理，请说明理由（若合理，无需填写）____ ．

（2）将B、D、E相连，在B中装浓硝酸和铜片，可制得NO₂并进行有关实验．

①B中反应的化学方程式____ ．

②先若关闭c，当丁中充满红棕色的NO₂时，再关闭止水夹a、b，微热试管丁，丁中可观察到的实验现象____ ．