为验证卤素单质氧化性的相对强弱，某小组用右图所示装置进行试验(夹持仪器已略去，气密性已检验)。试验过程：

I．打开弹簧夹，打开活塞a，滴加浓盐酸。
II．当B和C中的溶液都变为黄色时，夹紧弹簧夹。
III．当B中溶液由黄色变为棕色时，关闭活塞a。
IV．……
试回答下列问题：
（1）A中产生                                                                                                        色气体，其结构式是                 。
（2）能使湿润的淀粉—KI试纸变蓝的气体是                                                                 。
(a) Cl₂ (b) N₂O₄ (c) I₂蒸气 (d) SO₂ (e) O₃ (f) CO₂
（3）滴加浓盐酸前，分液漏斗首先要                                                                                                                      。
（4）过程III实验目的是                                                                                                                                                                                                                                                            。
（5）A中产生氯气的离子方程式为                                                                                                                                                                                                                                                       。
（6）B中浸有NaOH溶液的棉花作用是                                                                                              ，写出反应的离子方程式                                                                                                                                                                                                                                                                        。