题目

（16分）环境中常见的重金属污染有：汞、铅、锰、铬、镉。处理工业废水中常含有的Cr2O2-7和CrO2-4离子，常用的方法有两种。    方法1：还原沉淀法    该法的工艺流程为：    其中第①步存在平衡：   （1）写出第①步反应的平衡常数表达式                              。   （2）关于第①步反应，下列说法正确的是          。       A．通过测定溶液的pH值可以判断反应是否已达平衡状态B．该反应为氧化还原反应C．强酸5、Christmas Eve means a warm get-together with friends, a candlelight dinner, or perhaps a celebration at a pub（酒馆）for students. But, for Cai Yingjie, the night has a different meaning:  helping beggars（乞丐）and the homeless（people without homes） Cai, who is a student in journalism at Tsinghua, could be found at Beijing's Wudaokou Light Railway Station that special evening. When she saw an old beggar, she took the cold, rough hands of the woman with her warm, clean hands, and gave the woman some warm bread and helped her put on a pair of new gloves（手套） The woman was surprised for a few seconds, then burst into tears, saying "for the first time I feel respected （尊重） Cai said, "A beggar's life is very hard. That's why I want to help them." Cai was one of 14 Tsinghua students spending Christmas Eve among the poor. They walked in the end wind along the streets from 4 to 7 pm on Friday, visiting 15 beggars in Beijing's Haidian District. They brought bread and gloves with them, and Stopped to greet beggars and offer them some of the warm food. Each beggar greeted them with a look of surprise. "'I know the activity can't help much, but it's meant to show our respect and care for beggars and the homeless who have been neglected for so long, "said Sun,  head of the group. "And Christmas is a good time for that." 1．What does Christmas Eve mean to the 14 Tsinghua students? A．Taking 15 beggars to Tsinghua. B．Getting together with friends. C．Showing care to the beggars and the homeless, D．Selling bread and gloves to the beggars. 2．What does the beggar mean by saying "for the first time I feel respected"? A．The beggar has been waiting for Cai for long. B．The beggar hasn't been shown care for so long. C．The beggar has been respecting Cai for a long time. D．This is the first time the beggar has seen Tsinghua students. 3．What did each beggar feel when they received greetings'? A．Sad.                     B．Amazed. C．Frightened.             D．Proud.