问题 填空题

(15分)云南省曲靖的铬渣污染经媒体报道后,铬污染再次引起人们的关注。利用化学原理可以对工厂排放的含铬废水、铬渣等进行有效处理。

I.含铬废水的处理:某企业排放的含铬废水中含有较多毒性较大的Cr2O72-,某研究性学习小组为了变废为宝,将废水处理得到金属铬,设计了如下的工艺流程。

(1)加酸调节到pH=6,则用pH试纸测定溶液pH的操作是:                      

(2)在含Cr2O72-废水中存在着平衡:Cr2O72-+H2O2CrO42-+2H+,请写出该平衡的平衡常数表达式k=            ,若继续加水稀释,平衡将    移动(填“正向”、“逆向”“不”)。

(3)请写出通入SO2时发生的离子反应:                         

(4)写出加入铝粒时发生反应的化学方程式               ,该反应是焓     (填“增加”或“减少”)反应。

II.铬渣的处理

铬渣烧结炼铁法:铬渣中约含有55%的氧化钙和氧化镁,此外还含有15%左右的氧化铁,这些都是炼铁所需的成份。少量的铬渣代替消石灰同铁矿粉、煤粉混合,经烧结后送入高炉冶炼,六价铬还原为三价铬或金属铬,金属铬熔入铁水,而其它成分熔入熔渣。炼铁可使铬渣彻底解毒并充分利用,是铬渣治理的良好方法之一。

碱性溶液还原法:直接在碱性铬渣中加入硫化钠等进行六价铬的还原反应,形成Cr(OH)3沉淀后,过滤回收铬污泥。

(5)铬渣烧结炼铁法中煤粉的作用是                                  。(写两点)

(6)请配平碱性溶液还原法中发生的离子反应:□Cr2O72+□S2+□H2O=□Cr(OH)3+□S2O32+□OH

答案

(1)将一小块pH试纸放在表面皿上,用玻璃棒蘸取少量待测液,点在pH试纸上,再与标准比色卡对照。(2分)

(2)c(CrO42-)2c(H+)2/c(Cr2O72-)(2分)  正向(2分)

(3)Cr2O72+3SO2+2H+=2Cr3++3SO42-+ H2O(2分)

(4)2Al+Cr2O3Al2O3+2Cr(2分)  焓减少(1分)

(5)为高炉冶炼过程提供热源;燃烧后生成的CO是高炉冶炼过程的还原剂;还起到高温填料的作用(写两点即可)(2分)

(6)4  6  19  8  3  14 (2分)

(1)测定溶液的pH的方法是:用玻璃棒蘸取待测溶液滴在pH试纸的中心位置,然后对照标准比色卡,读出对应颜色的数据。

(2)水为纯液体,浓度为常数,在平衡常数表达式中不出现;加水稀释,使c(Cr2O72-)、c(CrO42-)、c(H+)均减少,该反应的浓度商公式中,分子减少的更快,使浓度商<平衡常数,平衡正向移动。

(3)根据流程图分析Cr2O72转化为Cr3+,SO2一般是转化为SO42-,根据化合价升降法配平方程式。

(4)铝热反应是放热反应,即焓减少反应。

(6)根据化合价升降法配平方程式。

阅读理解
阅读理解。
      When you want to go shopping, decide how much money you can spend on new clothes, think about
the kind of clothes you really need, then look for those clothes on sale. There are labels (标签) inside all
new clothes. The labels tell you how to take care of your new clothes. The label for a shirt may tell you to
wash it in warm water. A sweater label may tell you how to wash in cold water. The label on a coat says
"dry clean only" Washing may ruin (损坏) this coat. If you do as the directions (说明) say on the label,
you can keep your clothes looking their best.
     Many clothes today must be dry cleaned. Dry cleaning is expensive. When buying new clothes, check
to see if they will need to be dry cleaned. You will save money if you buy clothes that can be washed. You
can save money if you buy clothes that are well made. Well-made clothes last longer. They look good even
after they have been washed many times. Clothes that cost more money are not always better made. They
do not always fit better, Sometimes less expensive clothes look and fit better than more expensive clothes.
1. The labels inside clothes tell you            .
[ ]
A. How to save money
B. how to keep them looking their best
C. if they fit you
D. where to get them dry clean
2. The label say "dry clean only" on a coat means            .
[ ]
A. the coat is hard to dry
B. the coat is easy to dry
C. you can not wash it in water
D. the coat is always dry and clean
3. The first thing for you to do before you buy clothes is            .
[ ]
A. to see how much money you can pay
B. to look for well-made clothes
C. to know how to wash them
D. to read the label inside
4. If you want to save money,you can buy clothes that            .
[ ]
A. don't fit it
B. do not last long
C. need to be dry cleaned only
D. can be washed
5. From the passage we know that cheaper clothes            .
[ ]
A. are always worse made
B. must be dry cleaned
C. can not be washed
D. can sometimes fit you
单项选择题