问题 选择题

含CrO72-的工业酸性废水会造成铬污染,排放前要先进行如下处理:①先将Cr2O72-还原成Cr3+②往废水中加入适量NaCl后,以Fe为电极进行电解,同时鼓入空气。从而使溶液的pH不断升高,废水由酸性转化为碱性,Cr3+即变为不溶性氢氧化物除去。处理该废水的过程中,溶液pH不断升高的原因是下列反应事实中的  

A.电解时废水体积不断减小

B.电解时H+在阴极处被还原

C.作为阳极的Fe不断溶解

D.Cr2O72-转化为Cr3+没有消耗H+

答案

答案:B

①以Fe为电极电解NaCl溶液时,阳极Fe不是惰性电极,通电时本身首先被氧化:

阳极(Fe):Fe-2e=Fe2+(氧化)

阴极(Fe):2H2O+2e=H2↑+2OH-(还原)

所以电解过程中pH升高。

②Cr2O72-在酸性条件下是强氧化剂,是将Fe2+氧化成Fe3+而本身被还原成Cr3+:

Cr2O72-+6Fe2++14H+=2Cr3++6Fe3++7H2O

此反应的发生亦使pH升高。

③Cr3+,Fe3+在pH升高到一定值时,便与OH-结合生成Cr(OH)3,Fe(OH)3沉淀而除去:

Fe3++3OH-=Fe(OH)3↓,Cr3++3OH-=Cr(OH)3↓

④以Fe做电极的作用:提供还原剂Fe2+。通入空气的作用:过量的Fe2+会以Fe(OH)2沉淀,空气中O2会使其氧化成Fe(OH)3:

4Fe(OH)2+O2+2H2O=4Fe(OH)3↓

阅读理解

There are some famous buildings that everyone can recognize. When you see a picture of a sports stadium that reminds you of a bird’s nest, you probably know it is the Olympic stadium in Beijing. When you see a picture of a famous concert hall that reminds you of a sailing ship, you probably know it is the Sydney Opera House in Australia. Buildings like these are easily recognized everywhere in the world. They were designed to look like other things if people use their imaginations.

Other buildings do not need any imagination. They are made to look exactly like other things. Sometimes, these buildings are offices, restaurants, or even houses. Three buildings built in this way are actually museums. The shape of the building is clue to the objects people can see inside.

In Guizhou, China, people can visit the Meitan Tea Museum, built in the shape of a giant teapot. There is also a second building next door that is shaped like a huge tea cup. From far away, the nine-story teapot-shaped museum looks like some kinds of giant work of art. But as one gets closer, the windows make it clear that this is a building.

People who are interested in guitars might want to visit the Guitar Museum in Tennessee, USA. The three-story building is shaped like a guitar lying on its side. Inside, visitors can see all kinds of guitars as well as learn about famous guitar players. 

One of the newest funny shaped museums is a pottery museum in Gyconggi, Korean museum, built in 2011, is shaped just like a traditional Korean pot, Along with seeing exam pots and tools used for making pots in the museum, visitors can try to make their own pots.

小题1:Sydney Opera House look like_______and it is in Australia.

A. a bird’s nest    B. a sailing ship    C. a nice guitar

小题2:People can visit the building in the shape of teapot__________.

A. in Guizhou, China   B. In Tennessee, USA   C. in Gycouggi, Korea

小题3:The underlined word” giant” means “_________” in Chinese.

A.豪华的     B. 巨大的     C. 古老的

小题4: Which is NOT true about the building that is shaped like a guitar?

A. People can see all kinds of guitars inside of it.

B. You can find information about famous guitar players there.

C. The two-story building is shaped like a guitar lying on its side.

小题5:The Olympic stadium and the Sydney Opera House are examples of ________.

A. buildings that look exactly like things in them

B. buildings that look like other things

C. buildings that look like famous things

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