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问题 选择题

据报道，美国正在研究用锌电池取代目前广泛使用的蓄电池，它具有容量大、污染小的特点．其电池反应为：2Zn+O2=2ZnO，原料为锌、空气和电解质溶液，则下列叙述正确的是（　　）

A．锌为正极，空气在负极反应

B．负极的电极反应为：Zn-2e-+2OH-═ZnO+H2O

C．OH-在电解质溶液中向正极移动

D．电池工作时溶液的pH 降低

答案

A、锌的化合价升高，失去电子，发生氧化反应做原电池的负极，氧气得到电子的做正极，故A错误；

B、电解质溶液一定不是酸溶液，因为酸中不能生成氧化锌，所以是碱性电池，负极的电极反应为：Zn-2e-+2OH-═ZnO+H2O，故B正确；

C、OH-在电解质溶液中向负极移动，故C错误；

D、电池工作时，正极反应为：O2+2H2O+4e-=4OH-；溶液中氢氧根离子浓度基本不变，PH不变，故D错误；

故选B．

问答题

Ivan is an antiques dealer. He imported two extremely rare statues, created by the same sculptor, and placed an advertisement in a specialist magazine offering them for sale at a price of 1 million roubles per statue.Ekaterina replied to the advertisement immediately by post, agreeing to pay 1 million roubles to purchase one statue. However, she then had doubts about whether the statue would be a good bargain and sent a fax on the same day that her letter was despatched to say that she had changed her mind.On the same day, Leonid replied to the advertisement by post, confi rming that he would be prepared to pay 800.000 roubles for one statue.Having been away on a business trip for a few days, Ivan arrived at his offi ce and read the letter and fax sent by Ekaterina and the letter sent by Leonid. He sent faxes to both customers confi rming that he would supply the statues immediately. In the fax to Ekaterina he informed her that her fax could not cancel the deal as she had accepted his offer.On the same morning, Nikolai visited Ivan and offered to purchase both statues for 1.5 million roubles each. Ivan accepted this proposal and sold the statues immediately.Required:Advise Ekaterina, Leonid and Nikolai whether or not they have entered into legally binding contracts. (10 marks)
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多项选择题

依法治国方略的最终确立，在我们党和国家的发展史上的历史意义有（）。

A.依法治国方略的提出标志着我国建设社会主义法治国家的目标已经实现

B.依法治国是我们党治国理政观念的重大转变

C.依法治国是实现国家长治久安的重要保障

D.依法治国是发展社会主义民主政治的必然要求
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