问题 填空题

电解原理在工业中有广泛应用。右图表示一个电解池,装有电解液a ;X、Y是两块电极板,通过导线与直流电源相连。请回答以下问题:

(1)若X、Y是惰性电极,a是200mLNaCl溶液,实验开始时,同时在两边各滴入几滴酚酞溶液,则电解池中X极上的电极反应为_____,在X极附近观察到的现象是 :_______。Y电极上的电极反应式是_________,检验该电极反应产物的方法是 :________________。当外电路通过0.02 mol电子时,充分混合电解后的溶液,忽略溶液体积变化,理论上溶液的PH值为_______。

(2)如果用电解方法精炼粗铜,电解液a选用CuSO4溶液,则X电极的材料是_________,Y电极的材料是______,Y电极反应式是_______________。

答案

(每空1分,共8分)(1)2H++2e-=H2↑  有气泡,溶液变红   2Cl-—2e-==Cl2

把湿润的淀粉KI试纸放在Y极附近,试纸变蓝,说明Y极产物为Cl2     13

(2)纯铜   粗铜   Cu-2e-==Cu2+

题目分析:(1)根据装置图可知,和电源的负极相连的电极X极是阴极,该电极上氢离子发生得电子的还原反应,即2H++2e-=H2↑。由于氢离子放电,破坏了阴极周围水的电离平衡,则阴极周围溶液显碱性,即在X极附近观察到的现象是有气泡,溶液变红;和电源的正极相连的电极Y极是阳极,该电极上氯离子发生失电子的氧化反应,即2Cl-—2e-==Cl2↑。氯气具有强氧化性,据此可以鉴别,即把湿润的淀粉KI试纸放在Y极附近,试纸变蓝,说明Y极产物为Cl2 。当外电路通过0.02 mol电子时有0.02mol氢离子放电,则生成OH的物质的量就是0.02mol,所以溶液中中OH的浓度是0.02mol÷0.2L=0.1mol/L,则pH=13。

(2)电解方法精炼粗铜,电解池的阴极材料是纯铜,电极反应为:Cu2++2e-=Cu;电解池的阳极材料是粗铜,电极反应为:Cu-2e-=Cu2+

点评:该题是高考中的常见题型,属于中等难度的试题。试题难易适中,基础性强。该题需要注意的是明确图中电源的正负极确定电解池的阴阳极是解答的关键,并熟悉电极反应及离子的放电顺序来解答,有利于培养学生的逻辑推理能力和规范答题能力,提高学生灵活运用基础知识解决实际问题的能力。

阅读理解

阅读理解。(每小题2分,共30分)

阅读下列材料,从 A、B、C、D 四个选项中选出最佳答案,并把答题卡上对应题目的答案标号涂黑。

A

People say that George Washington, the first president of the United States, never told a lie. But it seems that the president was not without faults.

A New York library recently found that Washington borrowed two books from the library in 1789. He didn’t return them.

If he were still alive, he would have to pay the library $300,000 for being 220 years late.

On October 5, 1789, when the first president borrowed the books form the New York Society Library, he didn’t sign his name in the borrower’s book. He just wrote “president” to show who had taken them out.

The two books should have been brought back a month later but were never returned. Workers at the library realized the books were missing.

The New York Society Library doesn’t expect anyone to pay the fine. But it hopes that someone will return the books.

小题1:Gorge Washington is__________.

A.the president of the US now

B.the first president of the US

C.the first black president of the US

D.the president who always borrowed the books without returning them back小题2:Gorge Washington borrowed a book from ________.

A.the Washington Public Library

B.the New York Society Library

C.the Paris Society Library

D.the Chinese Public Library小题3:The library hopes _________.

A.Gorge Washington will return the book.

B.Gorge Washington will pay the fine

C.someone will find the book and return it

D.someone will pay the fine for the president

单项选择题