问题 选择题

用石墨作电极,电解1mol/L下列物质的溶液,溶液的pH值保持不变的是(  )

A.HCl

B.NaOH

C.K2SO4

D.NaCl

答案

A、电解盐酸,溶液中氢离子、氯离子放电,所以溶液中氢离子浓度逐渐减小,pH值逐渐变大,故A错误.

B、电解氢氧化钠,溶液中氢离子、氢氧根离子放电,相当于电解水,导致溶液中氢氧化钠的浓度增大,溶液的pH值增大,故B错误.

C、电解硫酸钾溶液,溶液中氢离子、氢氧根离子放电,相当于电解水,导致溶液中硫酸钾的浓度增大,但溶液中氢离子和氢氧根离子的浓度不变,所以溶液的pH值保持不变,故C正确.

D、电解氯化钠,溶液中氢离子和氯离子放电,所以溶液中氢离子浓度逐渐减小,pH值逐渐变大,故D错误.

故选C.

完形填空

第二节阅读下面短文,回答文章后面的5个问题。

(E)

Most people agree that the direct, assertive(过分自信的) American personality is a virtue, but it sometimes surprises foreigners. In many cultures, respect for older people or those in positions of authority keeps others from expressing their true feelings. But in the US children often argue with their parents, students may disagree with their teachers, and citizens may express opposition to the actions of government. If the soup has a fly in it or the meat is too tough to chew, the diner can complain to the waiter, if the boss makes a mistake, an employee will politely point it out.

Some  straight talks about the American personality must include the admission that Americans have their faults. The extremely competitive nature of Americans is probably their worst fault. Of course, competition isn’t always bad. As a matter of fact, it promotes excellence by encouraging individuals and business to try to do their best. But the desire to get ahead of others sometimes causes people to do things that are unkind and even dishonest. Also, Americans admire what is practical, fast, efficient, and fresh. Sometimes they fail to understand and appreciate practices that have greater respect for more traditional, leisurely ways of doing things. On the other hand, people from other cultures may dislike the practical, challenging American lifestyle.

Despite culture differences, most foreigners give Americans credit for their virtues. Americans are generally viewed as friendly, adaptable, energetic, and kindhearted. Most newcomers to the US like Americans, and the feeling is usually mutual.

Perhaps the greatest American virtue is a deep interest in new ideas and new people. In a nation of immigrants, the foreigner does not remain an outsider for long.

61.What does the passage mainly talk about? (No more than 5 words) 

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62.According to the passage, why do people outside America tend to avoid expressing their true feelings when they see their parents or teachers make a mistake? (No more than 15 words)

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63.Why is extremely competitive nature considered as one of the American faults?( No more than 20 words)

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64.What does the writer mean by saying “most foreigners give Americans credit for their virtues”? (No more than 10 words)

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65.Please explain the underlined word “immigrant” in English. (No more than 10 words) _____________________________________________

判断题