问题 选择题

下列根据实验操作和现象所得出的结论不正确的是(   )

选项实验操作实验现象结论
A向硅酸钠溶液中滴加1滴酚酞,然后逐滴加入稀盐酸至红色褪去2 min后,试管里出现凝胶酸性:盐酸>硅酸
B在酒精灯上加热铝箔铝箔熔化但不滴落熔点:氧化铝>铝
C常温下,向浓硫酸中投入铁片铁片不溶解常温下,铁不与浓硫酸反应
D向某溶液中先滴加KSCN溶液,再滴加少量氯水先无明显现象,后溶液变成血红色溶液中含有Fe2,没有Fe3
 

答案

答案:C

A.试管里出现凝胶,说明生成硅酸,根据强酸制备弱酸的原理可知酸性:盐酸>硅酸,A正确;B.铝箔熔化但不滴落,原因是表面生成氧化铝膜,熔点较高,即熔点:氧化铝>铝,B正确;C.常温下,铁与浓硫酸发生钝化反应,而不是不反应,原因是在表面生成一层致密的氧化物膜而阻碍反应的进行,C错误;D.先无明显现象,后溶液变成血红色,说明溶液中含有Fe2,没有Fe3,氯水氧化Fe2生成Fe3,D正确

阅读理解

阅读理解

      It is often difficult for visitors to understand Americans lack of desire for privacy(隐私) . They are

not a nation of walled gardens and closed gates. Their yards normally run into one another without fences,

they often visit one another's homes without being invited or telephoning first, they leave their office doors

open while they work.

      Their lack of desire for privacy probable results from their history as a nation. America is a big

country.   There have never been walled cities in the United States, nor was there the need for Americans

to protect themselves from neighboring states. During the early years, America had so few settlers that

neighbors were very important, they were not to be shut out by doors and fences. Neighbors offered

protection and helped in the hard work of settling the land. They depended upon each other.

      From the nation's early history has come the desire for openness rather than privacy. Visitors will

notice this desire in a number of small ways, there may be rooms in American homes that do not have

doors or that have glass walls. If you notice that people forget to close your door when they leave your

room, do not think that this is rude, help them to learn that you would like it to be closed, or else become

used to new ways. In either case, be patient with the differences.

1. According to the passage, visitors to America sometimes have difficulty understanding ___.

A. Americans' openness

B. American's lack of desire for privacy

C. Americans' way of home

D. American's style of life

2. During the early years, people were never shut out by doors because ___ .

A. they were neighbors

B. they were friends

C. they depended on each other

D. they got used to that

3. Visitors will notice American's desire for openness in a way ___

A. they walled their houses with glass

B. they leave the office doors open while working

C. they never have fence

D. they depended upon each other

4. Which of the following is the best title for the passage?

A. No Walled Cities.

B. The Early Settlers

C. Americans' Lack of Desire for Privacy

D. be Patient with Differences

问答题 案例分析题