问题 问答题

以下是某实验小组用CO2和NaOH溶液做喷泉实验的装置和测得的一组数据

NaOH浓度(mol/L)00.40.50.81.01.41.61.8
现象不能

形成

一段

液柱

形成喷泉形成喷泉形成喷泉形成喷泉形成喷泉形成喷泉
时间6min1min35s10s6s6s
烧瓶中水的体积(mL)74171125240240
已知:烧瓶最大容量为250mL,每次实验充分摇动烧瓶,只有NaOH浓度不同,其它条件和操作方式相同.结合喷泉实验原理及你所学的知识,判断下列说法中不正确的是______

A.CO2在水中的溶解度小,不宜用水直接吸收CO2来做喷泉实验

B.在一定的浓度范围内氢氧化钠溶液的浓度越大越易形成喷泉

C.NaOH浓度为1.6mol/L时,CO2还没有全部分被吸收

D.当氢氧化钠溶液的物质的量浓度为1.0mol/L时所得溶液不可能有氢氧化钠,烧瓶也没有充满.

答案

A、该实验是用CO2与氢氧化钠溶液完成的,因为CO2在水中的溶解度并不大,不能形成喷泉,故A正确;

B、表中数据显示NaOH浓度在<1.6mol/L前有浓度越大越易形成喷泉(形成喷泉所需时间短)的规律,故B正确;

C、表中数据显示NaOH浓度在>1.6mol/L时CO2已完全被吸收,生成的Na2CO3达最大值,水的体积没有达到烧瓶最大容量,是因为烧瓶中有导管等,故C错误;

D、表中数据显示形成喷泉所需时间最短为6s,说明此时氢氧化钠已足量(或过量),当氢氧化钠浓度为1.4mol/L时仍不是最快的,故氢氧化钠浓度为1.0mol/L时为不足量,因此不能完全吸收CO2,溶液中无氢氧化钠剩余,烧瓶也不能充满,故D正确.

故选C.

阅读理解

阅读理解

     A lot of people are their own enemies. They regard themselves as unlikely to succeed in college and

often feel that there have been no accomplishments (成就) in their lives. In my first year of college

especially, I saw people get themselves down too quickly. There were two students in my class who failed the first test and seemed to give up immediately. From that day on, they walked into the classroom carrying defeat on their shoulders the way other students carried textbooks under their arms. When they

disappeared for good(长久地), no one took much notice, for they had already disappeared in spirit after

that first test.

     I have really wanted to shake them by the shoulders and say: "You are not dead. Be proud and pleased that you have brought yourself here to college. Breathe. Hope. Act." Such people should not use

self-doubts as an excuse for not trying. They should pull themselves together and get to work. They should start taking notes in class and trying to learn. Above all, they should not give up without even trying.

1. The phrase "get themselves down" (Para. 1) probably means ______.

A. tell lies  

B. lose confidence    

C. avoid dangers    

D. waste time

2. When the two students dropped out (退学), no one took much notice because ______.

A. they had long lost heart in class performance

B. they were absent from class too often

C. they didn't get on well with other students

D. they were so much cut off from the rest of the class

3. According to the passage, the two students failed in their study because of their ______.

A. shyness    

B. proudness    

C. self-doubt    

D. laziness

4. The author thinks that the two students should ______.

A. give up their college education        

B. learn from other students

C. feel happy because they are in college      

D. try hard before giving up

名词解释