问题 实验题

(12分)(1)学习二氧化碳性质时,老师做了如右图所示的实验。结果发现,澄清石灰水变浑浊。请写出澄清石灰水变浑浊有关反应的化学方程式_____________________。

老师提出:氢氧化钠与氢氧化钙同属于碱类化合物,与氢氧化钙的化学性质相似,那么,氢氧化钠能否与二氧化碳反应呢?

同学们围绕着这个问题,通过查阅资料得知:常温下,CO2+2NaOH=Na2CO3+H2O。

接着,在老师指导下,完成了如下实验:将上述实验中的澄清石灰水换成氢氧化钠溶液,向其中通入CO2,观察到的实验现象为_________________________。

(2)为了验证CO2能与氢氧化钠发生化学反应,同学们设计了如下实验

①甲实验:向盛满CO2的塑料矿泉水瓶(质软)中加入一定量NaOH溶液,迅速旋紧瓶塞,并振荡。静止一会儿后观察到的实验现象为________________________。

②乙实验:向盛满CO2的集气瓶中倒入一定量NaOH溶液,迅速在瓶口处塞上一个去壳熟鸡蛋,静止一会儿后可观察到的实验现象为________________________。

(3)做完上述实验后,部分同学提出质疑,认为上述实验不足以说明CO2与氢氧化钠发生了化学反应。你认为这部分同学提出上述质疑,主要考虑的干扰因素是________________。为了进一步验证CO2能与氢氧化钠发生化学反应,同学们又设计了如下实验:

①A瓶盛装的试剂是________________,B瓶盛装的试剂是______________,实验时应_____

[填“打开”或“关闭”]活塞K。

②进行此实验时,通入CO2的体积应__________[填“大于”、“等于”或“小于”]A瓶溶液的体积。

③能证明CO2能与氢氧化钠发生化学反应的实验现象是______________________________。

答案

(12分)

(1)CO2+Ca(OH)2=CaCO3↓+H2O。无明显变化。

(2)①塑料瓶变瘪    ②鸡蛋被吞入瓶中

(3)可能是CO2溶于水造成塑料瓶变瘪。

①NaOH溶液,澄清石灰水,关闭。

②大于

③A、B中均无明显现象。

(1)二氧化碳可以和澄清石灰水反应生成白色沉淀,可以据此写出其反应的化学方程式,而二氧化碳与氢氧化钠反应生成的是可溶性的碳酸钠和水,所以没有明显现象;

(2)①二氧化碳溶于氢氧化钠后,会使塑料瓶内的压强减小,大气压就会把塑料瓶压瘪了;

②二氧化碳溶于氢氧化钠后,会使塑料瓶内的压强减小,大气压就会把鸡蛋压入瓶中;

(3)由于二氧化碳也会溶于水,所以上述实验不足以说明CO2与氢氧化钠发生了化学反应;

①要探究二氧化碳能否与氢氧化钠反应,必须有氢氧化钠,而验证是否充分反应则需要借助于氢氧化钙溶液,所以在A装置中装入氢氧化钠溶液,而在B装置中装入氢氧化钙溶液,开始实验时为了让二氧化碳通过氢氧化钠溶液应该将活塞K关闭;

②二氧化碳在水中的溶解力为一体积的水溶解一体积的二氧化碳,所以为了排除水的干扰,通入二氧化碳的体积应该大于A中液体的体积;

③最终如果B装置中的澄清石灰水不变浑浊,则说明在二氧化碳与氢氧化钠溶液发生了反应.

故答案为:

(1)CO2+Ca(OH)2═CaCO3↓+H2O;无明显变化;

(2)①塑料瓶变瘪;

②鸡蛋被吞入瓶中;

(3)可能是CO2溶于水造成塑料瓶变瘪;

①NaOH溶液;澄清石灰水;关闭;

②大于;

③A、B中均无明显现象.

选择题
单项选择题

Computer programmer David Jones earns £35,000 a year designing new computer games, yet he cannot find a bank prepared to let him have a check card. Instead, he has been told to wait another two years, until he is 18.
The 16-year-old works for a small firm in Liverpool, where the problem of most young people of his age is finding a job. David’s firm releases two new games for the expanding home computer market each month.
But David’s biggest headache is what to do with his money. Despite his salary, earned by inventing new programs within fight schedules, with bonus payments and profit-sharing, he cannot drive a car, take out a mortgage, or obtain credit cards.
He lives with his parents in their council house in Liverpool, where his father is a bus driver. His company has to pay £150 a month in taxi fares to get him the five miles to work and back every day because David cannot drive.
David got his job with the Liverpool-based company four months ago, a year after leaving school with six O-levels and working for a time in a computer shop. "I got the job because the people who run the firm knew I had already written some programs," he said. "I suppose £35,000 sounds a lot but actually that’s being pessimistic. I hope it will come to more than that this year." He spends some of his money on records and clothes, and gives his mother £20 a week. But most of his spare time is spent working.
"Unfortunately, computing was not part of our studies at school," he said. "But I had been studying it in books and magazines for four years in my spare time. I knew what I wanted to do and never considered staying on at school. Most people in this business are fairly young, anyway." David added, "I would like to earn a million and I suppose early retirement is a possibility. You never know when the market might disappear.\

Why is David different from other young people of his age

A. He earns an extremely high salary.
B. He is employed.
C. He does not go out much.

D. He lives at home with his parents.