问题 实验题

某强碱性溶液中可能大量存在K+、NH4+、Al3+、AlO2-、SO32-、SO42-、SiO32-、CO32-、Cl-、OH-中的某几种离子,现进行如下实验:

①取少量的溶液用硝酸酸化后,加Ba(NO3)2溶液,无沉淀生成。

②另取少量溶液逐滴加入盐酸,其现象是:一段时间后,开始产生沉淀并逐渐增多,沉淀量基本不变后产生一种气体,最后沉淀逐渐减少至消失。

(1)根据以上描述判断,肯定不存在的离子是___________________。

(2)按照反应顺序逐步书写出②中发生反应的离子方程式。

①H+ +OH-=H2O ②_______________ ③________________ ④HCO3-+H+=H2O+CO2↑ ⑤Al(OH)3+3H+=Al3+ +3H2O

(3)判断原溶液中是否存在K+,并说明理由______________________。

(4)向一定量的原溶液中加入10 mL 0.1 mol/L盐酸时,沉淀会完全消失,加入足量的硝酸银溶液可得到沉 淀0.19 g,则原溶液中是否含有Cl-?________________________。

答案

(1)Al3+、NH4+、SO32-、SO42-、SiO32-

(2)②AlO2-+H++H2O=Al(OH)3↓;③CO32-+H+=HCO3-

(3)含有,根据电荷守恒,溶液中一定有阳离子,而除了K+,不可能含有其他阳离子

(4)含有Cl-

阅读理解

The scientific world continues to be amazed by the speed of the development of cloning. Some scientists now suggest that the cloning of humans could occur in the near future. Despite the benefits of cloning, however, certain ethical (道德的) questions concerning the possible abuse (滥用) of cloning have been raised. At the heart of these questions is the idea of humans influencing life in a way that could harm society, either morally or in a real physical sense. Some people object to cloning because it allows scientists to "act like God" in the handling of living organisms.

   The cloning of Dolly raised the debate over this practice to a whole new level. It has become obvious that the technology for cloning Dolly could also be used to clone humans. A person could choose to make two or ten or a hundred copies of himself or herself by the same techniques used with Dolly. An active debate about the morality of cloning humans arises. Some people see benefits from the practice, such as providing a way for parents to produce a new child to replace one dying of a fatal disease. Other people worry about humans taking into their own hands the future of the human race.

   At the beginning of the twenty-first century, many scientists say the controversy over the ethics of cloning humans is overstressed because of the unpredictability (不可预测性) of cloning in general. While scientists have cloned animals such as sheep, mice, cows, pigs, and goats, fewer than 3 percent of all those cloning efforts have succeeded. The animal clones that have been produced often have health problems. Scientists believe the rapid reprogramming in cloning can introduce random (任意的) errors into a clone’s DNA. Those errors have altered individual genes in minor ways, and the genetic defects (缺陷) have led to the development of major medical problems. Some scientists say this should make human cloning out of the question, but others argue that cloning humans may actually be easier and safer than cloning animals. Whatever, I agree that further research in the field of cloning is needed.

小题1:Some people are against cloning of humans because they think _________.

A.the practice takes too much time and money

B.the cloning technology is still not mature

C.humans control the future of the human race

D.the population in the world will be too large小题2:Some scientists think the debate over ethics of cloning humans is overstressed because ____.

A.cloning of human beings is completely impossible

B.the result of cloning can’t be predicted in general

C.cloning of animals is a failure

D.there are big errors in a clone’s DNA小题3:We can learn from the text that _______.

A.cloning of humans is a very controversial issue

B.the cloning of Dolly begins to raise the debate over cloning of humans

C.there are medical problems in cloning animals

D.cloning humans is easier and safer than cloning animals小题4:The text is mainly about _______.

A.the benefits of cloning

B.the ethics of cloning

C.the history of cloning

D.the defects of cloning

单项选择题