问题 选择题

某溶液中存在较多的OH、K+、CO32,该溶液中还可能大量存在的是

A.SO42

B.Ca2+

C.NH4+

D.H+

答案

答案:A

题目分析:Ca2+与CO32-生成沉淀,Ca2+不能大量共存;NH4+能与OH-反应生成一水合氨或氨气和水,NH4+不能大量共存;H+与OH-生成H2O,H+不能大量共存。

点评:溶液中离子不能共存可能有以下几种情况:生成沉淀、生成气体、生成弱电解质、发生氧化还原反应等。

单项选择题 A3/A4型题
单项选择题

Nuclear power’s danger to health, safety, and even life itself can be summed up in one word: radiation.

Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can’t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can’t detect them, sense them, without a radio receiver. Similarly, we can’t sense radio activity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.

At very high levels, radiation can kill an animal or human being outright by killing masses of cells in vital organs. But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be significant. This is the case when only a few cells are hit. And if they are killed outright, your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in a deformed way. They can grow into cancer. Sometimes this does not show up for many years.

This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can he irradiated and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents.

Radiation can hurt us. We must know the truth.

Radiation can hurt us in the way that it can()

A. kill large numbers of cells in main organs so as to cause death immediately

B. damage cells which may grow into cancer years later

C. affect the healthy growth of our offspring

D. all of the above