问题
选择题
若NA代表阿伏加德罗常数，则下列叙述正确的是（ ）
A．16g氧气和臭氧的混合物中原子的数目0.5NA
B．1mol Cl2与足量的铁完全反应，转移的电子数为2NA
C．1 L 0.5mol·L－1AlCl3溶液中含有的Al3+数目为0.5NA
D．在标准状况下，22.4L HCl与22.4L H2O2所含有的电子数均为18 NA
答案
答案：B
搜题请搜索小程序“爱下问搜题”
若NA代表阿伏加德罗常数，则下列叙述正确的是（ ）
A．16g氧气和臭氧的混合物中原子的数目0.5NA
B．1mol Cl2与足量的铁完全反应，转移的电子数为2NA
C．1 L 0.5mol·L－1AlCl3溶液中含有的Al3+数目为0.5NA
D．在标准状况下，22.4L HCl与22.4L H2O2所含有的电子数均为18 NA
答案：B
| 阅读理解。 | |||||||||||||||
| It is said that all the dreams serve a purpose (目的). While there is no agreement among scientists about why we dream, there are many ideas about the different kinds of dreams we have. One common kind of dream is the repeating dream, in which the same story is repeated again and again, often for many months or even years. Some believe these are a sign people have a problem in their life and once that problem is gone then the dream will stop. Others think they are a way to help people remember something very important. Another well-known kind of dream is the nightmare. The pictures and stories in such dreams make people very afraid and dreamers usually remember them far more clearly than normal dreams. The cause of such dreams may be seeing something frightening such as a car accident or some dead snakes. Others think such dreams may be trying to make a person pay attention to something that is dangerous in their life. Daydreams happen during wake-time when we forget where we are or what we are doing and find ourselves in a made-up story or unreal word. We often daydream when we are doing something that is not interesting or exciting. They help us think about our future. Lucid (清醒的) dreams are the most fun. These happen when dreamers suddenly understand that they are dreaming. Instead of waking up, they stay in the dream and are able to control what happens in the dream as if they are making a movie.
|