【简答题】IEEE 802.11 标准支持哪几种类型的无线网络拓扑?
【简答题】标准状况下,1 L水溶解500 L氨气所得氨水的密度为0.9 g·mL -1 ,求此氨水的质量分数、物质的量浓度各为多少。
【简答题】密度为 1.84Kg/L ,质量分数为 0.98 的浓硫酸的物质的量的浓度为
【单选题】What do you often do with your friends?
A.
I like them very much.
B.
We often play together.
C.
They are my good friends.
【多选题】What do you often do in the library?
B.
We often borrow books from the library.
C.
We often have meetings here.
D.
We often sing and dance here.
【单选题】What do you often do with your family?
【简答题】现有溶质质量分数为98%、密度为1.84kg·L -1 的浓硫酸,若用其配制1.0mol·L -1 的稀硫酸250ml。回答下列问题: (1)需要98%的浓硫酸 ml(计算保留两位小数)。 (2)配制时,要用到的玻璃仪器除量筒、烧杯、玻璃棒外,还需 。
【简答题】标准状况下.空气密度为1.293g/L,氧气的密度为1.429g/L,则空气中氧气的质量分数是多少?