【单选题】N A 为阿伏加德罗常数的数值,下列说法中正确的是( )
A.
在密闭容器中加入l.5mol H2和0.5molN 2 ,充分反应后可得到NH 3 分子数为N A
B.
一定条件下,2.3g的Na完全与O 2 反应生成3.6g产物时失去的电子数为0.1N A
C.
1.0L的0.1 mol·L-1Na2S溶液中含有的S 2- 离子数为0.1N A
D.
标准状况下,22.4L的CCl 4 中含有的CCl 4 分子数为N A
【单选题】Nowadays, college students are seen waiting on tables, cleaning in stores, advertising in streets, teaching in families and doing whatever work they can find. It has become fashionable for college stu...
【简答题】阅读短文。根据首字母填上适当的单词,把答案写在短文后1-10小题空白处。 Advertising: pros and cons In the m 1 world, advertising is everywhere! some people think that ads are great. O 2 hate ads, saying that they make our cities and co...
【简答题】(15分)实验室从含碘废液(除H 2 O外,含有CCl 4 、I 2 、I - 等)中回收碘,其实验过程如下: (1)向含碘废液中加入稍过量的Na 2 SO 3 溶液,将废液中的I 2 还原为I - ,其离子方程式为 ;该操作将I 2 还原为I - 的目的是 。 (2)操作X的名称为 。 (3)氧化时,在三颈烧瓶中将含I - 的水溶液用盐酸调至pH约为2,缓慢通入Cl 2 ,在40 0 C左右反应...
【单选题】Nowadays, college students are seen waiting on tables, cleaning in stores, advertising in streets, teaching in families and doing whatever work they can find. It has become fashionable for college stu...
【单选题】The author's attitude toward online advertising can be summarized as one of
A.
reserved consent but discontent.
B.
objective analysis void of opinions.
C.
enthusiastic support but slight contempt.
D.
approval so far but uncertainty in the future.
【单选题】某温度时在CCl4溶液中发生N2O5的分解反应【图片】,2.10 mol/LN2O5反应10 min后其浓度为1.30mol/L,则这段时间内反应的平均速率为( )【图片】。
【简答题】Frank Work Experience went to a p___(1)___ company (私营公司) changed to a Sino –Japanese joint-venture enterprise(中日合资企业) and worked as a __(2)__ ______ two years later, moved on to a c___(3)____ compan...