问题
选择题
将一小块金属钠久置于空气中，有下列现象：①生成白色粉末 ②变暗 ③生成白色固体 ④发生潮解这些现象的先后顺序是( )
A．①②③④
B．④③②①
C．②③④①
D．①③④②
答案
答案：C
金属钠放置在空气中会被空气中的氧气氧化而变暗，生成的氧化钠与水反应产生NaOH固体，最后转化为碳酸钠固体粉末。
搜题请搜索小程序“爱下问搜题”
将一小块金属钠久置于空气中，有下列现象：①生成白色粉末 ②变暗 ③生成白色固体 ④发生潮解这些现象的先后顺序是( )
A．①②③④
B．④③②①
C．②③④①
D．①③④②
答案：C
金属钠放置在空气中会被空气中的氧气氧化而变暗，生成的氧化钠与水反应产生NaOH固体，最后转化为碳酸钠固体粉末。
Grades aren’t everything, but if you or your parents are worried about your report cards, try some of these easy tips. 小题1:____________________Find out how much time you need to spend on each subject every week, and figure out from your teachers when the homework is due, and then make a schedule. According to the schedule, you are able to make a study pan. 小题2:_________________.Most teachers base grades on homework, and it’s easier to keep up with your assignments(作业) than it is to dig yourself out of a hole. 小题3:_________________Your teachers may have suggestions about what you can do to learn more and improve what you can’t. But you have to ask! 小题4:___________________When you get a bad grade, you probably get angry and sad. That’s normal, but you should also use the experience to try to figure out what went wrong so you can avoid the same mistake in the future. Study with your friends. Sometimes it’s hard to get started on homework, so you may meet with one or two friends to do your work. But this won’t work if you and your friends decide to watch TV or play video games instead of doing your homework!
|