【简答题】甲酸钙广泛用于食品、化工、石油等工业生产上,300~400℃左右分解。Ⅰ、实验室制取的方法之一是:Ca(OH) 2 +2HCHO + H 2 O 2 = Ca(HCOO) 2 + 2H 2 O + H 2 ↑。 实验室制取时,将工业用氢氧化钙和甲醛依次加入到质量分数为30-70%的过氧化氢溶液中(投料物质的量之比依次为1∶2∶1.2),最终可得到质量分数98%以上且重金属含量极低的优质产品。 (1...
【单选题】下颌第一磨牙牙冠上不可能有的发育沟是( )。
【单选题】How have new media changed how consumers access the news?
A.
Now they spend much more time online?
B.
Thay have control over when and what news the watch.
C.
They share the news with their friends on social media sites.
D.
They don't watch the news as much anymore.
【单选题】Good News Beats Bad on Social Networks Bad news sells. If it bleeds , it leads . No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning ...
A.
Good news can spread faster and farther than disasters.
B.
When you share a story with your friends, you don’t care how they react.
C.
Wordofmouth communication tended to be more positive than negative.
D.
The more positive an article, the more likely it was to be shared.
【单选题】How have new media changed how consumers access the news?
A.
Now they spend much more time online.
B.
They have control over when and what news they watch.
C.
They share the news with their friends on social media sites.
D.
They don’t watch the news as much anymore.