、
、
(超氧化氢)等都属氢氧化合物,其中
又叫超氧酸,与
化学性质相似,又与
(
、
、I等)某些性质相似,下列说法错误的是( )
溶液中滴入品红溶液,品红褪色,加热后红色不恢复
B .
在碱中能稳定存在
C .
不稳定,分解会生成氧气
D .
可与
溶液反应:
中,
,
,如果点
由点
出发沿
方向向点
匀速运动,同时点
由点
出发沿
方向向点
匀速运动,它们的速度分别为
和
,
,分别交
,
于点
和
,设运动时间为
.
,若运动时间
时,
;
,当
的面积为
时,求
的值;
,求
的值.

B .
C .
D .
C . 4F
D . 2F
The Spring Festival was supposed to be a time for family gathering.
One of the main reasons that the novel coronavirus has been spreading so quickly is that it's transmitted through droplets (飞沫) coughed and sneezed by infected people. These droplets can travel as far as two meters in the air. And even after the droplets fall and land on surfaces, they can stay alive for up to five days. This means everything you touch in a public place might be giving you this deadly virus.
In a new development, it seems possible that the virus can be transmitted through aerosol (气溶胶), which is a suspension (悬浮) in the air (or in gas) of fine solid particle (微粒) or liquid droplets. However, no further evidence has been found to support this statement.
Avoiding people and public spaces is not how we planned to spend this festival season. Firstly, we've developed better habits, including washing our hands thoroughly after coming home. We've also learned to value the simple happiness - being able to take a walk, going to a restaurant or hanging out with friends.
Try thinking about all the things you'll be free to do after this terrible virus is defeated.
A. This makes it dangerous to get too close to people.
B. But perhaps we can look on the bright side.
C. Even so, it's one more reason for you to stay home.
D. Then you'll find the idea of staying at home for now is not so unbearable (无法忍受的).
E. But that tradition came to a stop this year because of an epidemic outbreak.
| 选项 | 实验目的 | 实验方案 |
| A | 验证NaOH在空气中部分变质 | 加水充分溶解后,滴加CaCl2溶液 |
| B | 除去KNO3溶液中的AgNO3 | 加适量KCl溶液,过滤 |
| C | 鉴别氯化铵、尿素和氯化钾三种化肥 | 取样,加入熟石灰粉末,研磨 |
| D | 除去ZnSO4溶液中的H2SO4 | 加入足量氧化铁粉,过滤 |
①生命的价值在于对他人、对社会的贡献 ②生命的价值靠行动来实现
③生命的意义需要自己发现和创造 ④生命的意义在于享受生活
—It ___________ great. But I ___________ tired now.
﹣
=1(x≠0)
B .
+
=1(x≠0)
C .
﹣
=1(y≠0)
D .
+
=1(y≠0)
|
硬币总数/枚 |
|||||
|
1元/枚 |
|||||
|
5角/枚 |
|||||
|
总钱数/元 |
①世界性贸易给拉美殖民地创造了财富 ②美国的独立鼓舞了拉美人民
③工业革命壮大了拉美各国的实力 ④法国大革命打击和削弱了西班牙