;
.
sweater 判断: 抄写或改正:()
2C(气)若经 2秒后测得 C 的浓度为0.6 mol·L-1 , 现有下列几种说法:①用物质 A 表示反应的平均速率为 0.3 mol·L-1·s-1②用物质 B 表示的反应的平均速率为 0.6 mol·L-1·s-1③ 2 s 时物质 A 的转化率为30% ④ 2 s 时物质 B 的浓度为 1.4 mol·L-1 , 其中正确的是( )
①37.8÷25÷4
②3.84+4.6+5.16
③2.4÷
×
④
⑤63.5×25%+0.25×36.5
⑥
中,
,
,则公比等于( )
|
时间(min) |
0 |
10 |
20 |
30 |
40 |
… |
150 |
180 |
|
泡沫塑料组水温(℃) |
90 |
74 |
65 |
60 |
57 |
… |
21 |
20 |
|
棉絮组水温(℃) |
90 |
70 |
55 |
? |
33 |
… |
20 |
20 |
分析实验数据可知,他们实验时室内的温度是℃;从计时开始到40min后,泡沫塑料包的水温度降低了℃,而棉絮包的水温度降低了℃,由此你能看出,在这两种材料中,保温效果比较好的是.
①根据这一特点,时间为30min时,棉絮组的水温可能是下列选项中的哪一个.
A、46℃ B、43℃ C、39℃ D、36℃
②下列图象中能表示其温度T随时间t变化关系的.

they cleaning?
【查阅资料】蚁酸的主要成分是甲酸,甲酸的化学式为 HCOOH;甲酸溶于水,在一定条件下发生分解反应生成两种氧化物。
【提出问题】甲酸溶液是否具有酸性?
【实验与结论】向盛有甲酸溶液的试管中滴加紫色石蕊溶液,观察到溶液颜色变成红色,说明甲酸溶液显①性。
【提出问题】甲酸分解生成的两种氧化物是什么?
【推断与猜想】
⑴小组同学根据甲酸中含有氢元素,推测出生成物中含有水。
⑵他们对另一种氧化物提出两种猜想:
猜想①:二氧化碳; 猜想②:一氧化碳。
【实验与结论】
为了证明自己的猜想,他们将甲酸分解产生的气体通过如图所示的装置(铁架台已略去)。观察到的实验现象如下:
Ⅰ.装置 A 中澄清石灰水无明显变化。
Ⅱ.装置 C 中的黑色粉末变红色。Ⅲ.装置 D 中澄清石灰水变浑浊。
【实验结论】甲酸具有酸性,在一定条件下分解生成水和②。
【拓展延伸】人被蚊虫叮咬后,在其叮咬处涂抹③可减轻痛痒。
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Is food art of the holidays? |
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Liao Bo |
I think there is a really close connection (联系) between festivals and food. My dad is a businessman. He travels on business a lot. He even has to travel during holidays, like Mid—Autumn Festival. But he once told me that as long as he can eat my mom's homemade mooncakes, he can feel like he's at home with us. |
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Zhang Han |
Eating mooncakes during Mid—Autumn Festival drives me crazy! I really don't like the taste of mooncakes, but Mom forces me to eat them every year. But as I eat more mooncakes, I start to hate the holiday! This holiday should be held to celebrate some special person or event, not a food. I don't want this tasteless food to ruin (毁坏) holiday any more. |
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Chen Yuan |
In my opinion, eating traditional food during holidays is part of our culture. I remember one time during Lantern Festival, my parents were too busy to bring home any sweet dumplings. Although we still lit up our rabbit lantern that night, I still felt like the festival was not complete, since we didn't have my dumplings. |
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Yuan Hui |
In the past, people would usually save precious food for special days. But now, we can eat it whenever we want. I don't think it is important to eat traditional food during holidays anymore. We can still do some other things to celebrate, such as watching the moon during Mid—Autumn Festival or remembering Qu Yuan during Dragon Boat Festival. |