题干

将一质量为5kg,体积为6×10-3m3的西瓜浸没水中,西瓜受到的浮力是____ N,松手后西瓜会____ (上浮/下沉)。(g取10N/kg)

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答案(点此获取答案解析)

60,上浮

同类题2

为了减少CO对大气的污染,某学习小组拟研究CO和H2O反应转化为绿色能源H2

(1)已知:2CO(g)+O2(g)═2CO2(g);△H=﹣566kJ•moL﹣1

2H2(g)+O2(g)═2H2O(g);△H=﹣483.6KJ•moL﹣1

H2O (g)═H2O(l);△H=﹣44.0KJ•moL﹣1

写出CO和H2O(g)作用生成CO2和H2的热化学方程式____ 

(2)在850℃时,反应:CO(g)+H2O(g)⇌CO2(g)+H2(g)的K=1.

①:若升高温度到950℃时,达到平衡时K____ 1(填“>”、“<”或“=”).

②:850℃时,若向一容积可变的密闭容器中同时充入1.0mol CO,3.0mol H2O,1.0mol CO2和x mol H2,若要使上述反应开始时向正反应方向进行,则x应满足的条件是____ 

③:在②的条件下,按下列加料方式加料,达到平衡时H2的体积分数如下:


加料方式/mol

H2的体积分数

物质

CO(g)

H2O(g)

CO2(g)

H2(g)

加料一

1

3

0

0

a%

加料二

0

1.2

0.6

0.6

b%

则:a____b(填“>”、“<”或“=”).

(3)H2是一种理想的绿色能源,可作燃料电池.

①若该氢氧燃料电池以KOH为电解质溶液,其正极的电极反应式是____ 

②在25℃时,以氢氧燃料电池为电源,用石墨电极电解1000mL一定浓度的CuSO4溶液.5min后电解完全,在一个石墨电极上只有1.28g Cu生成.试回答下列问题:

电解的总反应式为____ 

电解过程中转移的电子数为____ mol,同时生成标准状况下气体的体积为____ L

同类题3

阅读下面短文,从短文后各题所给的A、B、C、D四个选项中选出能填入空白处的最佳选项。

    I used to live in my own room alone. But one day it all changed when my brother Jack asked to share my 1. At first, my parents said “no” to him, but at last my mother agreed. I cried and asked my parents not to do this, 2 it didn't work.

    As soon as Jack entered (进来) my room, it began to become 3. To my anger, he often left his unwashed clothes and toys everywhere!

    One evening, I was doing some 4 on my computer while Jack was listening to music.5, I left my seat to get some water. A big surprise was waiting for me when I 6. He was using my computer to play games. I had forgotten to save (保存) the homework. Sadly, he had closed my program 7 saving it—all I had done had disappeared (消失)! I 8 him. He cried a lot as my mother came and beat him. My mother also asked him to leave my room at once.

    Then I did my homework 9. At 10:00 pm. I finished it. When I was going to turn off the 10, I saw the photo of my 11 that he had put on my table. I looked at his lovely face and remembered how 12 he was when my mom beat him. I really felt 13. I went to see what he was doing. I found he was 14 in my parents' bed. I kissed his face. He woke up, got up and said, “I'm sorry. I won't bring you any more trouble.”

    I was so moved (感动的) and said, “From now on, my room is not only mine. It is 15!” That very night, Jack and I shared not only the room, but the bed.