问题 单项选择题

.将一块严重腐蚀而部分变成铜绿[化学式为Cu2(OH)2CO3]的铜块磨成粉末,在空气中充分灼烧成CuO,发现固体质量在灼烧前后保持不变,则灼烧前粉末中铜(单质)的质量分数为( )。

A.52.8%

B.50.0%

C.47.2%

D.46.3%

答案

参考答案:A

解析:由铜绿分解的化学方程式Cu2(OH)2CO3 △2CuO + H2O ↑+ CO2↑可以知道,灼烧时减少的是"H2O 和CO2"的质量,增加的是铜变成氧化铜时氧的质量,二者增减相同,1 mol碱式碳酸铜就减少1 mol H2CO3的质量,则增加的氧的量就是62 g,即3.875 mol氧,也就是3.875 mol铜,所以铜原来有248 g。计算得原混合物质量为470 g,铜的质量分数是52.8%。

阅读理解

If someone says to you: “ Give me five”, do not search your pocket to get five yuan! It will make others laugh! The person’s not asking for your money, but your fingers.

In the US, “ give me five” or “ give me the high five” is a popular gesture ( 动作 ). You can see it often in films or on TV. It means the clapping ( 拍  ) of each other’s raised right hands together.

People do it when they meet for the first time or something happy happens. For example, a student has good marks in exams or wins a lottery ticket ( * *   ). If a football team wins a game, the players will give high fives to everyone around to celebrate.

This gesture may come from the old Roman gesture of raising the right arm for the king. This showed that the person raising his arm did not have a sword ( 剑 ) in his hand.

Why not try to give the high five to your friends?

小题1:“ Give me five” is a gesture to ______________.

A.ask for money

B.celebrate success

C.search one’s pocket

D.play小题2:The gesture “ give me five” is the clapping of _________.

A.toes

B.hands

C.arms

D.legs小题3:When you ________, you give your friends high fives.

A.lose your money

B.go back home

C.win a football game

D.do badly in exams小题4:The gesture started in _______ according to the story.

A.Rome

B.America

C.China

D.Britain小题5:Why did the Romans raise the right arm for the emperor?  Because ________.

A.they were proud of their emperor

B.they were happy to see the emperor

C.they wanted to show there were no swords in their hands

D.We don’t know

名词解释