问题 填空题

人民币采用的光学变色防伪油墨中含氟化镁(MgF2),其中氟元素的化合价为       ;防伪油墨中还有一种胆固醇,其化学式为C27H46O ,则胆固醇中碳、氢、氧元素的原子个数比为          ,胆固醇的相对分子质量是           

答案

-1(或负一); 27:46:1

(答错1个数字得0分) , 386

在MgF2中,Mg元素的化合价为+2价,设F元素的化合价为x,则根据化合物中正负化合价的代数和为0,得(+2)+x×2=0,解得x=-1;

1个胆固醇分子是由27个碳原子、46个氢原子、1个氧原子构成的;相对分子质量=27×12+46+16=386;

点评:本题主要考查化学式的意义、根据化学式确定组成物质元素之间的质量关系以及有机物的定义.

阅读理解

The clock struck eleven at night. The whole house was quiet. Everyone was in bed except me. Under the strong light, I looked sadly before me at a huge pile of that troublesome stuff they call “books”.

I was going to have my examination the next day. “When can I go to bed?” I asked myself. I didn’t answer. In fact I dared not.

The clock struck twelve.” Oh, !” I cried. “Ten more books to read before I can go to bed!” We pupils are the most wretched creatures in the world. Dad does not agree with me on this. He did not have to work so hard when he was a boy.

The clock struck one. I was quite desperate(绝望的) now. I forgot all I had learned. I was too tired to go on. I did the only thing I could. I prayed, “Oh, God, please help me pass the exam tomorrow. I do promise to work hard afterwards, Amen.” My eyes were so heavy that I could hardly open them. A few minutes later, with my head on the desk, I fell asleep.

小题1:When the author was going over his lessons, all the others in the house were____.    

A.asleep

B.outside

C.working in bed

D.quietly laughing at him小题2:The underlined word “wretched” in Paragraph 3 probably means____.

A.very happy

B.disappointed

C.very unhappy

D.hopeful小题3:Reviewing his lessons didn’t help him because______.

A.it was too late at night

B.he was very tired

C.his eyes lids were so heavy that he couldn’t keep them open

D.he hadn’t studied hard before the examination小题4: What do you suppose happened to the author?

A.He went to a church to pray again.

B.He passed the exam by luck.

C.He failed in the exam.

D.He was punished by his teacher.小题5:The best title for the passage would be____.

A.The Night Before the Examination

B.Working Far into the Night

C.A Slow Student

D.Going Over My Lessons

填空题