问题 选择题

镁铁混合物4.9g,溶解在过量某浓度的稀硝酸中,完全反应得到标况下气体2.24L(假设气体全为NO),则向反应后的溶液中加入足量的烧碱,则可生成沉淀的质量为( )

A.6g

B.8g

C.10g

D.12g

答案

答案:C

设镁的物质的量为x,铁的物质的量为y,标况下2.24L气体的物质的量为0.1mol,则可得24x+56y=4.9g①;再根据氧化还原反应过程中得失电子数相等可得:2x+3y=0.1×(5—2)②;由①②可得x=0.0525;y=0.065mol;由元素守恒可得加入足量烧碱后,生成的氢氧化镁的物质的量为0.0525;生成的氢氧化铝的物质为0.065mol,从而可得总沉淀质量为10g;

阅读理解

Do you know of anyone who uses the truth to cheat? When someone tells you something that is true, but leaves out (略去) important information that should be inside, he can give you a false picture.

For example, someone might say, “I just won a hundred dollars on the lottery( * * ). It was great. I took that dollar ticket back to the store and turned it in for one hundred dollars!”

This guy is a winner, right? Maybe, maybe not. We then discover that he bought $ 200 worth of tickets, and only one was a winner. He’s really a big loser!

He didn’t say anything that was false, but he left out important information on purpose. That’s called a half-truth. Half truths are not technically lies, but they are just as dishonest.

Some politicians (政客) often use this trick. Let’s say that during Governor Smith’s last term, her state lost one million jobs and got three million jobs. Then she tries to get another term. One of her opponents (竞争对手) says, “During Governor Smith’s term, the state lost one million jobs!” That’s true. However, an honest statement would have been, “During Governor Smith’s term, the state had increased two million jobs.’’

Advertisers will sometimes use half–truths. It’s against the law to make false statements so they try to mislead you with the truth. An advertisement might say, “Nine out of ten doctors advised their patients to take Yucky Pills to cure toothache.” It fails to say that they only asked ten doctors and nine of them work for the Yucky Company.

This kind of cheating happens too often. It’s a sad fact of life: Lies are lies, and sometimes the truth can lie as well.

小题1:We may infer that the author believes people should ________.

A.buy lottery tickets if possible

B.make use of half–truths

C.be careful about what they are told

D.not trust the Yucky Company小题2:How many examples does the writer give to show how the truth is used to cheat?

A.One

B.Two

C.Three

D.Four小题3:Which of the following is TRUE according to the passage?

A.Using half truths is against the law.

B.Technically, half truths are in fact lies.

C.Yucky Pills is a very good medicine for toothache.

D.Governor Smith did a good job during her last term.小题4:Which of the following best expresses the main idea of the passage?

A.He’s really a big loser!

B.Sometimes the truth can lie as well.

C.Advertisers will sometimes use half truths.

D.It’s against the law to make false statements.

单项选择题