问题 问答题

某地一不法商贩销售的“尿素”中,经检验含氮的质量分数为28%.求:

(1)已知尿素的化学式为CO(NH22,则尿素中氮元素的质量分数是多少?(精确到0.1%)

(2)该商贩所售每袋“尿素”(50kg)中,实际含尿素多少千克?

答案

(1)尿素中氮元素的质量分数

14×2
12+16+14×2+1×4
×100%=46.7%

(2)50kg×28%÷46.7%=30kg

答:尿素中氮元素的质量分数约为46.7%;实际含尿素30kg.

阅读理解

阅读理解。

     Mrs. Hunt comes back from work. She tells Mr. Hunt about a nice dress. "I see it in the shop every

day." she says. "And...."

    "And do you want to buy it?" asks Mr. Hunt. "How much is it?"

    "It's  two  hundred  and  sixty  dollars,"Mrs. Hunt answers.

    "Is two hundred and sixty dollars for a dress? That's too much!"says Mr. Hunt.

    But every evening when she comes back, Mrs. Hunt only talks about the dress. So at last Mr. Hunt

says , "Oh , you can buy it! Here's the money! ". Mrs. Hunt is very happy. The next evening, Mr. Hunt

wants to have a look at the nice dress, but Mrs. Hunt says. "I don't want to buy it. "

     "Why not?" he asks.

     "Well, it is still in the window of the shop after a week. So I think no one wants this dress. And I

don't want it, either."

1. Mrs. Hunt sees the nice dress ______.     

A. at a bus stop     

B. in her factory     

C. in a shop

D. at her friend's home

2. Mrs. Hunt tells Mr. Hunt about the dress because she wants him to ______.     

A. have a look     

B. buy it for her     

C. make one like that

D. borrow it from the shop

3. Mr. Hun thinks the dress in the shop is ______.     

A. very small     

B. too long     

C. very cheap

D. too expensive

4. Which of the following is RIGHT?      

A. Mr. Hunt doesn't want his wife to buy the dress.     

B. Many other people also want the dress.     

C. Mrs. Hunt likes another dress in the shop.

D. Mr. and Mrs. Hunt come back from work together (一起) every day.

5. Mrs. Hunt doesn't want to buy the dress at last because she thinks ______.     

A. it is much too expensive     

B. it is not very new     

C. it is much too old

D. it is not very good

不定项选择