问题 问答题

无土栽培的某种营养液中,含硝酸钾的质量分数为7.10%.

(1)某蔬菜生产基地欲配制该营养液400kg,需要硝酸钾的质量是多少?

(2)这些硝酸钾中含氮元素的质量是多少?

答案

(1)根据溶质的质量分数=溶质质量/溶液质量×100%,可求得配制该营养液400kg需要硝酸钾的质量为:400kg×7.10%=28.4kg;

(2)根据物质中某元素的质量分数=

该元素的相对原子质量×原子个数
该物质的相对分子量
×100%,

可求得硝酸钾氮元素的质量分数=

14
9+14+16×3
×100%=13.86% 溶质硝酸钾中含氮元素的质量=28.4kg×13.86%=3.94 kg.

故答案为:

(1)28.4kg;  

(2)3.94kg.

阅读理解

阅读理解 

         It’s Sunday. It’s fine. Tom does not go to school today. But he is not at home. He’s now sitting(坐) on a Chinese bus. He is going to the movie house. All his classmates(同学) will go to see a movie this afternoon. His teacher Mr Wang will go there, too. They will meet at 2:00 p.m. at the gate(门口) of the movie house.  

         An old man gets on(上车) the bus. Tom stands up and says(说) to the old man, “Come and sit here, please.” The old man goes over and sits down. He says, “Thank you very much, my boy. You are a good student.” Tom answers, “You’re welcome.”  

     “What school are you in?” the old man asks Tom.  

     “I am in No. 2 Middle School.” Tom answers.

     “No. 2? That’s a good school. My son is a teacher there. He is an English teacher.” The old man says.  

     “English teacher? Excuse me, grandpa. What’s your son’s name, please?” Tom asks.  

     “Mr Wang,” says the old man.  

     “Ah, ah, he is my English teacher.” Just then, the bus stops near the movie house. Tom says goodbye to the old man and gets off(下车) the bus. The old man smiles(微笑) to Tom.

1. In the sentence(句子) “the bus stops near the movie house”. “stop” means (意思是)______.  

A. 车站      

B. 开      

C. 关      

D. 停

2. Which(哪一句) is right?  

A. It's Saturday today.  

B. It's not fine today.  

C. Tom goes to school on Sunday.  

D. Tom is a student of No. 2 Middle School.

3. Mr Wang is_____. 

A. at home today  

B. the old man's son  

C. the old man's father  

D. a Chinese teacher

4. What do you think of Tom? 

A. Tom is a good student.  

B. Tom is a bad(坏的) student.  

C. He does wrong(错) things.  

D. He is a good teacher.

5. Which is right?  

A. Tom goes to the movie house on an English car.  

B. Only Tom and his teacher go to the movie house to see a movie.  

C. They go to the movie house for a meeting(会议).  

D. The old man's son is Tom's English teacher.

单项选择题