问题 选择题

下列有关实验的说法不正确的是

A.当沉淀的颗粒较大时,也可用倾析法将固体和溶液分离

B.结晶时,若溶质的溶解度越大,或溶液的浓度越高、或溶剂的蒸发速度越快,析出的晶粒就越细小

C.利用硝酸和硝酸银溶液可区分工业盐和食盐

D.制备阿司匹林时可能混有少量的聚合物杂质,可用碳酸氢钠溶液进行提纯

答案

答案:B

倾析法就是从液体中分离密度较大且不溶的固体的方法,A正确。析出的晶粒大小与溶质的溶解度或溶液的浓度无关,而与溶剂的蒸发速度有关,B不正确。工业盐是亚硝酸钠,C正确。阿司匹林分子内存在羧基与碳酸氢钠反应,因而可以提纯。答案是B。

阅读理解

阅读理解。

     Look at this picture. The girl with a toy in her hands is my little sister Susan. She is only four years

old. Look! She is playing with her toy happily (高兴地). She likes her toy very much and she calls it

Kelly. The woman near Susan is my mother. She is reading a book carefully (仔细地) on the sofa.

She always likes reading and watching TV. Can you see a man on the sofa? He is my father. He is

reading a newspaper now. It is his favorite. The boy between my father and mother is me. I am Tom.

I am playing the piano carefully.

1. How many people are there in the picture?        

A. Three.                 

B. Four.        

C. Five.                   

D. Six.

2. What is Susan doing?        

A. She is talking with her mother.       

B. She is playing the piano.        

C. She is reading a storybook.        

D. She is playing with Kelly.

3. What's Tom's mother doing?       

A. She is watching TV.        

B. She is reading a newspaper.        

C. She is reading a book.        

D. She is playing with her daughter.

4. What does Tom's father like doing best?        

A. Reading books.        

B. Reading newspapers.        

C. Watching news on TV.        

D. Playing tennis.

5. Where is Tom?         

A. He is near the window.         

B. He is sitting on the chair.         

C. He is sitting between his father and mother.        

D. He is near his sister.

多项选择题