题目内容

【题目】下列有关溶液的说法中,正确的是(

A.已达到饱和的氯化钠溶液中不能再溶解其他物质

B.20时,50g水中最多溶解18g氯化钠,则20时氯化钠的溶解度为18g

C.任何物质的饱和溶液在升高温度时,一定会变成该物质的不饱和溶液

D.相同温度时,同种溶质的饱和溶液一定比它的不饱和溶液浓

【答案】D

【解析】已达到饱和的氯化钠溶液中不能再溶解氯化钠,但仍可以溶解其他物质,A错;溶解度指的是一定温度时,100g溶剂中最多溶解的溶质的质量,因此,根据20时,50g水中最多溶解18g氯化钠可知,20时氯化钠的溶解度为36g,B错;对于溶解度随温度升高而增大的物质,其饱和溶液在升高温度时,一定会变成不饱和溶液,而对于溶解度随温度升高而减小的物质,其饱和溶液在升高温度时,会析出晶体,所得溶液仍然是饱和溶液,C错.

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【题目】Lisa has an interesting hobby. She likes collecting stamps(邮票).She usually collects stamps after school. Now she has five hundred stamps from all over the world. And four hundred of them are in colour.

Lisa likes stamps with pictures of animals in them. In this way,she knows the names of many animals. She also borrows books about animals from her school library. She learns a lot about them.

Sometimes Lisa has many stamps of the same kind. So she usually gives them to her friends. Then they give her other stamps.

Lisa writes to her friends in many countries. She sends them stamps of her own country. And her friends send her stamps of their countries. Lisa's father also buys stamps for her. Many of Lisa's friends collect other things. Some collect coins(硬币)and others collect cards.

1How many colour stamps does Lisa have?

A. One hundred. B. Four hundred.

C. Five hundred. D. Nine hundred.

2Why does Lisa like stamps with pictures of animals in them?

A. Because she wants to feed some animals.

B. Because she can make much money.

C. Because she can know the names of many animals.

D. Because she will borrow some animals from her friends.

3Sometimes Lisa has many stamps of the same kind. She usually .

A. keeps them

B. throws them away

C. sells(卖)them to her friends

D. sends them to her friends

4Which of the following is TRUE according to the passage?

A. Lisa writes to her friends in many countries.

B. Lisa's mother often buys stamps for her.

C. Lisa's stamps are all in colour.

D. Lisa borrows books about stamps from her school library.

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