问题 选择题

如图所示是甲、乙两种物质的溶解度曲线.将t2℃时等质量的甲、乙两种物质的饱和溶液降温到t1℃时(  )

A.两种溶液仍是饱和溶液

B.两种溶液的质量仍相同

C.乙溶液的溶质质量分数比甲大

D.乙溶液中的溶剂质量比甲多

答案

A、乙的乙的溶解度随温度降低而增大,所以降温后变为不饱和溶液,故错误;

B、甲的溶解度随温度降低而减小,要析出晶体,溶液质量减小,乙的溶解度随温度降低而增大,溶液质量不变,故错误;

C、由B可知,甲降温后溶质减小,溶质的质量分数减小,乙中溶质、溶剂质量均不变,溶质的质量分数不变,与降温前相等,根据饱和时质量分数的计算式

溶解度
溶解度+100g
×100%,可知溶解度大则溶质的质量分数大,而t1℃时甲的溶解度大于t2℃时乙的溶解度,故降温后乙溶液的溶质质量分数比甲小,故错误;

D、t2℃时甲的溶解度大于乙 的溶解度,所以t2℃时等质量的甲、乙两种物质的饱和溶液中甲溶液中溶剂的质量比乙少,降温溶剂的质量不变,故正确;

故选D.

选择题
阅读理解

One day, when old Jacob and little Jacoble were walking home, the sun began to go down. Old Jacob was thinking of his house and little Jacoble didn’t know what to think. Then he thought of a wonderful idea, and he cried, “Jacob! Do you know what I saw yesterday? I saw a green rabbit. It was flying in the air and it was so big, even bigger than an elephant!”

“You saw that with your own eyes?” asked old Jacob. “Of course I did,” said Jacoble proudly. “It’s a good thing that you really saw that big, flying, green rabbit,” said old Jacob, “because that old bridge we are going to walk over is a very strange one. As soon as anyone who hasn’t told the truth comes on it, the bridge breaks in two.” They continued walking.

“Jacob,” said Jacoble a little later, “you know that big, green, flying rabbit I saw yesterday ... Well, it wasn’t really flying, and ... it wasn’t quite as big as an elephant ... but it was very big, about the size of a horse!” “Big as a horse?” asked Jacob as they got closer to the bridge and little Jacoble began not to feel so well.

“Jacob,” said Jacoble. “That big, green rabbit I saw yesterday, well, I had something in my eye and so I couldn’t see that well. It wasn’t a very big rabbit but it was green. Yes, that’s what it was — all green!”

Old Jacob didn’t say a word. He just walked over the bridge. But Jacoble didn’t go after him because he was afraid and he knew why he was afraid. He stood at the bridge and said, “Oh, Jacob! You know that rabbit I saw yesterday. It wasn’t green. No. It was just a little, brown rabbit.”

Then he was not afraid of anything any more and he ran happily over the bridge.

小题1:We know from the text that the story happened ______.

A.in the morning

B.in the afternoon

C.at dusk (黄昏)

D.at midnight小题2:Jacob considered Jacoble’s story ______.

A.humorous

B.interesting

C.frightening

D.unbelievable小题3:Why did little Jacoble change his story again and again?

A.Because he was afraid of falling into the river.

B.Because he tried to persuade Jacob to believe it.

C.Because he wanted to frighten Jacob.

D.Because he didn’t remember the story clearly.小题4:What lesson can we learn from the text?

A.A lie will never be known.

B.True friends don’t cheat each other.

C.Telling lies makes one suffer from fears.

D.Making up a story is lying.