问题 选择题

两种固体物质a、b的溶解度曲线如图,下列说法正确的是(  )

A.b的溶解度小于a的溶解度

B.分别将t2℃时a、b两种物质的溶液降温至t1℃时,肯定都有晶体析出

C.要从b溶液中得到较多的b晶体,通常可采用降温结晶的方法

D.在t2℃时,a、b两种固体的溶解度相等

答案

A、要比较物质的溶解度大小,须限定温度,否则无法比较,如:温度大于t2℃时a的溶解度大于b的溶解度,t2℃时二者的溶解度相等,温度小于t2℃时a的溶解度小于b的溶解度,故错误;

B、由于不知t2℃时a、b物质的溶液是否为饱和溶液,故将 t2℃时a、b物质的溶液降温到t1℃溶液的状态无法判断,故无法判断是否有晶体析出,故错误;

C、由图可知:b的溶解度都随温度的升高变化不大,所以要从b溶液中得到较多的b晶体,通常采用蒸发溶剂的方法,故错误;

所以t1℃时,二者饱和溶液溶质的质量分数也相等;将a、b两种物质的饱和溶液升温至t2℃,变为不饱和溶液,溶质和溶剂的质量不变,则所得a、b两种物质的溶液中溶质质量分数与t1℃时相同,故所得a、b两种物质的溶液中溶质质量分数相相等,正确;

D、由图可知:t2℃时,两物质的溶解度曲线相交于一点,所以该温度下两种固体的溶解度相等,正确;

故选D.

阅读理解

One year our family decided to have a special celebration of Mother’s Day, as a token of appreciations for all the sacrifices that Mother had made for us. After breakfast we had arranged, as a surprise, to hire a car and take her for a beautiful drive in the country. Mother was rarely able to have a treat like that, because she was busy in the house nearly all the time.

But on the very morning of the day, we changed the plan a little, because it occurred to Father that it would be even better to take Mother fishing. As the car was hired and paid for, we might as well use it to drive up into the hills where the streams are. As Father said, if you just go driving without object, you have a sense of aimlessness, but if you are going to fish there is a definite purpose that heightens the enjoyment.

So we all felt it would be nicer for Mother to have a definite purpose . Father had just got a fishing rod the day before, which he said mother could use if she wanted to. Only Mother said she would much rather watch him fish than try to fish herself.

So we got her to make up a sandwich lunch in case we got hungry, though we were to come home again to a big festive dinner.

Well, when the car came to the door, it turned out that there was not as much space in it as we had supposed. It was plain that we couldn’t all get in.

Father said that he could just stay home and put in the time working in the garden. He said that there was a lot of rough dirty work that he could do, like digging a trench for the garbage, which would save hiring a man, and so he said that he’d stay home; he said that we were not to let the fact that he had not had a real holiday for three years stand in our way. He wanted us to go right ahead and not to mind him.

But of course we all felt that it would never do to let Father stay home, especially as we knew he would make trouble if he did. The two girls, Anne and Mary, would have stayed and helped the maid get dinner, only it seemed such a pity,for the two girls were eager to show their new hats on a lovely day like this. But they said that Mother had only to say the word and they’d gladly stay home and work. Will and I would have dropped out, but unfortunately we wouldn’t have been any use in preparing the dinner.

小题1:The author’s family decided to celebrate Mother’s Day specially to _______.

A.show love for their mother

B.show gratitude to their mother

C.show respect for their mother

D.to make up for a previous appointment小题2:According to Paragraph 2, we know that the plan was changed because________.

A.Father proposed to go fishing out

B.we thought that driving out is boring

C.we failed to hire a car to go out

D.the car was not big enough小题3:What problem did we find when the car arrived?

A.The car was too old to drive on mountain roads.

B.The car was larger than we expected.

C.The car was too small to accommodate us all.

D.The car was too plain looking.小题4:Why didn’t the author drop out of the activity?

A.Because his sisters didn’t join in.

B.Because he needed to have dinner.

C.Because he couldn’t cook the dinner.

D.Because he hadn’t had a real holiday for three years.小题5:Which of the following proverbs describes the text best?

A.Everything comes to him who waits.

B.Changes always go beyond plans.

C.Better late than never.

D.Once on shore, one prays no more.

问答题 案例分析题